tr 2018-2019 Projects Archives | Keck Geology Consortium
Assessing vegetation and fluvial responses to the PETM

Assessing vegetation and fluvial responses to the PETM

Assessing vegetation and fluvial responses to the Paleocene-Eocene Thermal Maximum in the Hanna Basin (Wyoming, U.S.A.)

Overview: This project focuses on developing the basin evolution and paleobotanical history of the Hanna Basin spanning the transition between the Paleocene and Eocene epochs. Globally a greenhouse climate state dominated the early Paleogene, and in the Western Interior of the United States the Laramide Orogeny produced a series of uplifts and sedimentary basins. Overall the paleoclimate appears to become drier and potentially more seasonal between the Paleocene and Eocene, likely related to global warming trends and changing topography due to uplift of the Rocky Mountains. In several basins there are attendant shifts in fluvial and floodplain deposition indicating drier and more seasonal conditions as well as moderate shifts in floral communities. However, the Hanna Basin of south-central Wyoming appears anomalous. Initial studies suggest this area remained largely wet and humid, defying regional trends. This uniqueness is particularly important because the basin likely contains one of the most stratigraphically-expanded records of the Paleocene-Eocene Thermal Maximum (PETM) of anywhere in the world.

Searching for fossil ferns in the Hanna Basin, Wyoming

The PETM is an abrupt global warming event linked to the massive release of carbon into Earth’s atmosphere and oceans (McInerney & Wing, 2011). In other basins in the Rocky Mountain region it is correlated to substantial changes in the hydrologic cycle exacerbating seasonality in rainfall and vegetation overturn (Wing et al., 2005; Foreman et al., 2012; Kraus et al., 2015). The effects in the Hanna Basin are largely unknown and may be unique in their character. Student projects will focus on one of three topics: (1) reconstruction of paleoenvironment from fluvial and floodplain deposits and recovering information on ancient landscape dynamics; (2) understanding the interacting components of the local to global carbon cycle through stable carbon isotope records; and (3) characterizing vegetation cover spanning the short- and long-term climate changes using a new plant cuticle-based proxy method.

When: July 6 – August 5, 2018

Where: Laramie, Wyoming (introduction and lab work) and Hanna, Wyoming (field work)

Who: Four to six students and project leaders Dr. Brady Foreman (Western Washington University, and Dr. Ellen Currano (University of Wyoming, USGS stratigrapher Marieke Deschesne and Field Museum paleobotanist Dr. Regan Dunn will also take part in field and lab work and provide additional mentorship for student projects.

Prerequisites and Recommended Courses: Suggested (but not required) are core courses in the Geology major: Historical Geology, Structure/Tectonics, Stratigraphy, Mineralogy, Paleontology and Geochemistry. Students should have completed key cognate courses in Chemistry and Math. Experience at a field camp or in a field geology course is recommended but not required.  We are particularly interested in applicants with an interest in Paleoclimates, who have a high degree of comfort in rugged outdoor settings, are able to hike several miles in warm temperatures (on occasion greater than 95° F in the high desert climate), are flexible eaters, and who want to use this work to complete a senior thesis (or equivalent) in geology. Helpful, but not required in the letter of recommendation from the on-campus sponsor is an indication of how well the applicant will function in a remote field setting with primitive camping (i.e., no running water, no bathrooms, limited cell phone service).

Expectations and Obligations:

  1. Participation in all project-related work during the summer (July 6-August 5, 2018).
  2. Follow up data analysis at home institution and regular conference calls with research team throughout academic year.
  3. Write an abstract and present a paper (poster or talk) for the Geological Society of America Rocky Mountain Section meeting in Manhattan, Kansas (conference is March 25-27, 2019).
  4. Write a short contribution (4-6 pages text + figures) to be published in the Proceedings of the Keck Geology Consortium 2019 Volume (first draft due Mid-February).
  5. Expected but not required: Use this work for the completion of a senior thesis (or equivalent) at your home institution.


Geologic Overview

The Paleocene-Eocene Thermal Maximum is viewed as one of the premier geologic analogs for modern, anthropogenic global warming. However, our understanding of the major terrestrial impacts is limited to one well-documented example (Bighorn Basin of northwest Wyoming) and a few other locations globally where only a few key hydrologic or temperature constraints exist. Broadly speaking, the terrestrial response to elevated carbon dioxide levels is expected to be highly variable due to topographic variability and shifting atmospheric circulation patterns under different latitudinal thermal gradients. As such it is critical to develop additional continental locations where the temperature, hydrologic, and biologic changes are constrained. The Hanna Basin is a logical extension of the work in the Bighorn Basin, and, more importantly, a key example for changes that may mimic those predicted for modern river and vegetation systems during future anthropogenic climate change.

The Hanna Basin record is a particularly important complement to the record already collected in the Bighorn Basin because stratigraphic data suggest a difference in water availability between the two basins. Both the PETM interval and the entire early Eocene sequence preserved in the Willwood Formation in the Bighorn Basin contain abundant red beds, indicative of well-drained soils and seasonal precipitation (Kraus and Riggins, 2007; Kraus et al., 2015). The Bighorn Basin records the consequences of a semi-arid basin experiencing an abrupt global warming event. In contrast, the Hanna Basin sedimentary sequence remains drab-colored and coal-rich from bottom to top, suggesting that wet, swampy conditions prevailed through the PETM and early Eocene (Dechesne et al., in prep). It records the consequences of a more humid basin experiencing an abrupt global warming event. Thus, comparisons of the Hanna and Bighorn basins will allow us to disentangle the roles of temperature and water availability in driving vegetation change and the fluvial response in a dominantly humid setting. This water availability difference is likely due to the location of the Hanna Basin, farther to the east and potentially more proximal to moisture sources as compared to the Bighorn Basin (Sewall & Sloan, 2006). The Laramide Orogeny created a complex topography within the Western Interior that strongly influenced water vapor transport paths (Sewall & Sloan, 2006). In general, however, circulation models suggest the easternmost Laramide basins were wetter as moisture from the paleo-Gulf of Mexico moved north and westward. This resulted in semi-arid and dry conditions in the western and northernmost Laramide basins (Sewall & Sloan, 2006).

Figure 1: Cretaceous to Eocene sedimentary strata of the Hanna Basin, Wyoming.

Study Area

The targeted field area for this study is the Hanna Basin of south-central Wyoming near the small town of Hanna. The Hanna Basin is a Laramide style basin bounded by the Rawlins uplift to the west, Sweetwater Arch in the north, the Simpson Ridge anticline in the east, and the Medicine Bow and Sierra Madre Mountains in the south. It is exceptional among the Laramide basins because of its high subsidence rate, extremely thick Cretaceous to Eocene sedimentary strata, and extensive coal deposits (Dobbin et al., 1929; Roberts and Kirschbaum, 1995; Wroblewski, 2003). The Paleocene-Eocene boundary is preserved in the Hanna Formation, which is over 2000 meters thick at the center of the basin (WOGCC, 2016; Gill et al., 1970; Wrobleski, 2003) and consists of conglomerates, sandstones, siltstones, carbonaceous shales, and coals. These deposits are interpreted as low gradient fluvial to paludal and lacustrine (Dobbin et al, 1929; Wrobelski, 2003; Lillegraven et al., 2004). The student projects will target a specific set of extensive outcrops along the Hanna Draw Road and in “The Breaks,” which have been the focus of new geologic and paleontologic work by Currano, Dechesne, and Dunn. The majority of research will focus on a 250-meter thick stratigraphic interval with pollen biostratigraphic constraints and initial bulk d13C values that indicate the PETM is preserved.

Goals and Significance of the Project

Overall the goal of the project is to characterize fluvial and vegetation changes spanning the transition between the Paleocene and Eocene epochs in the Hanna Basin of Wyoming. This is a critical time period in the history of life and the evolution of the Rocky Mountain region. Specifically, there were transitory changes in paleo-plant communities, persistent shift in the mammalian biogeography, and a general warming and drying trend in the Western Interior of the United States. The Hanna Basin potentially records the most complete history of this transition because it witnessed the fastest sedimentation rates of any Laramide basin in the region. This broad goal requires (1) refining the chronstratigraphy of the basin using pollen fossils and carbon isotope records; (2) detailed lithofacies analysis and outcrop mapping; and (3) application of new cuticle-based proxies for vegetation cover.

Student Projects

Student projects will be sub-divided into three discipline related groups. These groups entail Sedimentology-, Geochemistry-, and Paleobotany-themed projects. All students will receive training and gain experience in the three disciplines, and interact extensively with other students, faculty, and collaborators. However, the specific projects they pursue will fall into one of these three categories. Sedimentology projects will involve detailed lithofacies analysis and paleoenvironmental reconstructions of the river and floodplain deposits (n = 1 student project). These students will develop field datasets that address key questions regarding river channel morphology, avulsion behavior, floodplain drainage, and overbank flooding frequency. The majority of data can be derived from the detailed stratigraphy section we will measure at Hanna Draw area. A separate Sedimentology project (n = 1 student project) will focus on mapping out and describing the larger alluvial architecture of the fluvial sandbodies. This entails identifying and tracing out the amalgamation of distinct channel occupation events and the lateral migration of channel bodies. This information will yield insights into the mobility and paleo-dynamics of the ancient river systems.

The Geochemistry-themed projects will focus on developing a detailed δ13C bulk organic isotope stratigraphy through the 250 meters of section thought to contain the PETM (n = 2 student projects). This will entail a combination of stratigraphic section measuring (fieldwork), and sample preparation at the University of Wyoming. This includes powdering rock samples, acid digestion, and distilled water treatments, followed by drying and weighing steps. Time permitting students will run samples themselves on the Isotope Ratio Mass Spectrometers at the University of Wyoming Stable Isotope Facility. Two students will focus on this component of the project. One student will recover secular variation from densely sampled (every 0.5 m or finer) vertical samples distributed throughout the 250-meter target interval. A second student will focus on constraining lateral variability of the isotope signals. Since bulk organic δ13C records mix vegetative matter from several different types of plants it is important to constrain the total amount of variability across a landscape. This is rarely done in ancient strata (Magioncalda et al., 2004; Foreman et al., 2012), and this student will produce one of the most detailed evaluations of this uncertainty to date.

Paleobotany-themed projects will utilize a new proxy for vegetation cover that uses leaf epidermal cell size and shape to reconstruct leaf area index (LAI=foliage area/ground area; Dunn et al., 2015). This proxy has been effectively used to correlate changes in vegetation cover in South America to environmental changes, as well as to vertebrate evolution. The work in the Hanna Basin will be the first attempt to quantitatively document changes in vegetation structure across the Paleocene-Eocene boundary. The samples contain fragments of fossil leaf cuticle that preserve epidermal cell morphology. Students will photograph cuticle fragments using the microscope set-up in Currano’s lab, measure leaf epidermal cell size and shape using a Wacom Cintiq tablet and ImageJ, and reconstruct LAI using regression equations between size and shape parameters and LAI produced by Dunn from using a modern calibration datasets (Dunn et al., 2016). One student will analyze the vertical transect and a second will analyze a set of lateral samples by tracing out a stratigraphic marker bed over several 100’s of meters. This approach will allow both temporal and spatial changes in vegetation to be constrained.

Summary of Projects

Student 1: Lithofacies analysis of fluvial and overbank facies

Student 2: Mapping and description of sandbody geometries and floodplain relationship

Student 3: δ13C bulk organic isotope stratigraphy vertical variation

Student 4: δ13C bulk organic isotope stratigraphy lateral variation

Student 5: Cuticle variability and vegetation cover, vertical section

Student 6: Cuticle variability and vegetation cover, lateral section

Figure 2: Measuring section using a Jacob’s staff.


The planned projects will involve 4-6 undergraduate students at junior and senior levels in their academic career. Students and faculty will rendezvous at the University of Wyoming on July 6 where initial gear checks will occur, and safety procedures and project details will be presented by faculty members. After this orientation we will proceed to the field area near Hanna, Wyoming (~2 hour drive). Field transport will include a rented university vehicle and two private vehicles. The field area is remote, but camping will occur in close proximity to vehicles. Our camp will be set up on public (BLM) lands, and will be primitive (i.e., no running water, no toilets, limited cell phone service). The first field day will entail a tour of the study area, an overview of the depositional history of the basin, and an additional field safety orientation. Subsequently, the students will be subdivided into the sedimentology, geochemistry, and paleobotany research groups and begin their projects. The remainder of the time will be divided into four phases:

Phase 1 (07/07 thru 07/14): Fieldwork

  • main stratigraphic section measuring (3 students)
  • outcrop mapping (1 students)
  • paleobotanical excavation (2 students)

Phase 2 (07/15 thru 07/23): Field and Lab work

  • main stratigraphic section measuring & outcrop mapping (2 students)
  • paleobotanical excavation (2 students)
  • geochemistry sample preparation (2 students)

Phase 3 (07/24 thru 08/05): Field and Lab work

  • main stratigraphic section measuring/outcrop interpretation (2 students)
  • paleobotanical proxy training (2 students)
  • geochemistry sample preparation (2 students)

Phase 4 (March, 2019): Professional Development Component

  • poster presentations at Rocky Mountain Section GSA meeting

The expectations for students include (1) a positive, flexible attitude, (2) a responsiveness to the needs of the group, (3) a collaborative mentality, (4) strong work ethic, and (5) interest in developing quantitative and interpretative skills. These will be rough working conditions. Temperatures can exceed 95º F in the high desert climate of Wyoming. Strong winds and intense rainstorms are also likely. Students will be expected to have appropriate field gear (e.g., boots, hat, sunglasses, tent, sleeping bag, sleeping pad, backpack, water bottles). Students will need to be physically fit, and able to walk several miles per day on steep slopes in the heat, dig quarries that requires the use of shovels and pickaxes, and be capable of carrying and packing out over 30 lbs of rock per day over 3 miles. Days will likely be long, in excess of eight hours. Dietary restrictions will be accommodated if possible. Each research sub-group will be expected to produce a cohesive presentation for the annual Rocky Mountain Section meeting of GSA in May 2019 (location of meeting is unannounced). Faculty advisors will coordinate with the students towards this endeavor and aid in the construction of the poster presentation. All students will be expected to attend the meeting and participate in associated activities.


As with any field and lab work there will be safety concerns. Field risks include dehydration, heat stroke, exhaustion, sunburn, insect bites, poisonous snakes, and physical injuries such as sprained ankles and broken bones. Lab risks are relatively minor, but include the use of (weak) acids when preparing stable isotope samples and airborne dust respiratory concerns when handling and preparing plant fossils. Risks will be mitigated by following proper training protocols, outlining and identifying the risks, and holding several safety meetings. Faculty associated with the project have extensive experience in all pertinent field and lab methodologies, wilderness first aid training, and will coordinate with lab technicians to maintain safety standards.

The faculty members involved in this project and collaborators collectively have over 30 field seasons of experience working in the region. They have published over 15 scientific articles and reports on the field area and equivalent rocks in the Laramide basins of the western United States. All have led several field crews of undergraduate and graduate students under similar circumstances. Foreman and Dechesne are certified in wilderness first-aid, and we will be maintaining a list of nearby medical facilities in case of emergency. In terms of professional expertise Dr. Brady Foreman (WWU) and Marieke Dechesne (USGS) are sedimentary geologists who have worked extensively in the surrounding Laramide and Sevier foreland basin deposits. Dr. Ellen Currano (University of Wyoming) and Dr. Regan Dunn (Field Museum) are paleobotanists who have worked extensively on cuticle and plant macrofossil records in the region. Dechesne, Dunn, and Currano have collected the initial datasets upon which this proposal is based, and have identified specific areas in the basin to target for this study. This will maximize the chances of research success for the students. Foreman and Dechesne will advise students with sedimentologic projects, paleobotany projects will be advised by Currano and Dunn, and geochemistry projects will be advised by Foreman and Currano.

Figure 3: Cnemidaria fern fossil.


We plan to take all participants to the GSA Rocky Mountain section meeting in Manhattan, Kansas (25–27 March 2019).  We hope most students will be first author on one paper, and probably secondary authors on others due to the collaborative nature of the project.

All students are required to complete a 4-6 page paper (short contribution) that will be published in the Proceedings of the Keck Geology Consortium 2019 Volume (see examples from previous years). The first draft of this paper will be reviewed by your research advisor at your home institution sometime in late February, 2019, with the revised version sent to the project directors by March 1.  Final versions of your paper and figures will be submitted to the Keck Office in Mid-March.


Bataille, C.P., Watford, D., Ruegg, S., Lowe, A., Bowen, G.J. 2016. Chemostratigraphic age model for the Tornillo Group: A possible link between fluvial stratigraphy and climate. Palaeogeography, Palaeoclimatology, Palaeoecology 457: 277-289.

Bowen, G.J., Bowen, B.B. 2008. Mechanisms of PETM global change constrained by a new record from central Utah. Geology 36: 379-382.

Clechenko, E.R., Kelly, D.C., Harrington, G.J., Stiles, C.A. 2008. Terrestrial records of a regional weathering profile at the Paleocene-Eocene boundary in the Williston Basin of North Dakota. GSA Bullletin 119: 428-442.

Dechesne, M., Currano,  E.D., Dunn, R.E., Higgins, P., Hartman, J., Chamberlain, K. (in preparation). Climatic and tectonic responses of the fluvial to paludal strata of the Hanna Formation around the Paleocene-Eocene Boundary, Hanna Basin, Wyoming.

Dobbin, C.E., Bowen, C.F., Hoots, H.W. 1929. Geology and coal and oil resources of the Hanna       and      Carbons basins, Carbon County, Wyoming. U.S. Geological Survey Bulletin 804: 88.

Dunn, R. E., C. A. E. Strömberg, R. H. Madden, M. J. Kohn, and A. A. Carlini. 2015. Linked canopy,          climate, and faunal change in the Cenozoic of Patagonia. Science 347(6219):258-261.

Dunn RE, Barclay RS, Currano ED. 2016. Using leaf epidermis to unlock the ancient forest   reconstruction enigma. Geological Society of America Annual Meeting Abstract, Denver, CO.

Foreman, B.Z. 2014. Climate-driven generation of a fluvial sheet sand-body at the Paleocene-Eocene            boundary in northwest Wyoming (U.S.A.). Basin Research 26: 225-241.

Foreman, B.Z., Clementz, M.T., Heller, P.L. 2013. Evaluation of paleoclimatic conditions east and west         of the southern Canadian Cordillera in the mid-late Paleocene using bulk organic d13C records.   Palaeogeography, Palaeoclimatology, Palaeoecology 376: 103-113.

Foreman, B.Z., Heller, P.L., Clementz, M.T. 2012. Fluvial response to abrupt global warming at the Palaeocene/Eocene boundary. Nature 491: 92-95.

Koch, P.L., Zachos, J.C., Gingerich, P.D. 1992. Correlation between isotope records in marine and    continental carbon reservoirs near the Palaeocene/Eocene boundary. Nature 358: 319-322.

Kraus, M.J., Riggins, S., 2007. Transient drying during the Paleocene–Eocene Thermal Maximum (PETM): analysis of paleosols in the Bighorn Basin, Wyoming. Palaeogeography, Palaeoclimatology, Palaeoecology, 245: 444-461.

Larson, T.E., Heikoop, J.M., Perkins, G., Chipera, S.J., Hess, M.A., 2008. Pretreatment technique for            siderite removal for organic carbon isotope and C:N ratio analysis in geological samples. Rapid     Communications in Mass Spectrometry 22, 865–872.

Lillegraven, J. A., Snoke, A. W., McKenna, M. C. 2004. Tectonic and paleogeographic implications of         late Laramide geologic history in the northeastern corner of Wyoming’s Hanna Basin: Rocky          Mountain Geology 39: 7-64.

Gill, J. R., Merewether, E. A., and Cobban, W. A., 1970, Stratigraphy and nomenclature of some Upper        Cretaceous and lower Tertiary rocks in south-central Wyoming: U.S. Geological Survey         Professional Paper 667: 53.

Magioncalda, R., Dupuis, C., Smith, T., Steurbaut, E., Gingerich, P.D. 2004. Paleocene-Eocene carbon         isotope excursion in organic carbon and pedogenic carbonate: Direct comparison          in a continental            stratigraphic section. Geology 32: 553–556.

Roberts, L.N.R., and Kirschbaum, M.A., 1995, Paleogeography of the Late Cretaceous of the Western Interior of middle North America—Coal distribution and sediment accumulation: U.S. Geological Survey Professional Paper 1561, 155 p.

Schmitz, B., Pujalte, V., 2007. Abrupt increase in seasonal extreme precipitation at the Paleocene-Eocene      boundary. Geology 35: 215–218.

Sewall, J.O., Sloan, L.C. 2006. Come a little bit closer: A high-resolution climate study of the early    Paleogene Laramide foreland. Geology 34: 81-84.

WOGCC , Wyoming Oil and Gas Conservation Commission well log database: (July 2016).

Wing, S.L., Currano, E.D., 2013. Plant response to a global greenhouse event 56 million years ago. Am.       J. Bot. 100: 1234–1254.

Wing, S.L., Harrington, G.J., Smith, F.A., Bloch, J.I., Boyer, D.M., Freeman, K.H., 2005. Transient floral     change and rapid global warming at the Paleocene-Eocene boundary. Science 310: 993–996.

Wroblewski, A. F.-J., 2003, The role of the Hanna Basin in revised paleogeographic reconstructions of the Western Interior Sea during the Cretaceous–Tertiary transition, in Horn, M. S., ed., Wyoming Geological Association Guidebook, 2002 Field Conference “Wyoming Basins” and 2003 Field Conference, p. 17–40.

Zachos, J.C., Pagani, M., Sloan, L., Thomas, E., Billups, K., 2001. Trends, rhythms, and aberrations in          global climate 65 Ma to present. Science 292: 6e6–693.

Using garnets to explore the beginning of subduction

Using garnets to explore the beginning of subduction

Using garnets to explore the beginning of subduction on Santa Catalina Island, California

Overview: In the late Cretaceous Period, before the San Andreas Fault started shearing off the edge of California, the geology of the Los Angeles region probably looked a lot more like the Pacific Northwest does now, with lines of volcanoes stretching all the way south from what is now Canada. These volcanoes were caused by the subduction of the Pacific Plate under North America. As the dense oceanic crust slid down into the mantle, it metamorphosed, growing new minerals and releasing water, which triggered melting, creating the arc of magmatism above. After subduction ended, more modern tectonic activity exhumed a remnant of the rocks that formed above the subducting plate, becoming Santa Catalina Island. Catalina has long been a laboratory for understanding the structure of subduction zones and how the fluids released during subduction change the composition of rocks. During the Catalina Gateway project, we will learn about the geochemistry of subduction zones, explore the island that has helped shape our understanding of how subduction works, and decipher the record of these chemical changes using the chemistry of the mineral garnet.

Geologists taking notes on Catalina Island

When: June 25 – July 27, 2018 (tentative)

Where: Oberlin, Ohio (introduction and lab work), Santa Catalina Island, California (field work), and Claremont, California (lab work)

Who: Nine students and project leaders Dr. Zeb Page (Oberlin College,, and Dr. Jade Star Lackey (Pomona College,

Prerequisites and Recommended Courses: Curiosity and excitement about our planet. Interest in learning how to use new tools from rock hammers to electron microscopes and mass spectrometers to figure out what was happening off the California coast 115 million years ago. Ability to work collaboratively with others. The rest we will learn as we go.

Expectations and Obligations:
1. Participation in all project-related work during the summer (June 25-July 27, 2018)
2. Commitment to work collaboratively in an environment of mutual respect.
3. Adherence to mutually agreed upon community standards of conduct we will collectively develop at the beginning of the project.


Franciscan-like subduction-related metamorphic rocks (blocks of garnet-bearing blueschist and amphibolite) were recognized on Catalina by the first half of the twentieth century (Woodford, 1924; Bailey, 1941). However, the modern era of Catalina geology began with detailed mapping and a tectonic model by Platt (1975). The metamorphic rocks of Santa Catalina Island (sometimes referred to as the Catalina Schist) consist of mappable units of dominantly metsedimentary rock that range from lawsonite-blueschist to amphibolite facies, with increasing grade correlated with structural height (Platt, 1975). Platt’s initial subdivision of the island into blueschist, greenschist, amphibolite, and ultramafic units bounded by shallow dipping thrust faults (Fig. 1) has been refined, with the “greenschist” unit now defined as epidote amphibolite and epidote blueschist overprinted with greenschist-facies assemblages (Grove and Bebout, 1995).

Figure 1: Geologic sketch map of Santa Catalina Island, California, modified from Platt (1975) and Grove and Barton (1995). The location of Catalina Island is shown in the red star on the inset map; the Franciscan Complex is shown in purple. The proposed study areas are shown in black rectangles.

The highest-grade amphibolite unit from Catalina records peak conditions of 7-12 kbar and 650-750 °C based on cation thermometry and fluid inclusion barometry (Platt, 1975; Sorensen and Barton, 1987). The unusually high temperatures and Barrovian-like assemblages of the highest-grade rocks became the basis for the interpretation that the Catalina Schist was formed in a nascent subduction zone. In this model, the amphibolite-facies rocks were formed at the initiation of subduction and recorded high temperatures due to proximity with the hot mantle wedge; the inverted metamorphic gradient of underthrust lower-grade units recorded the subsequent cooling of the trench (Platt, 1975; Cloos, 1985; Peacock, 1987). More recent analysis of detrital zircon ages from Catalina metasedimentary rocks has revealed that accretion of the Catalina Schist occurred over at least a 20 My period, with the lowest-grade units containing detrital zircons younger than the 115 Ma metamorphic age yielded by the high-grade rocks (Grove et al., 2008). Furthermore, a single garnet blueschist block (Fig. 2) found in the blueschist-facies mélange yielded high-error Rb-Sr and Ar-Ar ages of ~150 Ma suggesting that a pre-Catalina subduction zone existed in the region. The age of the garnet blueschist block was firmly established by a 155±8 U-Pb sphene age collected during the 2012 Keck project (Awalt et al., 2013). However, the P-T history of this key sample remains unconstrained, possibly due to multiple episodes of subduction as the Catalina trench become superimposed on the remnants of a thermally mature subduction zone through subduction erosion (Grove et al., 2008).

Figure 2: Tectonic block of garnet blueschist in a lawsonite blueschist mélange that may have experienced multiple episodes of subduction metamorphism.

Santa Catalina Island has long been used as a field laboratory to investigate devolatilization and fluid flow in subduction zones. Petrologic, geochemical, and chronological constraints on Santa Catalina Island have been used to document extensive fluid flow and metasomatism due to devolatilization of sediments during subduction (e.g., Sorensen and Grossman, 1989; Bebout, 1991; 2007; King et al., 2006, 2007). Many blocks in the amphibolite/ultramafic mélange have talc or tremolite metasomatic selvages or reaction rinds similar to those found in the Franciscan Complex. Unlike in the Franciscan, some of these selvages contain garnet that is compositionally different from that found in the blocks (Penniston-Dorland et al., 2013). In situ analysis of oxygen isotopes based on samples collected during the 2012 Keck Project has demonstrated that selvages contain garnet that grew both before and after rind formation (Leung et al., 2016). These garnets likely contain further information on the P-T history of rind formation and on the trace element composition of rind forming fluids.

As the scientific research component of the proposed gateway project, we will have students work collectively on three projects that will use in situ analysis of major and trace elements to address questions of tectonics (timing of garnet vs. lawsonite growth in garnet blueschist, trace element zoning in amphibolite garnets with variable inclusion populations) and metasomatism (major and trace elements in rind garnets). The specifics of these projects are detailed below.

As a Gateway project, we expect that students applying will only have 1-2 geology courses under their belt, so you can expect to learn the essential geology on as you go, and more importantly how to work with a team of other budding geoscientists. We’ll also give you insight into how the multitude of career prospects in Geosciences and pathways into them.

Active learning of foundational geology/geochemistry concepts

Students in the Gateway Project may come to the group with varying degrees of geology training, and we recognize that many may only have taken a single, introductory course (or may have had no geology at all). Furthermore, experience shows that many students come to geochemical research with uneven quantitative skills…perhaps most notably in the use of spreadsheets for calculations and data management. Thus, we plan to spend a substantial portion of the first 2.5 weeks of the program reviewing specific aspects of introductory geology and quantitative skills. We will do this through labs and field trips to local sites of interest. The five topics we intend to cover at a basic, introductory level are: geologic time, earth materials (with a specific focus on metamorphic rocks and their minerals) and plate tectonics. Obviously in just a few days at Oberlin we cannot cover these in great depth, but we can use these lab and field activities as inquiry based teaching to ensure a somewhat more level playing field for all the students. A typical morning in the first phase of the project might be spent doing the classic plate tectonics map jigsaw exercise, reviewing metamorphic minerals, or a field trip to a local river to brainstorm how one might measure discharge…followed by getting in and doing it. The afternoon would include time spent on the electron microscope analyzing traverses of zoned garnet by EDS, or calculating mineral formulae.

Potential Student Projects

            We propose three collaborative student research projects based on major and trace-element data from garnet and other minerals in Catalina blocks and rinds. Each project has some relatively straightforward hypotheses that are testable using the major and trace element data students will collect. This should ensure a relatively high likelihood of success for a meaningful conclusion of tectonic or metasomatic interest beyond simply descriptive work. The projects will have three phases: 1. At Oberlin: Introduction to SEM/EDS and data collection from existing samples from Catalina, begin GSA abstract(s) and poster(s). 2. On Catalina Island: A field component in which students will visit their sample sites, and perform a second phase of sampling guided by their lab work in phase one. Although this “inside-out” approach to geology research is not optimal, it seems the most efficient use of the five weeks available. 3. A final phase on campus at Pomona to collect trace element data by LA-ICPMS on targets previously characterized at Oberlin, to analyze selected “new” samples in quickly prepared thick sections and to obtain major and trace element compositions on these by X-ray fluorescence spectrometry while students finalize abstracts and print and present posters.

Relative timing of garnet and lawsonite growth in blueschist (3 students)

As described above, a large garnet, lawsonite blueschist block (Figure 2) with an anomalously old age is a key sample in understanding the tectonic history of Catalina. Preliminary attempts at thermodynamic modeling in order to reconstruct the pressure-temperature evolution of the rock did not succeed in reproducing the observed metamorphic assemblage. One possibility is that the garnet and dated sphene formed in an early metamorphism at 155Ma, and the lawsonite and glaucophane recrystallized in a second lawsonite-blueschist metamorphism after 115Ma. This is consistent with color zonation in glaucophane (Awalt et al., 2013). Students will collaborate on a detailed SEM/EDS petrography of the sample, including characterizing any chemical zoning in minerals. A first order question in the analysis of this rock is whether the garnet or lawsonite grew first, or if they grew in equilibrium. Work on the Lu-Hf geochronology of lawsonite has shown that both garnet and lawsonite strongly partition the Heavy Rare Earth Elements (HREE, Mulcahy et al., 2014)). Students will choose garnet and lawsonite targets while at Oberlin and analyze them for HREE at Pomona in order to address this issue, HREE depletion in either lawsonite or garnet is suggestive of growth in separate events.

A high-resolution garnet view of high-T metamorphism on Catalina (3 students)

Although most Catalina garnet-hornblende rocks contain <5mm diameter garnets, an unusual sample containing ~3cm garnets was collected during the 2012 Keck project. These garnets are chemically zoned, and contain ilmenite inclusions in their cores and rutile inclusions in their rims, demonstrating growth in an increasing pressure regime. Students will characterize the chemistry and identity of mineral inclusions in single large garnets and note correlations between changing garnet chemistry and inclusion populations. Depending on student interest and time constraints, students may apply quantitative thermobarometry to inclusion-garnet assemblages. At Pomona, students will look at correlations between trace elements and changing inclusion populations, as well as compare their results with those from other groups. They will also compare their results with the single existing published analysis of trace elements in Catalina (Sorenson and Grossman, 1989).

Comparing block and rind garnets (3 students)

Leung et al. (2016) documented three different generations of garnets in a single rind sample from one block (Fig. 3) on Catalina, first described by Penniston-Dorland et al., (2013). Three students will work collaboratively to describe the mineralogy of a block and two samples of garnet-bearing rind. They will compare major element chemistry and zoning patterns with those found in published works as well as the other group working on amphibolite garnet. They will determine if different populations of garnet that can be distinguished texturally and by oxygen isotope ratios have different trace-element patterns. they will also compare their results with Sorensen and Grossman (1989).

Figure 3: A garnet-hornblende tectonic block with garnet-bearing actinolite rind. Block core is exposed above chapstick tube (~5cm), rind below and to the right.


The first 2.5 weeks will be spent on campus at Oberlin College. During this time our objectives will include team building through introductory geology exercises and field trips with a focus on minerals and metamorphic rocks. We will dip our toes into the scientific literature and collect major element data on samples collected in 2012 on the SEM/EDS. The new Tescan-Oxford system at Oberlin can collect data in an automated fashion overnight, and students will spend time using the instrument in the afternoons and “data mining” maps collected overnight. As students develop an understanding of their projects and begin to collect data we will start to draft abstracts. We anticipate this will be a busy time, but will be sure to build in fun activities as well.

Page and the students will travel to Los Angeles together, meet Lackey at Pomona College to organize field equipment, and travel to Catalina en mass. The week on Catalina will start with field trips to get the lay of the land, and make observations of metamorphic rocks in the field. We will visit the outcrops that were sampled previously to talk about sampling strategy, and take a second round of samples informed by the observations already made by the students in the lab. Finally, there are several mélange units with blocks described in the Catalina literature of the 1970’s and 80’s (e.g., Pomona alumna Sorena Sorensen, 1986) that have not been worked on more recently, and we will take two days to do some reconnaissance work on the SW side of the island, in part to acquaint the students of how to approach a new field area (as opposed to a more guided field trip). The proposed field area is part of the 88% of Catalina Island that is privately owned and managed by the Catalina Island Conservancy. Private motor vehicles are not allowed, and all research must be permitted by the Conservancy. An extension of Page’s permit is straightforward to obtain, and we have already started this process. Last year the Conservancy provided camping and transportation support, and will again for this field season. Field equipment (Hammers, Bruntons, Trimble GeoXT handheld GPS receivers for detailed mapping) will be provided by Oberlin, and Pomona Colleges. As part of our orientation on the island, Conservancy staff will give us an overview of the important biological (a rare, undeveloped island ecosystem 25 miles from downtown LA) and cultural (>7000 years of pre-colonial habitation) aspects of Catalina. We will stress the importance of the permitting process and ethical behavior when sampling in culturally sensitive areas.

The final 1.5 weeks will be spent on campus at Pomona. There students will become familiarized with the LA-ICPMS system, including methods of standardization, instrument evaluation of data quality. They will analyze garnet and other minerals already identified at Oberlin, and reduce and correct trace element data using major element compositions already collected by SEM-EDS. Teams of students will rotate between ICP-MS work, preparation of XRF beads for whole rock chemistry, and interpretation of data. They will finish drafting abstracts and posters, and, we hope, have time for some local field trips, for example to the costal exposures of the San Onofre Breccia, which contains Catalina equivalent cobbles and gives to students a historical introduction of the discovery of subduction metamorphism as well as initiation of the San Andreas Fault system.


Conducting a research project at an early career stage is not only a résumé-builder, but helps to develop many skills that are applicable after the summer is over. Working and living together in the field, collaboratively completing a project from start to finish, and starting to develop a network of friends and colleagues all build resiliency, capabilities, and cognitive abilities.  This Gateway Keck project offers these experiences in a supportive yet challenging environment. Students will work on real scientific questions, using standard and state-of-the art field and lab equipment; they will also receive training in science communication, including informal interactions with the public in the field, and more formal methods of presenting information such as lightning talks and giving better, more engaging research presentations.


Awalt, M.B., Page, F.Z., Walsh, E.O., Kylander-Clark, A.R.C., and Wirth, K.R., 2013, New evidence for old subduction in the Catalina Schist, Santa Catalina Island, CA: Geological Society of America Abstracts with Programs, v. 45, p. 798.

Bailey, E.H., 1941, Mineralogy, petrology, and geology of Catalina Island, California: Ph.D. Thesis, Stanford University.

Bebout, G.E., 1991, Field-based evidence for devolatization in subduction zones; implications for arc magmatism: Science, v. 251, p. 413–416.

Bebout, G.E., 2007, Metamorphic chemical geodynamics of subduction zones: Earth and Planetary Science Letters, v. 260, no. 3-4, p. 373–393.

Cloos, M., 1985, Thermal Evolution of Convergent Plate Margins – Thermal Modeling and Reevaluation of Isotopic Ar-Ages for Blueschists in the Franciscan Complex of California: Tectonics, v. 4,  p. 421–433.

Grove, M., and Bebout, G., 1995, Cretaceous tectonic evolution of coastal southern California: Insights from the Catalina Schist: Tectonics, v. 14, p. 1290–1308.

Grove, M., Bebout, G.E., Jacobson, C., Barth, A., Kimbrough, D., King, R.L., Zou, H., Lovera, O., Mahoney, B., and Gehrels, G.E., 2008, The Catalina Schist: Evidence for middle Cretaceous subduction erosion of southwestern North America, in Formation and Applications of the Sedimentary Record in Arc Collision Zones: Geological Society of America Special Paper 436, p. 335–361.

King, R.L., Bebout, G.E., Moriguti, T., and Nakamura, E., 2006, Elemental mixing systematics and Sr-Nd isotope geochemistry of melange formation: Obstacles to identification of fluid sources to arc volcanics: Earth and Planetary Science Letters, v. 246, p. 288–304.

King, R.L., Bebout, G.E., Grove, M., Moriguti, T., and Nakamura, E., 2007, Boron and lead isotope signatures of subduction-zone melange formation: Hybridization and fractionation along the slab-mantle interface beneath volcanic arcs: Chemical Geology, v. 239, p. 305–322.

Leung, M.C., Page, F.Z., Penniston-Dorland, S.C., Kitajima, K., and Valley, J.W., 2016, Constraints on garnet-bearing metasomatic rind growth in subduction mélange through SIMS analysis of oxygen isotopes, in Geological Society of America, p. 281880–1.

Mulcahy, S.R., Vervoort, J., and Renne, P.R., 2014, Dating subduction-zone metamorphism with combined garnet and lawsonite Lu-Hf geochronology: Journal of Metamorphic Geology, v. 32, no. 5, p. 515–533, doi: 10.1111/jmg.12092.

Peacock, S., 1987, Creation and Preservation of Subduction-Related Inverted Metamorphic Gradients: Journal of Geophysical Research-Solid Earth and Planets, v. 92, p. 12763–12781.

Penniston-Dorland, S.C., Gorman, J.K., Bebout, G.E., Piccoli, P.M., and Walker, R.J., 2014, Reaction rind formation in the Catalina Schist: Deciphering a history of mechanical mixing and metasomatic alteration: Chemical Geology, v. 384, no. C, p. 47–61, doi: 10.1016/j.chemgeo.2014.06.024.

Platt, J.P., 1975, Metamorphic and deformational processes in the Franciscan Complex, California: some insights from the Catalina Schist terrane: Bulletin of the Geological Society of America, v. 86, p. 1337–1347.

Sorensen, S.S., 1986, Petrologic and geochemical comparison of the blueschist and greenschist units of the Catalina Schist Terrane, southern California, in Evans, B.W. and Brown, E.H. eds. Blueschists and Eclogites: Geological Society of America Memoir 164, Geological Society of America, p. 59–75.

Sorensen, S.S., and Grossman, J., 1989, Enrichment of trace elements in garnet amphibolites from a paleo-subduction zone: Catalina Schist, Southern California: Geochimica et Cosmochimica Acta, v. 53, p. 3155–3177.

Sorensen, S.S., and Barton, M., 1987, Metasomatism and Partial Melting in a Subduction Complex – Catalina Schist, Southern California: Geology, v. 15, p. 115–118.

Woodford, A.O., 1924, The Catalina metamorphic facies of the Franciscan Series: University of California Publications in Geological Sciences, v. 15, p. 49–68.

Paleoenvironmental analysis of ancient soil horizons

Paleoenvironmental analysis of ancient soil horizons

Paleoenvironmental analysis of ancient (petro)calcic soil horizons: disentangling climatic, geomorphic, and biological records in the Mojave Desert

Overview: This four-student project will test a suite of related hypotheses regarding the mineralogical, morphological, and geomorphic history of Mormon Mesa, NV, a 5-4 million year old Mojave Desert landform containing a complex carbonate-cemented (petrocalcic) soil profile. The Mormon Mesa soil serves as an important and fascinating analog for other calcic and petrocalcic soils around the world, as well as for paleosols in the stratigraphic record. This work will expand upon past research by using stable isotope geochemistry alongside detailed soil-stratigraphic and micromorphological descriptions to constrain the relative timing, climate context (e.g., pluvial versus interpluvial), formation history and durability of horizon components including laminae, concretions, and cemented matrix across the Mormon Mesa soil profile, and especially within its morphologically complex “massive” horizon (Brock and Buck, 2009). This project will produce the first stable isotope data from Mormon Mesa’s unique soil, and it will afford important, publishable new tests of closed-system assumptions for the use of isotope geochemistry and geochronology in (petro)calcic horizons and paleosols worldwide.

Sampling soil in the Mojave Desert

When: June 18-July 13, 2018

Where: Claremont, California (introduction and lab work) and Mormon Mesa, Nevada (field work)

Who: Four students and project leader Dr. Colin Robins (Claremont McKenna College,

Prerequisites and Recommended Courses: Suggested (but not required) are (1) a topical course from among Soil Science, Geomorphology or Quaternary Geology, and (2) core courses in the Geology major such as Mineralogy, Historical Geology, and Stratigraphy. Some background in chemistry is also recommended, whether through an Introductory Chemistry sequence or through a course such as Geochemistry, Environmental Chemistry, or Petrology. Applicants should have an interest in soil science and/or geomorphology, be willing to work in a few days of extreme heat, should also be interested in learning how to patiently master advanced laboratory analytical equipment. Preference will be given to students hoping to use this work for a senior thesis or capstone. Helpful, but not required in the letter of recommendation from the on-campus sponsor is an indication of the applicant’s ability to work independently. Also helpful for comment are the student’s propensity for careful description, attention to detail in laboratory work, and ability to hold up in trying field conditions.

Expectations and Obligations:

  1. Participation in all project-related work during the summer (June 18-July 13, 2018).
  2. Sample preparation, analytical work, and interpretation with a research advisor at the student’s home college
  3. Co-author an abstract and (co-)present a poster for the Geological Society of America Meetings in Indianapolis, IN, November 4-7, 2018.
  4. Write a short contribution (4-6 pages text + figures) to be published in the Proceedings of the Keck Geology Consortium 2019 Volume (first draft due Mid-February).
  5. Expected but not required: Use this work for the completion of a senior thesis (or equivalent) at your home institution. Potentially help convert the study into a manuscript for peer-reviewed journal publication down the road.


Geologic Overview Soils are fascinating geological features that reflect the complicated dynamics of climate, organisms, Earth materials, and surface processes over long (103 to 106) time spans. In deserts especially, small magnitude precipitation or temperature shifts can impart large magnitude responses in soil chemistry, mineralogy, and profile morphology (Chadwick and Chorover, 2001). Soils and regolith developed in humid climates largely reflect the hydrolysis of primary minerals and the loss of soluble cations from the Earth’s surface, but arid soil profiles instead reflect a net gain of ions via dust and rainfall over time (Gile et al., 1981). Combined with strong alkalinity and high potential evapotranspiration, this solute influx yields a diversity of environmentally sensitive, pedogenic mineral assemblages including carbonates, sulfates, nitrates, and chlorides, and phyllosilicates such as smectite, palygorskite, and sepiolite (Dixon and Weed, 1989; Brady & Weil, 2008; Graham et al., 2008; Brock-Hon et al., 2012; Robins et al., 2012). Each of these minerals, some quite rare, serves as a marker of its own narrow range of soil chemical conditions. Tantalizingly, invaluable paleoenvironmental data may therefore be coded into the isotopic or elemental geochemistry of each pedogenic mineral. Vexingly, this authigenic record can be easily biased or erased by subsequent cycles of soluble mineral dissolution and recrystallization, or even skewed by unrecognized lithogenic contamination (Brock and Buck, 2005; Kraimer and Monger, 2009; Robins et al., 2014). Careful work is sorely needed to identify and to model the linkages between geochemistry, mineralogy, profile morphology, and regional geomorphology before conducting meaningful isotopic analysis of arid soil/paleosol minerals. Given predicted climate change trends, it is imperative to better constrain rates of soil geomorphic processes in arid and semi-arid landscapes, which comprise a third of Earth’s terrestrial environments and marginally support up to two billion people. Soils and paleosols characterized by pedogenic carbonate (mainly calcite and low-Mg calcite) accumulation are perfect subjects for such research. Carbonate-cemented soil horizons cap geomorphic surfaces in modern, arid to semi-arid landscapes worldwide, and they also mark unconformities in the stratigraphic record (e.g., Reeves, 1976; Machette, 1985; Retallack, 2001). Under steady environmental conditions, pedogenesis drives progressive morphological evolution of the soil from soft calcic horizons (stage I & II) to hard petrocalcic horizons (indurated, stage III-VI; sometimes informally called “calcrete” or “caliche”) driving positive feedbacks with landscape hydrology (Gile et al., 1966; Bachman and Machette, 1977; Machette, 1985). Rates of carbonate pedogenesis vary widely with climate and parent material; calcic horizons can prove more complex than assumed. Precise, local models are needed on a site-by-site basis to link mineralogical and soil structural (micromorphological) evolution to regional geomorphic histories (e.g., Alonso-Zarza et al., 2002; Brock and Buck, 2009). Critically, isotopic data can and must be used to validate site-specific models. Isotopic analysis of pedogenic CaCO313C and δ18O), phyllosilicates (δ18O) , and barite (δ34S and δ18O) from different soil developmental stages can yield useful insights into paleovegetation (e.g., Deutz et al., 2001), paleotemperature (Quade et al., 2013), microbial activity (e.g., Jennings and Driese, 2014), and more.

Figure 1: Location of the Mormon Mesa soil geomorphic surface (Soil Survey Staff, 2006) in southern Nevada. Proposed sample locations include (A) Riverside, (B) Halfway Canyon, and (C) Logandale. Basemap data modified from USGS (2005).

Mormon Mesa, Nevada (Fig. 1) hosts perhaps the oldest, extant petrocalcic soil profile in North America. The landform poses a rich set of questions for paleoenvironmental and geochronologic research. Due to its extreme age and relatively restricted spatial extent, Mormon Mesa is even a possible candidate for rare/endangered soil classification. Mormon Mesa’s sequence of three to four petrocalcic (Bkkm) horizons caps sediments of the Miocene-Pliocene Muddy Creek Formation (MCF) (Fig.2) (Gardner, 1972; Brock and Buck, 2009). Within the soil, pedogenic laminae, pisoliths (e.g., irregular, > 2mm concretions indicative of rotation), dissolution voids and other features (Fig. 3) reflect episodes of calcite precipitation, horizon brecciation, and re- cementation (Brock and Buck, 2009). MCF deposits are fluvial and eolian sediments deposited in a closed basin prior to incision of the Virgin River upon interception by the lower Colorado River (Kowallis and Everett, 1986; Williams et al., 1997). The uppermost MCF strata exhibit pedogenic carbonate nodules (stage II calcic horizon). Onset of pedogenesis at Mormon Mesa is thus considered synchronous with incision of the lower Colorado River system ~5.6 – 4.2 Ma (Faulds et al., 2002; House et al., 2005). A 5-4 Ma age for the Mormon Mesa surface is further supported by regional stratigraphic and morphostratigraphic correlation with isotopically dated tuffs and basalts (Schmidt et al., 1996; Williams et al., 1997; Faulds et al., 2002). Incision produced ~200 m of relief between the mesa’s surface and the modern floodplain (Fig. 2). Combined with an overall arid to semi-arid climate history, incision is hypothesized to have stopped interaction of the soil with groundwater, however, stable isotope data are needed to confirm this long-standing assumption. The Mormon Mesa soil has been previously described and variably interpreted (Gardner, 1972; Bachman and Machette, 1977; Soil Survey Staff, 2006). Its current soil geomorphic model was developed by Brock and Buck (2009), and models for its mineral evolution (Robins et al., 2012) and the genesis of its pedogenic ooids (Robins et al., 2015) have been recently published as well. Nonetheless, the polygenetic nature of this soil and the complexity of its micro-morphological and mineralogical architecture warrant further study, especially regarding the relative timing of authigenic mineral crystallization. None of the published models have ever been validated with stable isotope data. Detailed elemental geochemical comparisons have not been made for individual minerals between horizons nor between micromorphological features (e.g., laminae, pisoliths, matrix, dissolution voids). Finally, the potential of the soil for geochronology appears low (e.g., Robins et al., 2014) but has not yet been fully evaluated. Importantly, models developed at Mormon Mesa may be cautiously applied to many other calcic and petrocalcic horizons and paleosols worldwide.

Figure 2(A): Mormon Mesa soil-geomorphic surface (view from “Riverside” site, looking to the northeast), with white petrocalcic (calcrete) horizons capping red sediments of the Muddy Creek Formation (MCF); ~200 vertical meters separate the top of Mormon Mesa from the Virgin River channel, right (southeast). (B): Mormon Mesa soil profile at “Riverside” site, showing the “Brecciated” (surface) horizon atop the “Massive” stage VI petrocalcic and “Transitional” stage III horizons (transitional to stage II MCF paleosols). Horizon nomenclature from Brock & Buck (2009).

Figure 3(A): Polished sample of the Massive horizon (“Riverside” site); evident micromorphological features include laminae (L), brecciated laminar fragments (LF), pisoliths (P), and undifferentiated carbonate-cemented matrix (M). Each feature class may yield distinct isotopic signatures (Image from Robins et al., 2015). (B): Large dissolution pipe (D) in the massive horizon at the “Logandale” site.

Goals and Significance of the Project Isotopic analyses of calcic and petrocalcic soils are increasingly being used for geochronology and/or paleoenvironmental reconstruction (temperature, precipitation, vegetation), however, the suitability of discrete mineral and micromorphological components for these analyses is not guaranteed, needs to be evaluated on a case-by-case basis, and bears more detailed consideration overall. The goal of this project is to use stratigraphy, geomorphology, (micro)morphology, mineralogy, and geochemistry as corroborative data sets with which to test a suite of related hypotheses regarding the relative age and closed-system behavior of calcic soil minerals and micromorphological components (laminae, matrix, ooids). This work is significant and needed to expand and to refine our understanding of arid soil pedogenesis (past, present, and future) and the response of arid soil landforms to environmental change. Four related but independent student projects will be chosen by Dr. Robins and the students from among the options below.

Potential Student Projects

  • Dissolution Characterization (1-2 students): Dissolution pits, pipes, and extensive fractures scar the horizons of Mormon Mesa and other late-stage carbonate soils. Some features are joint-like, anecdotally thought to be formed by earthquakes and then enhanced by rooting and infiltration. The origin of others is less clear. Importantly, dissolution represents corruption or isotopic resetting of CaCO3 and it is the primary reason why numerical dates for petrocalcic horizons remain problematic. A project to describe, measure , and define dissolution features, and to distinguish dissolution under subaerial conditions from dissolution within-profile would be impactful for an international community of researchers. Such work entails: (1) profile description at the Riverside and Logandale sites (Figure 1), and description of case hardening at Halfway Canyon (an active arroyo with groundwater calcrete), accompanied by concurrent, new (2) sampling of (a) surface clasts, (b) rinds along dissolution zones within the massive horizon, and (c) groundwater calcrete, (3) micromorphological description of clasts and dissolution rinds via (a) optical microscopy and (b) SEM-EDS (for microkarst), and (4) δ13C and δ18O from transects across clasts (2 per site) and rinds (2 per site). This project could dovetail with clay mineral research(below) as pedogenic clays may coat pit bottoms after carbonate dissolution.
  • Phyllosilicate Mineralogy (1 student): Palygorskite and sepiolite are fibrous, Mg-phyllosilicates formed in calcic and petrocalcic horizons via chemical solution feedbacks with calcite, silica, and barite, (Robins et al., 2012). Elements to build these clays are supplied by force of crystallization dissolution of primary silicates by calcite (Watts, 1980; Robins et al., 2012), and by alteration of lithogenic illite or smectite. Palygorskite and sepiolite pervade Mormon Mesa’s horizons, however, some features contain a greater abundance of them than others. Importantly, the lattice structure of palygorskite and sepiolite may provide long-term microporosity to explain the measurable water holding capacity of petrocalcic horizons (Duniway et al., 2007). A study is needed to (1) quantify palygorskite/sepiolite abundance and (2) assess their geochemical variability across the full soil-stratigraphic section from MCF sediments up through surface eolian sands. Separating clays from indurated, calcite overgrowths is time-consuming, but the student would begin with isotopic, XRD, and geochemical analysis of archived samples, then tackle samples from the MCF, transitional and surface horizons while dissolving samples of the massive and brecciated horizons. Analysis of δ18O in clays from each micromorphological feature type would help definitively assign climate context to those features.
  • Differentiation of Matrix, Pisoliths, and Laminae (1-2 students): Beginning perhaps by 5 Ma, and certainly by the Pleistocene, weakly cemented ancestral calcic horizons containing nodules, clast pendants, calcified fungal filaments or rhizo-concretions, and strongly indurated ancestral petrocalcic horizons containing massively indurated matrix, laminae, and concretions were partially or completely eroded and redeposited by flash floods reworking the Mormon Mesa surface. Fluvial and/or eolian sands reburied these fragments, which were then re-cemented by subsequent pedogenesis. Thus, Mormon Mesa’s horizons are a kind of pedogenic conglomerate in which clasts are fragments of widely varied calcic horizon stages and ages. Research is needed to: (1) describe the type and spatial context of fragments throughout the soil profile, (2) measure the relative abundance of detrital silicates and pedogenic calcite, sepiolite/palygorskite, barite, and amorphous silica in distinct components of each horizon, and (3) determine whether calcite in each feature records distinct or similar isotopic signatures, to test existing models (Brock and Buck, 2009).
  • Barite neoformation (1 student): Barite is generally considered insoluble in alkaline soils (Lynn et al., 1971; Kabata-Pendias, 2011), yet authigenic barite has formed in the Mormon Mesa massive horizon (Brock et al., 2012). Barite’s solubility can double with each tenfold increase in ionic strength from Na and Cl (e.g., Stoops and Zavaleta, 1978; Blount, 1977; Sullivan and Koppi, 1993; Hanor, 2000), and Mg also increases Ba solubility in alkaline pH. Thus, Mg depletion from soil solutions during sepiolite or palygorskite crystallization under slightly saline interpluvial climates could drive barite precipitation, explaining the close spatial association between barite and these clays (Brock-Hon et al., 2012). Thus, barite may be an important marker of soil chemical and hydrological processes and it may eventually prove common in many other old, extant petrocalcic soils around the world. An project on this topic will employ δ18O and δ34S analysis of barite separates to test hypotheses regarding: (1) Ba mobilization during drier, interpluvial climates when solutions are more saline, and (2) the role of microbial processes in supplying sulfate for mineralization (Brock-Hon et al., 2012). Alternatively, (3) hollandite, a Ba-Mn oxide found in desert varnish and dust throughout the U.S. Southwest could be investigated as a hypothesized source for Mormon Mesa’s Ba. Hollandite could be sought in the eolian sand dunes and ramps on and surrounding Mormon Mesa. Ba, Mn, Mg, and Na relationships could be tested via soluble element analysis across the soil profile.
  • Pedogenic Ooids (1 student): Pedogenic ooids have been documented in the Mormon Mesa soil, and they are known from other calcic soils (Bachman & Machette, 1977). This project would be designed to test models of ooid genesis (Robins et al., 2015) against their occurrences in and absences from specific soil horizons and micromorphological features. This project would improve models of soil profile development and help constrain the relative timing of specific pedogenic processes.

Figure 4.


Overview: Figure 4 lays out a rough timeline for the first four weeks of the project. Students will meet in Claremont for a few days of orientation, geological background, soil science training, and project discussion before we drive to field sites for soil-stratigraphic description and sampling at Mormon Mesa. We will return to Claremont to prep samples for analysis (on campus, back at the students’ home campuses, as well as at external laboratories), to train on analytical equipment, and to refine hypotheses based on field observations and preliminary analysis. Students will complete their project and their literature review at their home institutions.

Field Work: Students must be willing to start field work at first light, eat in the heat, get to bed early and responsibly, and to endure several days of significant heat (90 – 115°F) while remaining on task with detailed soil-stratigraphic description, sketching, photographing, and sampling. Long sleeved light-weight clothing (zip-off pant legs are ideal) and a desert-appropriate hat are mandatory.

Analytical Work: Students will train in Claremont in order to be able to independently complete laboratory data collection and interpretation at their home institution according to expectations and established soil science method protocols. Some samples will be prepped for isotopic analysis by external laboratories, though students will be exposed to stable isotope analytical methods at Pomona College. Training will include exposure to rock crushing and grinding equipment, an XRF spectrometer, an XRD spectrometer, a field-emission SEM, an ICP-OES, and a new stable isotope mass spectrometry laboratory.

SAFETY ISSUES Vehicle travel along the L.A.-Las Vegas I-15 corridor poses the single greatest risk in this project. All effort will be made to avoid northbound travel on Fridays, and southbound travel late on Sundays, when traffic is at its worst. Summer temperatures in the Mojave Desert are extreme, often exceeding 110°F. Even brief visits to remote field sites short distances from well-maintained air-conditioned vehicles in June/July can prove draining, especially when sampling or describing profiles. By starting promptly at sunrise and ending by 2pm, and with a short number of successive days in heat, we can safely achieve the objectives of profile description, stratigraphic description, photography, and sampling. All sample sites in this project are on Bureau of Land Management parcels in existing road or wash cuts, and a permit request for June 2018 sampling has already been submitted and is pending now. Sampling requires a gas-powered concrete-cutting chain saw (e.g., a “quickie” saw commonly used in construction). With proper use, maintenance, and all due safety precautions (e.g., personal protective gear including hard hat, face shield, and safety glasses) the likelihood of accidents is low, however, some risk is inherent whenever using power tools. Students will train on the saw in Claremont prior to fieldwork; they must be comfortable lifting 50 pounds to do so. Rattlesnakes are a risk, but sampling noise usually scares wildlife away. In Claremont, all students are required to attend chemical safety and fire extinguisher training sessions (free) before starting lab work in the W.M. Keck Science Department.


Students will be expected to co-author at least one collaborative poster on mineralogy, micromorphology, and soil-geomorphic evolution of the Mormon Mesa petrocalcic soil for the Geological Society of America meetings in Indianapolis, IN, November 4-7, 2018. GSA 2018 is a perfect early target date for students to summarize their individual and group research efforts, and this project will support student travel, registration, and lodging for attendance and presentation at the GSA meetings. Excitingly, the relatively young GSA Soils and Soil Processes Working Group (new title forthcoming) is becoming permanently established and provides a nice network for student learning. All students are required to complete a 4-6 page paper (short contribution) that will be published in the Proceedings of the Keck Geology Consortium 2019 Volume (see examples from previous years). The first draft of this paper will be reviewed by your research advisor at your home institution sometime in late February, 2019, with the revised version sent to the project directors by March 1. Final versions of your paper and figures will be submitted to the Keck Office in Mid-March.


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Bachman, G.O., and M.N. Machette. 1977. Calcic soils and calcretes in the southwestern United States. U.S. Geological Survey Open File Report 77-794. U.S. Gov. Print. Office, Washington, DC.

Blount, C.W., 1977. Barite solubilities and thermodynamic quantities up to 300°C and 1400 bars. American Mineralogist, 62: 942-957. Brady, N.C. and Weil, R.R., 2008. The nature and properties of soils, fourteenth edition (revised). Pearson Prentice Hall, Upper Saddle River.

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Dixon, J.B., and S.B. Weed, editors. 1989. Minerals in soil environments, 2nd edition. SSSA Book Series 1. Soil Science Society of America, Madison, WI.

Duniway, M.C., Herrick, J.E. and Monger, H.C., 2007. The high water-holding capacity of petrocalcic horizons. Soil Science Society of America Journal, 71(3): 812-819.

Faulds, J.E., L.A. Gonzalez, M.E. Perkins, P.K. House, P.A. Pearthree, S.B. Castor, and P.J. Patchett. 2002. Late Miocene-Early Pliocene transition from lacustrine to fluvial deposition: inception of the lower Colorado River in southern Nevada and northwest Arizona. Geol. Soc. Am. Abst. Prog. 34(4):60.

Gardner, L.R., 1972. Origin of the Mormon Mesa Caliche, Clark County, Nevada. Geological Society of America Bulletin, 83: 143-156.

Gile, L.H., Hawley, J.W. and Grossman, R.B., 1981. Soils and geomorphology in the Basin and Range area of Southern New Mexico – Guidebook to the Desert Project. New Mexico Bureau of Mines & Mineral Resources, Memoir 39. University of New Mexico, Socorro, 222 pp.

Graham, R.C., Hirmas, D.R., Wood, Y.A. and Amrhein, C., 2008. Large near-surface nitrate pools in soils capped by desert pavement in the Mojave Desert, California. Geology, 36(3): 259-262.

Hanor, J.S., 2000. Barite-celestine geochemistry and environments of formation. In: C.N. Alpers, J.L. Jambor and D.K. Nordstrom (Editors), Sulfate minerals: crystallography, geochemistry, and environmental significance. Reviews in Mineralogy and Geochemistry. The Mineralogical Society of America, Washington, pp. 192-275.

House, P.K., Pearthree, P.A., Howard, K.A., Bel, J.W., Perkins, M.E., Brock, A.L., 2005. Birth of the lower Colorado River – Stratigraphic and geomorphic evidence for its inception near the conjunction of Nevada, Arizona, and California, in: Pederson, J., Dehler, C.M., eds., Interior Western United States: Boulder Colorado, Geological Society of America Field Guide 6. Geological Society of America, Boulder.

Jennings, D.S. and Driese, S.G., 2014. Understanding barite and gypsum precipitation in upland acid-sulfate soils: An example from a Lufkin Series toposequence, south-central Texas, USA. Sedimentary Geology, 299: 106-118.

Kabata-Pendias, A., 2011. Trace elements in soils and plants, fourth edition. CRC Press, Boca Raton, FL, 505 pages pp. Kowallis, B.J., and B.H. Everett. 1986. Sedimentary environments of the Muddy Creek Formation near Mesquite, Nevada. Sed. Assoc. Pub. 15:69-75.

Kraimer, R.A. and Monger, H.C., 2009. Carbon isotopic subsets of soil carbonate – A particle size comparison of limestone and igneous parent materials. Geoderma, 150: 1-9.

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Reeves, C.C., Jr., 1976. Caliche: origin, classification, morphology and uses. Estacado Books, Lubbock, 233 pp. Retallack, G.J., 2001. Soils of the past: An introduction to paleopedology. Blackwell Science, Malden, MA, 404 pp.

Robins, C.R., Brock-Hon, A.L. and Buck, B.J., 2012. Conceptual mineral genesis models for calcic pendants and petrocalcic horizons, Nevada. Soil Science Society of America Journal, 76(5).

Robins, C.R., Buck, B.J., Spell, T.L., Soukup, D.A. and Steinberg, S.M., 2014. Testing the applicability of vacuum-encapsulated 40Ar/39Ar geochronology to pedogenic palygorskite and sepiolite. Quaternary Geochronology, 20: 8-22.

Robins, C.R., Deurlington, A., Buck, B.J. and Brock-Hon, A.L., 2015. Micromorphology and formation of pedogenic ooids in calcic soils and petrocalcic horizons. Geoderma, 251-252: 10-23.

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Landscape and environmental change in Glacier National Park

Landscape and environmental change in Glacier National Park

Landscape and environmental change in Glacier National Park, Montana

Overview: This eight-student project uses sediment core samples to reconstruct glacial history, Holocene climate, and human impacts to Glacier National Park, Montana (GNP). Chains of lakes in glacial valleys collect the sediment produced by the glaciers and surrounding landscapes, providing a detailed record of glacier advance and retreat, climate, ecology, geomorphology, and land use change from the Pleistocene through the Anthropocene. Building on previous Keck student projects in 2010 and 2014, and coring/sampling in new sites, students will use mineralogy to reconstruct glacier size, organic carbon to investigate human impacts, microscopic charcoal fragments to build a record of past wildfire frequency, and multisensor instrumentation to discern geochemical differences between lakes with differing degrees of human impact. The group will have the opportunity to talk about their research with Park staff and the public.

Geologists hiking through the high country of Glacier National Park

When: July 8 – August 11, 2018 (tentative)

Where: St. Paul/Minneapolis, Minnesota (introduction and lab work) and Glacier National Park, Montana (field work)

Who: Eight students and project leaders Dr. Kelly MacGregor (Macalester College,, and Dr. Amy Myrbo (LacCore/CSDCO, University of Minnesota,

Prerequisites and Recommended Courses: Because this experience is targeted for students early in their academic careers, there are no specific coursework prerequisites. We are seeking students who are interested in many or all of the following: limnology, geomorphology, glaciers, wildfires, human impacts to lake ecosystems, natural and manmade climate change, erosion and sedimentation, and using field and laboratory methods to explore scientific questions about Earth surface processes.

Ideally, students will have some comfort with (or willingness to experience!) sharing close quarters in tents in cold and sometimes rainy weather, boating and swimming, communicating with the public and tourists ‘on the spot,’ hiking up to 12 miles in a day (typically 4-5 miles a day), and being without cell phone coverage for up to a week.  Students will need to maintain composure in field conditions that are safe but that may include bad weather, difficult trail and boat conditions, and wildlife (including bears). Support in the form of field gear loans will be provided to students who do not own their own. All tents and cooking gear will be provided.

Expectations and Obligations:
1. Participation in all project-related work during the summer (approximately July 8-August 11, 2018)
2. Write a team abstract and present a paper (poster or talk) at the Geological Society of America National Meeting in Indianapolis, IN November 4-7, 2018 (all expenses covered).


This project utilizes the remote and relatively pristine landscape of Glacier National Park, Montana as a natural laboratory for understanding the impacts of climate change on alpine landscapes, both natural (e.g., glacial-interglacial cycles, Little Ice Age) and anthropogenic. Understanding controls on past climate variability is key to assessing potential future environmental change. The climate history of the northern Rocky Mountains is known primarily from lacustrine paleoecological records that are widely spaced in Montana, Idaho, and Wyoming (e.g., Karsian, 1995; Doerner and Carrara, 1999; Millspaugh et al., 2000; Doerner and Carrara, 2001; Brunelle and Whitlock, 2003; Hofmann et al., 2006; Shapley et al., 2009). In 2005, 2010, and 2014, we collected lake cores in Swiftcurrent Lake, Lake Josephine, and lower Grinnell Lake, all of which are located downstream of Grinnell Glacier in the Many Glacier region of Glacier National Park, Montana (Figure 1).  Work done on these cores by previous students (many of them as part of Keck projects) has provided additional constraints on climate and environmental history in the basin since the end of the Last Glacial Maximum.  For example, a continuous core from Swiftcurrent Lake spanning ~17,000 years demonstrates a strong link between climate in the basin and solar forcing on centennial timescales (MacGregor et al., 2011), as well as links between glacier size and detrital dolomite in the lakes (Schachtman et al., 2015). A manuscript in preparation (including two Keck students as co-authors) explores the fire history of the region during the Holocene and demonstrates a link between fire frequency and increased geomorphic activity on the surrounding hillslopes. Another manuscript examines changes in the carbon signatures in lake sediment as a result of human activities in the Park over ~150 years.

Figure 1.

This year, our project will focus on the collection of short lake core transects (top ~50 cm of sediment at the lake bed) in a suite of lakes in the Many Glacier and Swiftcurrent valleys to understand environmental and landscape change over the past several centuries. These cores will allow us to: 1) provide enhanced spatial resolution of dolomite transport in the proglacial hydrologic system to enhance our understanding of the relationship between hillslope processes, glacial erosion, and lake transport and sedimentation; 2) measure the presence and concentration of charcoal in the lakes as a result of forest fires from summer 2017 and 2015 and compare the severity to Holocene fires; 3) assess the human impacts on the watershed through collection and dating of near-surface sediments; and 4) understand the hydrologic and sedimentologic transport of basin sediment in two contrasting geomorphic valley systems (one with deep glacial lakes and the other with primarily shallow paternoster lakes). We also plan to collect basic lake chemistry data to examine modern environmental conditions in the lakes.

There is broad interest in the future of our National Park system, as well as the response of glaciers to climate change.  Visitation in National Parks continues to grow each year, with record numbers in 2017 ( Glacier National Park is sensitive to climate change through glacial retreat (e.g., Key et al., 2002) and ecosystem adjustments (e.g., Klasner and Fagre, 2002), and there is widespread interest in the effects of future climate change in this unique and public space. This research project is aimed at understanding environmental and climate change in a near-pristine alpine basin in North America and will collect data relevant to the debate about the impacts of humans on remote landscapes. The research has relevance to communities in geomorphology, Quaternary geology, glaciology, and paleoclimatology, as well as to the general public interested in the impacts of climate change.

Study Area

The Many Glacier region of Glacier National Park in northwestern Montana has been our research site for the past 14 years. For the 2018 field season we will add the Swiftcurrent Valley and its lakes to our ongoing research area of the adjacent Grinnell Valley.  Glaciers that have diminished significantly since the 19th century occupy the heads of both of these valleys.

Goals and Significance of the Project

  1. Students will gain foundational knowledge of a) formation of sedimentary and intrusive igneous rocks, b) regional metamorphism and mountain building, c) climate variability during the Pleistocene, d) glacier dynamics and subglacial/supraglacial erosion, and e) sediment transport and deposition in glacial lake systems.
  2. Students will learn to read and interpret topographic and geologic maps, including locating themselves in the field.
  3. Students will learn to make measurements of active processes and collect samples with an understanding of WHY the data/results are important/interesting.
  4. Students will learn how to explain the relevance of their research project to a variety of people (peers in the field, Park visitors, Park Rangers, peers at the national GSA meeting, users of the Flyover Country mobile app for geoscience).
  5. Students will be able to identify ways in which their own life affects (and is affected by) interactions with the Earth (Fink, 2003).
  6. Students will learn how to be an effective team member in the context of both the field and the laboratory.
  7. Students will learn about the scientific process, including the role of problem-solving, creativity, quantitative reasoning, and revision in science.
  8. Students will gain confidence in their abilities as a scientist, including working in the field and the lab.

Potential Student Projects

In summer 2018, we envision a wide range of possible student projects.  We plan to have the students work on projects in pairs based on their interests.  We also recognize that there are situations that can alter research plans (i.e., weather, trail closures due to bears, forest fires, equipment malfunction, etc.), and we have ‘backup’ projects based on sediment cores we have already collected.

  • Detrital minerals as a proxy for glacier size: Previous work suggests dolomite (present only beneath Grinnell Glacier and along the Continental Divide) can be used as a proxy for glacier size (MacGregor et al., 2011; Schachtman et al., 2015).  However, we do not fully understand the role that upstream lakes may play in filtering dolomite along its transport path.  A detailed analysis of dolomite presence over time in a downstream transect of gravity cores (the top ~20-70 cm of sediment) in both the Grinnell Glacier and adjacent Swiftcurrent valleys would provide important details about dolomite transport and deposition.  In addition, the grain size of dolomite as compared to the quartz and chlorite/illite fraction in the sediments needs to be investigated to model grain transport. This could be investigated through smear slide analysis, loss on ignition (LOI), color analysis of the core scans, and XRD as part of several projects.
  • In addition to examining detrital minerals, students can conduct LOI measurements to determine the organic carbon fraction of lake sediments. Comparing LOI at two sites, or along a valley transect, can provide data that reflect the amount of organic carbon inputs into the lakes and how that varies in space and time. This speaks to both modern climate change and possibly human impacts on the Park landscape.
  • Fire history & modern fire records: Large fires occurred within the Park boundary in 2015 and again in 2017. With permission from the Park, we would like to sample from a lake more proximal to the 2017 Sprague fire (Lake Ellen Wilson or Avalanche Lake); surface cores collected from the two valleys in Many Glacier are also likely to produce records of fires in the past several hundred years.  Transects of charcoal records could illuminate transport of charcoal particles in high-relief alpine systems, which has not been the focus of previous research. If there is interest, we may try to search for microplastic spherules in the lake sediments as markers of the Anthropocene.
  • Timing of fires: We propose to collect ~4 new 19th-21st century cores to provide high resolution age control and to allow for detailed analyses of the historic time period in this lake. Students could compare sedimentation rates and patterns higher up in the Grinnell/Swiftcurrent valleys.
  • Modern lake processes: portable hydrolabs can measure dissolved oxygen, pH, turbidity, conductivity, temperature, and other metrics.  Comparisons between glacier-fed and unglaciated lakes could be made, as well as comparisons of human-proximal and human-distal regions of the valley. In addition, they can make comparisons between measurables in GNP lakes and those in other alpine systems affected by climate change (e.g., Fink et al., 2016).

Figure 2.


Our tentative dates are July 8-August 11, 2018.

We will meet in Minneapolis/St. Paul and spend 5-6 days at the dorms at Macalester College for classroom and laboratory ‘crash courses’ to prepare for the field work and research projects.  This will include mini-lectures, hands-on activities, talks by faculty and researchers in the geosciences at the U of M and Macalester, and training at LacCore. Material presented will bring all students up to speed on the geoscience background for the project, including the geologic evolution of the Park, global climate change, and surface processes.  While many of these topics will be introduced during the beginning of the project, we expect this learning will continue during our travel and in the field.

We will spend two days driving to Many Glacier (camping on the way), where we will set up camp. We plan to cook most meals in the campground during our ~12-14 days camping.  The first several days in the field will be spent giving the group an overview of the geology, biology, and history of the Park, as well as reading about use conflicts between the Park and the Blackfoot Indian community in the region.  The group will watch a training video on bear safety at the Many Glacier Ranger Station and learn to safely hike and camp in the Park. We plan to travel and hike (up to 12 miles/day) in other parts of the Park, including Logan Pass (continental divide) and West Glacier (near the major 2017 fires).  Collection of lake cores, water sampling, and any additional mapping/sampling will be conducted in small groups over the course of 5-7 days.  As we have done each summer working in the Park, the group will present our past findings and current projects to the Park Rangers during our stay. We also anticipate daily interactions between students and the public.

After returning to the Twin Cities, students and peer mentors will again stay at Macalester and drive daily to LacCore, where they will split, log, photograph, and describe the cores in accordance with standard limnogeological community procedures. Core description will provide much of the needed basis for answering research questions; students will collect samples and begin to conduct analyses for their projects.  During this time, the group will shop and cook dinners together, independent of the project leaders but with the help of a peer mentor.


MacGregor and Myrbo are experienced field scientists with experience in similar landscapes across the globe. They are familiar with safety issues specifically related to bears, alpine weather conditions, and boating.  There is little question that there are a host of inherent risks in this proposed work, but we will try to minimize this risk through training, communication, assessment of student abilities, and planning.  Here we briefly address the most common concerns.

Bears: We will spend the bulk of our field time camping in bear country, with large populations of both black and grizzly bears. Students will be trained by Park rangers in proper food storage and camping/hiking safety.  Each team of students/researchers will carry pepper spray and travel in groups of 4-5 for the majority of the field work. Note that past projects have all encountered bears at a safe distance, as well as sightings of moose and even wolverines.

Boats:  To collect samples of sediment and other physical measurements of lake water, we will be using non-motorized inflatable boats, including kayaks.  Students are required to wear life jackets at all times, and the lakes are small enough in size that the shorelines are always visible. Students will always boat with at least one other person, with clear communication about the planned route and expected time on the water.

Weather/conditions:  The weather in the Park can be quite unpredictable and variable, with some days up to 80° F and others at/near freezing temperatures.  Heavy rain and wind, hail, and snow are all possible, as are very hot sunny days.  Warm clothing and layers are all necessary, including rain gear.  A day pack (medium sized backpack) is important for all students so they can carry sufficient clothing and food every day, including 2-3 large water bottles.  Suncreen, winter hats and gloves, sunglasses, and sturdy hiking shoes/boots are key for student safety and comfort.


Conducting a research project at an early career stage is not only a résumé-builder, but helps to develop many skills that are applicable after the summer is over. Working and living together in the field, collaboratively completing a project from start to finish, and starting to develop a network of friends and colleagues all build resiliency, capabilities, and cognitive abilities.  This Gateway Keck project offers these experiences in a supportive yet challenging environment. Students will work on real scientific questions, using standard and state-of-the art field and lab equipment; they will also receive training in science communication, including informal interactions with the public in the field, and more formal methods of presenting information such as lightning talks and giving better, more engaging research presentations.


Anderson, H., MacGregor, K.R., Oddo, P., Riihimaki, C., Williams, C., Myrbo, A.  (in prep). Little Ice Age and human impacts in eastern Glacier National Park, Montana, USA. Proceedings of the National Academy of Sciences.

Brunelle, A. and Whitlock, C., 2003. Postglacial fire, vegetation, and climate history in the Clearwater Range, northern Idaho, USA. Quaternary Research 60, 307-318.

Brunelle, A. et al., 2005. Holocene fire and vegetation along environmental gradients in the northern Rocky Mountains. Quaternary Science Reviews 24, 2281-2300.

Carrara, P.E., 1995. A 12000 year radiocarbon date of deglaciation from the Continental Divide of northwestern Montana. Canadian Journal of Earth Sciences 32, 1303-1307.

Carrara, P.E., 1993. Glaciers and glaciation in Glacier National Park, Montana. Open-File Report 93-510, 1-18.

Carrara, P.E., 1990. Surficial geologic map of Glacier National Park, Montana.1:100,000, .

Carrara, P.E., 1989. Late Quaternary and vegetative history of the Glacier National Park region, Montana.1902, 64 p.

Carrara, P.E., 1987. Holocene and latest Pleistocene glacial chronology, Glacier National Park, Montana. Canadian Journal of Earth Sciences 24, 387-395.

Craig, D.R., Yung, L., Borrie, W.T., 2012. “Blackfeet Belong to he Mountains”: Hope, Loss, and Blackfeet Claims to Glacier National Park, Montana. Conservation and Society, Vol. 10 (3), p. 232-242. DOI: 10.4103/0972-4923.101836

Doerner, J.P. and Carrara, P.E., 2001. Late quaternary vegetation and climatic history of the Long Valley area, west-central Idaho, U.S.A. Quaternary Research 56, 103-111.

Doerner, J.P. and Carrara, P.E., 1999. Deglaciation and postglacial vegetation history of the West Mountains, west-central Idaho, U.S.A. Arctic, Antarctic, and Alpine Research 31, 303-311.

Earhart, R.L. et al., 1989. Geologic maps, cross section, and photographs of the central part of Glacier National Park, Montana.

Fink, G., Wessels, M., Wuest, A., 2016. Flood frequency matters: Why climate change degrades deep-water quality of peri-alpine lakes.  Journal of Hydrology 540, 457-468.

Hanauer, D.I., Graham, M.J., Hatfull, G.F. 2016. A Measure of College Student Persistence in the Sciences (PITS). CBE-Life Sci Educ vol. 15, no. 4, ar54. doi: 10.1187/cbe.15-09-0185CBE

Hofmann, M.H. et al., 2006. Late Pleistocene and Holocene depositional history of sediments in Flathead Lake, Montana; evidence from high-resolution seismic reflection interpretation. Sedimentary Geology 184, 111-131.

Horodyski, R.J., 1983. Sedimentary geology and stromatolites of the Mesoproterozoic belt
Supergroup, Glacier National Park, Montana. Precambrian Research 20.

Karsian, A.E., 1995. A 6800-year vegetation and fire history in the Bitterroot Mountain Range, Montana. MSc. Thesis, University of Montana, Missoula. 54 p.

Key, C.H., D.B. Fagre, R.K. Menicke. 2002. Glacier retreat in Glacier National Park, Montana. In R.S. Williams and J.G. Ferrigno, eds., Satellite image atlas of glaciers of the world: North America. U.S. Geological Survey Professional Paper 1386-J, U.S. Government Printing Office, Washington D.C. p 365-381.

Klasner, F. L. and D. B. Fagre. 2002. A half century of change in alpine treeline patterns at Glacier National Park, Montana, U.S.A. Arctic, Antarctic, and Alpine Research. 34(1):53-61.

MacGregor, K.R., Riihimaki, C.A., Myrbo, A., Shapley, M.D., Jankowski, K. 2011. Geomorphic and climatic change over the past 12,900 years at Swiftcurrent Lake, Glacier National Park, Montana. Quaternary Research, 75(1), doi:10.1016/j.yqres.2010.08.005.

MacLeod, D.M. et al., 2006. A record of post-glacial moraine deposition and tephra stratigraphy from Otokomi Lake, Rose Basin, Glacier National Park, Montana. Canadian Journal of Earth Sciences 43, 447-460.

Mehringer, P.J.,Jr et al., 1984. The age of Glacier Peak tephra in west-central Montana. Quaternary Research 21, 36-41.

Millspaugh, S.H. et al., 2000. Variations in fire frequency and climate over the past 17 000 yr in central Yellowstone National Park. Geology 28, 211-214.

Schachtman, N., MacGregor, K.R., Myrbo;, A. Hencir, N.R., Riihimaki, C.A., Thole, J., Bradtmiller, L. (2015). Lake core record of Grinnell Glacier dynamics during the Late Pleistocene and Younger Dryas, Glacier National Park, Montana, U.S.A. Quaternary Research, v. 84, no. 1, p. 1-11, doi:10.1016/j.yqres.2015.05.004

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Structural evolution of a normal fault transfer zone

Structural evolution of a normal fault transfer zone

Structural evolution of a segmented normal fault transfer zone, Sevier fault, southern Utah

Overview: This four-student project focuses on the evolution of the Sevier normal fault zone in southern Utah, near Zion National Park. The Sevier normal fault, considered one of the most important structures in the Basin and Range province (e.g., Davis, 1999; Lund et al., 2008), is part of the Toroweap-Sevier fault system, which extends for more than 300 km from northern Arizona to southern Utah (Fig. 1). The fault has accommodated extension across the transition zone from the Basin and Range province to the relatively stable Colorado Plateau since the Miocene (e.g., Reber et al., 2001; Lund et al., 2008), and previous workers have noted the potential of the fault to produce significant earthquakes (Anderson and Rowley, 1987; Doelling and Davis, 1989; Anderson and Christenson, 1989; Lund et al., 2008).


Geologist sketching an outcrop in the Navajo sandstone, southern Utah

For this project, we plan to examine the transfer zone between two major segments of the Sevier fault system, where a network of subsidiary faults and fractures has developed during fault propagation and slip. Because these structural features are so well exposed in the spectacularly-crossbedded Jurassic Navajo and Temple sandstones, we can use those features to shed light on how the stress field has affected the intensity of fracturing and faulting both horizontally and vertically in relation to the major fault segments.

Students projects will focus on the evolution of this major normal fault transfer zone, using a combination of field data collection, petrographic analysis of sandstones and fracture fill, 3D computer modeling of fault evolution, fracture intensity and propagation analysis, drone-based image analysis, and 3D computer modeling of stress-strain fields during fault propagation.

When: June 15-July 13, 2018

Where: Glendale, Utah (field work) and San Antonio, Texas (lab work)

Who: Four students and project leader Dr. Ben Surpless, Trinity University,

Prerequisites and Recommended Courses: Suggested (but not required) are core courses in the Geology major: Historical Geology, Structure/Tectonics, Stratigraphy, Mineralogy, and Petrology. Students should have completed key cognate courses in Chemistry and Math. Experience at a field camp or in a field geology course is recommended but not required. We are particularly interested in applicants with an interest in structural geology, who have a high degree of comfort in outdoor settings, are flexible eaters, and who want to use this work to complete a senior thesis (or equivalent) in geology.

Expectations and Obligations:
1. Participation in field work and data analysis during the summer (June 15-July 13, 2018)
2. Write an abstract and present a paper for the Geological Society of America Cordilleran Section Meeting in Portland, Oregon (abstracts due Feb. 7, 2019; conference is May 15-17, 2019).
4. Write a short contribution (4-6 pages text + figures) to be published in the Proceedings of the Keck Geology Consortium 2019 Volume (first draft due Mid-February).
5. Expected but not required: Use this work for the completion of a senior thesis (or equivalent) at your home institution.

Figure 1: Physiographic context for the Sevier fault zone study area within the Basin and Range‐Colorado Plateau transition zone (see inset). In combination with the Grand Wash, Hurricane, and Paunaugunt faults, the Sevier‐ Toroweap fault helps accommodate extension across the transition zone. Ball is on the hanging wall of the west‐dipping faults. Detailed geology of the Sevier fault study area (boxed) is displayed in Figure 2. Digital shaded relief modified from Thelin and Pike (1991). Figure significantly modified from Reber et al. (2001).


Geologic Overview

The study area (Fig. 2) is part of a particularly complex portion of the Sevier normal fault, termed the Orderville geometric bend (e.g., Reber et al., 2001), with a range of transfer zone geometries exposed at different locations along the NNE-striking, west-dipping system.  Figure 2 displays the fault network that accommodated extension along the Orderville bend, from the Elkheart Cliffs area in the south to the area north of Stewart Canyon. The bold yellow fault traces represent the dominant, high-displacement faults across the study area.  The interaction of these fault systems is responsible for the formation of the relay ramps shown adjacent to Stewart Canyon and Red Hollow Canyon, and white faults represent lower-displacement normal fault systems that helped accommodate extension, likely evolving within the perturbed stress field associated with the transfer zones between dominant faults.

Recent studies (e.g., Davis, 1999; Schiefelbein and Taylor, 2000; Schiefelbein, 2002; Doelling, 2008) and reconnaissance work by Trinity University undergraduates (Mathy et al., 2016; Simoneau et al., 2016) have revealed locations within the Orderville geometric bend that preserve fault geometries related to different stages of transfer zone evolution along the Sevier fault zone of southern Utah.  These studies have also established a well-defined structural framework for detailed analysis of the subsidiary structures (e.g., relay ramps, minor faults, fractures, deformation bands) that form as synthetic normal fault segments propagate and link (Fig. 3).

Figure 2: Fault map of the Sevier fault transfer zone near Orderville, Utah. Yellow lines indicate normal faults that accommodate significant (>100 m) displacement or play an important role in fault linkage, and white lines indicate normal faults that play a role in strain accommodation but display lesser displacements. Ball symbols are on the hanging wall. Study locations are indicated by numbers in circles, and relay ramps within the transfer zone are labeled with red text. Faults shown here are based primarily on Schiefelbein (2002) and on the results of summer 2016 field research. See Figure 1 for location.

Figure 3: Diagrams displaying relay ramp development, fault capture, and damage zone classification. A) In all diagrams, the dark gray shaded area represents the magnitude of displacement, and the lines represent the slip direction as the hanging wall drops relative to the footwall. 1. A system of small‐displacement faults develops to accommodate upper crustal stresses. The dotted lines represent the future propagation of the faults. 2. As displacement increases across the system, two faults (1 and 2) become dominant, both lengthening in map view and displaying increasing total displacement. A relay ramp forms in the zone of overlap between the faults. 3. Faults 1 and 2 link as a new cross‐fault connects them. A future cross‐fault may form where indicated, fully breaching the relay ramp. B) Map‐view of a segmented fault system (bold lines are faults), with 1 and 2 representing progressive stages of fault segment linkage and capture. In 1, the three fault segments overlap but are only soft linked, and in 2, one of the segments has “captured” displacement from the other segments, isolating the overlapped portions of segments (red lines) that are no longer active. The segments are now hard linked and act as a single, corrugated fault. Arrows show the direction and relative magnitude of fault slip projected onto plan view. C) Schematic map view diagram of damage zone types associated with a segmented normal fault system (bold lines) with ball symbols on the hanging wall. Figure A. adapted from Peacock (2002) and Long and Imber (2011), Figure B. adapted from Reber et al. (2001), and Figure C. adapted from Kim et al. (2004).

Study Area

The excellent vertical and lateral exposure of the Jurassic Navajo and Temple Cap sandstones at the three primary study sites (Fig. 2) provides the opportunity to directly observe faults, fractures, and deformation bands within these well-studied lithologies (e.g., Rogers et al., 2004; Schultz et al., 2010; Solom et al., 2010), especially within the context of the mapped transfer-zone fault networks.  The Elkheart Cliffs exposure at location 1 (Fig. 2) displays the simplest fault geometry because all E-W extension is accommodated by a single fault.  In contrast, location 2 (Red Hollow Canyon) displays a more complex fault system with a single relay ramp, and location 3 (Stewart Canyon) displays the most complex fault network, including 3 relay ramps (Fig. 2).  This spatial variation in fault complexity allows us to treat these locations as “snapshots” in time, capturing “moments” of growing fault zone complexity, permitting us to evaluate how the evolution of different fault geometries and complexities damages adjacent rock volumes (Fig. 3).

Goals and Significance of the Project

Our findings will shed light on how stress and strain in fault transfer zones vary spatially and evolve temporally across a range of scales.  Because rocks in the study area are so well exposed, we can use results from this research to address the 3D evolution of rock volumes associated with similar fault zones in the subsurface.  Brittle features, when formed in the subsurface, impact on the flow of fluids, including water and oil.  Additionally, this research may reveal how strain is diffused at fault segment boundaries during earthquake events, thus impacting the assessment of seismic hazard in similar systems elsewhere.  Related goals of this project include:  1) development of retro-deformable 2D and 3D models of the fault transfer zone, based on both published and new data, which we can test using industry-grade computer modeling software; 2) assessment of stress and strain fields, in the context of field data, that evolved during the vertical and lateral propagation of major fault segments using 3D computer modeling software; and 3) construction of a viable model of subsidiary structure formation in the context of rock properties and relative to the major fault segments mapped in the field.  This project allows students to perform structural field research and computer modeling of a major, segmented normal fault in the regionally important transition zone between the eastern Basin and Range Province and the Colorado Plateau, and the ideas developed during this project will inform our understanding of the complex evolution of normal fault transfer zones worldwide.

Potential Student Projects

1. Structural evolution of the Orderville geometric bend, Sevier fault zone. This student would use published maps and new map data to construct accurate structural cross-sections across the Orderville geometric bend. When combined with existing cross sections, this student can then perform 3D computer modeling in Move2017 to build and test a complete 3D model of the fault system from surface to depth. An important part of this work would be to shed light on how faults in similar systems propagate and link both horizontally and at depth.

2. Predicting changes in strain accommodation associated with increasing fault zone complexity. This student would use a combination of field data, structural analysis of faults and fractures, cross-section construction, and 3D modeling using the Move2017 Fault Response Module to investigate how total fault displacement changes along strike within the Orderville geometric bend (location 1 vs. location 2 vs. location 3). They would build 3 primary models, constrained by field and existing map data, to evaluate the characteristics of fracture systems that develop in fault systems of varying complexity. When the student compares model results with field data and mapped fault patterns, they can develop hypotheses for strain accommodation and permeability development in rocks affected by fault systems of varying complexity.

3. Predicting fault damage zones associated with horizontal propagation of overlapping normal faults. This student would use a combination of field data, mapped faults, fracture analysis, and 3D computer finite-element modeling using Abaqus to investigate two of the best-constrained (i.e., precisely mapped, with measurable displacements and well-documented fractures) faults within the system. This student would also likely use thin section petrography to document changes in both lithologic characteristics and fracture fill textures and compositions in relation to the faults they test with modeling. In several cases, fault displacements decrease from 10s of meters of displacement to 0-m displacement (at the fault tip) over 100s of meters along strike, permitting the student to develop a model of coupled lateral fault propagation-fracture network development.

4. Changing stress-strain fields within a complex normal fault transfer zone. This student would use a combination of field data, mapped faults, fracture analysis, and 3D computer modeling using the Move2017 Fault Response Module to investigate how different fault geometries and overlaps affect the stress field and create subsidiary structures (mostly fractures). This student would choose several of the better constrained en echelon fault geometries (e.g., no overlap, some overlap, significant overlap, hard-linked) to build and test 3D models of fracture development. This student would also likely use thin section petrography to document changes in both lithologic characteristics and fracture fill textures and compositions. These model results and petrographic analysis results could then be compared to field data, permitting the student to address how stress and strain vary in different cases of synthetic normal fault interactions.

5. Fault damage analysis within a complex normal fault transfer zone. This student would use a combination of field data, mapped faults, fracture analysis, and 3D computer modeling using Photoscan Professional to investigate how fracture networks vary in cross-sectional exposures of the fault network exposed in Stewart and Red Hollow Canyons (Fig. 2). These 3D models will become the virtual outcrops that this student can use to analyze changes in fracture intensities and orientations both horizontally (relative to mapped faults) and vertically (relative to changes in lithology). This student would also perform some petrographic analysis, especially investigating changes in lithology that might impact fracture development. The results of this student’s analysis would inform our understanding of fluid-flow potential associated with similar fault networks in the subsurface.


Field Work: Our tentative field dates are June 15 – June 29, 2018.  Students will fly to San Antonio on June 15, and on June 16, the project team will depart San Antonio in 2 Trinity field vehicles, staying for one night in Albuquerque, NM, arriving at Bauer’s Canyon Ranch RV Park and Campground in Glendale, Utah, on the night of June 17.  We will stay at Bauer’s Canyon Ranch RV Park from the night of the 17th until the night of June 27, performing fieldwork in the nearby canyons (11 nights at the RV park).  We will purchase food in Orderville and prepare all meals in the RV park (which has shower and laundry facilities).  During our time in the field, we will visit Zion National Park, where the same rock units are spectacularly exposed.  Students will have access to power and wifi throughout our time at the RV park, so students can perform significant database building and field data analysis while in the field.

Students will be expected to carry medium-sized field packs with field equipment, lunches, and water every day in the field.  Although hiking will be involved, we will not be hiking in rugged topography where safety is an issue.  We will never be more than 2 miles from our field vehicle, and in most cases, we will not be more than 3 miles from a city or town.  Although we will be performing fieldwork in late June, the students and I will perform most fieldwork starting at 7 am and ending at about 2 pm, in order to avoid the hottest temperatures (commonly in the low- to mid-90s).  In the afternoon, we will compile field data and discuss our findings in the context of the research questions.  On June 28 – June 29, we will drive back to San Antonio, TX, staying in Albuquerque, NM for one night.

Lab and Analytical Work: Students would work in the Geosciences department at Trinity University from June 30 – July 12, staying in Trinity’s dorms with other summer research students.  Most dorms have kitchen facilities so meals can be prepared on campus.  Many on-campus (non-Keck) research students will have access to cars, or alternatively, there is an on-demand hourly or daily car-rental system), so students can leave campus to purchase food.  During this two-week period, all 4 students will focus on analyzing field data, cutting billets for thin sections, learning to use the 3D computer modeling software necessary for their project, and developing a research proposal and timeline for the rest of the academic year.  Students will depart San Antonio on July 13.


We plan to take all participants to the GSA Cordilleran section meeting in Portland, Oregon (15–17 May 2019). We hope most students will be first author on one paper, and probably secondary authors on others due to the collaborative nature of the project.

All students are required to complete a 4-6 page paper (short contribution) that will be published in the Proceedings of the Keck Geology Consortium 2019 Volume (see examples from previous years). The first draft of this paper will be reviewed by your research advisor at your home institution sometime in late February, 2019, with the revised version sent to the project directors by March 1. Final versions of your paper and figures will be submitted to the Keck Office in Mid-March.


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Simoneau, S., Surpless, B., and Mathy, H., 2016, The evolution of subsidiary fracture networks in segmented normal fault systems: GSA National Meeting, Abstracts with Programs, Denver, Colorado.

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Geology of the Chugach-Prince William terrane

Geology of the Chugach-Prince William terrane

Geology of the Chugach-Prince William terrane in northern Prince William Sound, Alaska

Overview:  This six-student project focuses on the geology of the Chugach-Prince William terrane in southern Alaska, and is part on an ongoing study of the tectonic history of the western North American Cordillera. The Chugach-Prince William terrane is a thick accretionary complex dominated by Campanian-Paleocene (c. 75-55 Ma) trench fill turbidites that were likely derived from the Coast Plutonic Complex (CPC) in British Columbia as indicated by sandstone provenance, isotopic data, and detrital zircon ages (Sample and Reid, 2003; Haeussler et al., 2005; Bradley et al., 2009; Amato and Pavlis, 2010; Garver and Davidson, 2015; Davidson and Garver, 2017). These rocks are interbedded with and intruded by mafic volcanic rocks (pillows, sheeted dikes, and gabbro), and were intruded by near-trench plutons of the Sanak-Baranof belt (63-47 Ma) and younger Eshamy Suite of plutons (37-39 Ma). For this project, we plan build on the results from key field areas in Prince William Sound and extend the reach of a critical area we visited with Keck projects in 2011 and 2014 (Garver and Davidson, 2012; Davidson and Garver, 2015).  Student projects will focus on the provenance of these rocks including U/Pb dating and Hf isotope studies of detrital zircon, sedimentology and stratigraphy of turbidites and associated conglomerates, igneous petrology of the interbedded mafic rocks, and igneous petrology, U/Pb dating, and Hf isotopic studies of the Eshamy plutons.

Turbidites on the SW shore of Hinchinbrook Island, Prince William Sound, Alaska

When: June 16-July 9, 2018

Where: Southern Alaska: [1] Gathering and field trips in Anchorage and staying at the University of Alaska-Anchorage, [2] stay in Valdez with road and boat work in Prince William Sound, [3] Put in a remote camp by boat in northern Prince William Sound.

Who: Six students and project Leaders: John I. Garver (Union College) and Cam Davidson (Carleton College)

Prerequisites and Recommended Courses: Suggested (but not required) are core courses in the Geology major: Historical Geology, Structure/Tectonics, Stratigraphy, Mineralogy, and Petrology. Students should have completed key cognate courses in Chemistry and Math. Experience at a field camp or in a field geology course is recommended but not required.  We are particularly interested in applicants with an interest in Tectonics, who have a high degree of comfort in rough outdoor settings, are flexible eaters, and who want to use this work to complete a senior thesis (or equivalent) in geology. Helpful, but not required in the letter of recommendation from the on-campus sponsor is an indication of how well the applicant will function in a remote field setting with primitive camping.

Expectations and Obligations:
1. Participation in field work during the summer (June 16-July 9, 2018)
2. Follow up sample preparation and/or analytical work that may include a one week visit to the University of Arizona Laserchron Center in late November or early December.
3. Write an abstract and present a paper (poster or talk) for the Geological Society of America Cordilleran Section meeting in Portland, Oregon (abstracts due Feb. 7, 2019; conference is May 15-17, 2019).
4. Write a short contribution (4-6 pages text + figures) to be published in the Proceedings of the Keck Geology Consortium 2019 Volume (first draft due Mid-February).
5. Expected but not required: Use this work for the completion of a senior thesis (or equivalent) at your home institution.


Geologic Overview

The Chugach-Prince William (CPW) composite terrane is a Mesozoic-Tertiary accretionary complex that is well exposed for ~2200 km in southern Alaska and is inferred to be one of the thickest accretionary complexes in the world (Plafker et al., 1994; Cowan, 2003).  The CPW terrane is bounded to the north by the Border Ranges fault, which shows abundant evidence of Tertiary dextral strike slip faulting, and inboard terranes of the Wrangellia composite terrane (Peninsular, Wrangellia, Alexander) (Pavlis, 1982; Cowan, 2003; Roeske et al., 2003).  Throughout much of the 2200 km long belt of the CPW terrane it is bounded by the offshore modern accretionary complex of the Alaskan margin, but east of Prince William Sound the Yakutat block is colliding into the CPW and this young collision has significantly affected uplift and exhumation of inboard rocks (Fig. 1).

Figure 1: Map of southern Alaska showing the distribution of rocks in the Chugach-Prince William terrane (green) and the Yakutat terrane (yellow), which is colliding with Alaska.

Very soon after imbrication and accretion to the continental margin, rocks of the CPW were intruded by near-trench plutons of the Sanak-Baranof belt that has a distinct age progression starting in the west (63 Ma in the Sanak-Shumagin areas far to the west) and getting progressively younger to the east (53-47 Ma on Baranof Island; Bradley et al., 2000; Haeussler et al., 2003; Kusky et al., 2003; Farris et al., 2006; Wackett et al., in revision).  In western Prince William Sound, these rocks were also intruded by the 37-39 Ma Eshamy Suite of plutons (Johnson, 2012, see Fig 3).

Paleomagnetic and geologic data indicate that the CPW has experienced significant coast-parallel transport in the Tertiary (see Garver and Davidson, 2015).   The CPW has apparent equivalents to the south, and this geologic match suggests that in the Eocene, the southern part of the Chugach-Prince William terrane was contiguous with the nearly identical Leech River Schist exposed on the southern part of Vancouver Island (Cowan, 1982; 2003). The geological implication of this hypothesis is profound yet elegant in the context of the Cordilleran tectonic puzzle: the CPW is the Late Cretaceous to Early Tertiary accretionary complex to the Coast Mountains Batholith Complex that intrudes the Wrangellia composite terrane and North America.  Thus, the CPW is inferred to have accumulated in a flanking trench to the west and then soon thereafter these rocks were accreted to the margin.  This geologic match is elegant because it suggests that the CPW accumulated outboard the Coast Mountains Batholith Complex (Gehrels et al., 2009) and that the CPW essentially is the erosional remnants of that orogenic belt.  Thus, the focus of this proposal is on the very thick rocks of the CPW accretionary terrane that were intruded by near trench plutons and then translated some controversial distance along the North American margin in the early Tertiary.  This late-stage translation by strike-slip faulting is of critical importance to this project.

Study Area

For the 2018 field season we plan to extend and expand on the transect across the CPW we completed in 2014 and adjacent to work done in 2011 (Fig. 2, 3).  Preliminary data from two samples collected on the Richardson Hwy northeast of Valdez show that rocks correlative to the Paleocene-Eocene Orca Group are much more extensive than originally thought (Davidson and Garver, 2017). We now know that these younger rocks occur inboard of Valdez, in the Chugach Metamorphic complex, in the Schist of Nunatak Fiord, and in the Baranof Schist (Gasser et al., 2011; Rick et al., 2014; Olson et al., 2017). This result means that Paleocene and Eocene Orca rocks occur to the west, north, and east of the Yakutat Collision zone.

Figure 2: Geology of the southern Alaska margin centered on the Yakutat terrane collision (yellow) and the Chugach-Prince William terrane (shaded in green) .  Our work in the Prince William Sound area is focused on two transects (A, B). We now recognize that large-scale imbrication by strike-slip faulting plays a crucial role in shaping the distribution of rocks of the Orca Group (light green), our primary focus. Location of this proposed Keck project shown is in transect B, and our proposed field in northern Prince William Sound is show in Figure 3. Map modified from Gasser et al. (2011).

Figure 3:  Geologic map of study area focused on Prince William Sound (PWS) in southern Alaska.  Our previous work in PWS in 2011 and 2014 allowed us to build a framework for understanding the Orca Group (most olive in map), and part of that framework involved the recognition that strike-slip faults play an important role in juxtaposing different facies, and in driving differential exhumation. Our proposed work is partly focused on documenting facies changes (provenance) across the Western Gravina fault and the Jack Bay fault (aka Contact fault). Map modified from Wilson et al. (2015).

Goals and Significance of the Project

The primary goal of this project is to sort out the age, source, and timing of accretion of the Valdez and Orca turbidites and subsequent strike-slip motion along the Contact fault and allied structures (i.e. Jack Bay, West Gravina, Rude River) associated with the collision of the Yakutat plate in eastern Prince William Sound (Fig. 2).  Ancillary goals of this project include: 1) comparing the age and geochemistry of interbedded mafic volcanic rocks of the Orca Group with the Knight Island and Resurrection ophiolites to the west and south (Fig 3); and 2) compare the crystallization age and petrology of undated Eshamy Suite plutons with those previously studied by our group to the southwest (2011 site, see Johnson, 2012).

This project is significant because it will allow students to work in units that are classic in Cordilleran tectonics, and the results will directly feed into ideas of terrane translation and development of the Cordilleran tectonic collage.

Student Projects

  1. Provenance and maximum depositional ages of sandstones and conglomerates (2-3 students). Our preliminary work along the Richardson Highway north of Valdez suggests that the contact relationships between the Valdez Group (Campanian-Maastrictian) and Orca Group (Paleocene-Eocene) is much more complicated than currently mapped (as shown in Figure 3 derived from Wilson et al., 2015). One of the goals of this project is to use U/Pb and Hf isotope data of detrital zircon from two transects across the Contact fault (Jack Bay) to help define the extent of these two units (Fig. 2).  Our working hypothesis is that the turbidites of the CPW are imbricated in vertical panels by strike slip faulting, juxtaposing rock packages with different MDA’s and provenance (indicated by unique U/Pb and Hf detrital zircon signatures).  Cobble and pebble conglomerates containing sandstone and plutonic clasts are common in the Orca Group in this area.  At least one student will determine the provenance and age of these clasts to see if sandstones from the older Valdez Group is being exhumed and shed into the basin during deposition of the Orca Group.
  2. Core-Rim dating (1-2 students). Core-rim dating will allow us to determine high-grade metamorphic source regions because important and distinctive rims on zircon may form during metamorphism. Our initial experiments at LaserChron show we can successfully date rims with a 10 or 12 um laser spot size (Fig. 3). There are a number of reactions that drive changes in zircon in the metamorphic environment, and these include: 1) recrystallization; 2) fluid alteration; 3) subsolidus nucleation; 4) precipitation from aqueous fluids; and 5) precipitation from melts during anatexis (Hoskin and Black, 2000; Xie et al., 2009). We focus here on two commonly recognized rims that form under high-grade metamorphic conditions (upper amphibolite and granulite). One type of rim typically appears dark in CL images, shows little internal structure, and has relatively high uranium, high U/Th, and low REE contents and results from zircon growth under metamorphic conditions (Ksienzyk et al., 2012). The other type of rim is CL-bright, with irregular re-crystallization fronts and relict zoning, and variable U/Th and REE concentrations that typically form during solid-state recrystallization of zircon (Hoskin and Black, 2000; Hoskin and Schaltegger, 2003; Xie et al., 2009; Ksienzyk et al., 2012). In these recrystallization rims, the U/Th ratio increases primarily due to Th loss, and the isotopic system is progressively reset due to expulsion of radiogenic lead (Hoskin and Black, 2000; Hoskin and Schaltegger, 2003). This project will use core-rim dating to determine metamorphic events in the source region, which likely included the Central Gneiss Complex of the Coast Plutonic Complex located to the south in British Columbia.

Figure 4: Two core-rim dated zircons from the Yakutat Group showing Precambrian cores and Cretaceous rims. [A] Precambrian core with oscillatory zoning, and CL-bright rim with possible recrystallization front and relict zoning. [B] Zoned Precambrian core, and complicated CL-dark high-uranium rims. Our earlier work using Raman (see below) suggested the radiation damage in these grains was Cretaceous, and this is confirmed by rim dating.

3. Damage dating (1 student). We are developing a technique to use zircon crystallinity to quantify the timing of metamorphism of Precambrian zircon. This new technique aims to quantify accumulated radiation in Precambrian zircon using degree of crystallinity measured by μ-Raman spectroscopy as indicated by the position of the ν3(SiO4) or the FWHM of the ν3(SiO4) (Marsellos and Garver, 2010; Garver and Davidson, 2015). In essence, this is radiation damage dating where the accumulated damage is used as a chronometer and can reveal the age of last metamorphism. We have made important advances in developing this technique so it can be used to solve tectonic problems with DZ data sets, and we have shown that disorder in Precambrian zircons in the CPW fall into two distinct arrays of radiation damage (Fig. 4). One cohort of Precambrian grains has been cool since the lower Paleozoic and another since the Cretaceous (Garver and Davidson, 2015). We are excited that this technique can be tremendously important for detrital studies, but more work is required to calibrate damage and Raman active modes. For this project, a student will use this technique to determine metamorphic histories of Precambrian zircon from the Orca and Valdez groups.

Figure 5: Raman shift for Precambrian zircon from the CPW (from Garver and Davidson, 2015).

4. Age and origin of mafic volcanic rocks in the Orca Group (1 student). Pillow lavas and sheet flows of mafic volcanic rocks are interbedded with the Orca Group; and on Glacier Island, pillow basalts, sheeted dikes, and gabbro are reported (Nelson et al., 1999). This project involves collecting major and trace element data from the mafic volcanic rocks throughout the area and to compare these data with previously published data from similar rocks to the south and west (Miner, 2012; Young, 2015), and the Resurrection and Knight Island ophiolites (Lytwyn et al., 1997; Miner, 2012).

5. Age and origin of the Eshamy Suite plutons (1 student). Our previous work in western Prince William Sound helped define the age and geochemistry of a unique series of 37-39 Ma gabbroic to granodiorite plutons that intrude the CPW accretionary wedge complex (Johnson, 2012). This project will work on two or three plutons near Valdez (Miner’s Bay, Cedar Pluton) that have been tentatively correlated to the Eshamy Suite based on major element geochemistry and K-Ar dates (Nelson et al., 1999). The goal of this project is to confirm the age of these plutons using U/Pb geochronology and to use whole rock major and trace elements, and Hf isotope data from zircon to help describe the petrogenesis of these rocks.


Field Work: Our tentative dates are June 16 – July 9, 2018.  We will meet in Anchorage and spend a few days introducing everyone to the CPW geology near Anchorage, and meet with geologists at the USGS.  Then we travel to Valdez (Fig 3) where we will spend part of the time working out of Valdez to access the eastern transect (Fig 3, 18A), and the rest of the time (about a week) in a remote camp near Glacier Island, southwest of Valdez (Fig 3, 18B)

Analytical Work: Students will cut billets for thin sections at their home institution and thin sections will be made by the expert technician at Union College. Mineral separates will be done at Union or Carleton in late summer and early fall.  Imaging zircon sample mounts on the SEM (BSE and CL) can be done at Carleton, Union, or the student’s home institution if they have the equipment.

U-Pb and Hf analyses will be done at the University of Arizona Laserchron Center in late November or early December, and this is an important time for the entire Keck team to reconvene and collect critical data.  We will invite all students to participate in this excursion, whether they are using U/Pb data in their thesis or not.  Data reduction is done onsite, so students will leave with their data set.

Keck students in the LaserChron center at the University of Arizona during a 3-5 day session in November.


Davidson and Garver have been doing research in the northern Pacific Rim for over 30 years (each) with primary field areas in Kamchatka, Alaska, British Columbia, and Washington.  Thus we are familiar with safety issues primarily those related to Bears and Boats.  There is little question that there are a host of inherent risks in this proposed work.  Here we briefly address the most common concerns.

Bears.  The primary issue is Black and Brown Bears. We will spend the bulk of our time in coastal waters as a group, hence our exposure is minimal.  We note that our field season coincides with the Sockeye run, so almost all bears (black or brown) tend to be pre-occupied with fish.  We train all participants in the use of bear deterrents.  We will have bear bangers (a small pen-sized explosive charge) and Bear Spray for everyone.

Boats and Communication.  We will be using two 15 ft Zodiac inflatable boats with aluminum floors and 30 hp 4-stroke engines.  All participants will be instructed in safe boating practices including protocol for VHF radio use and will be required to wear life jackets. We also have a satellite phone for emergencies.


We plan to take all participants to the GSA Cordilleran section meeting in Portland, Oregon (15–17 May 2019).  We hope most students will be first author on one paper, and probably secondary authors on others due to the collaborative nature of the project.

All students are required to complete a 4-6 page paper (short contribution) that will be published in the Proceedings of the Keck Geology Consortium 2019 Volume (see examples from previous years). The first draft of this paper will be reviewed by your research advisor at your home institution sometime in late February, 2019, with revised version sent to the project directors by March 1.  Final versions of your paper and figures will be submitted to the Keck Office in Mid-March.


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