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, [email protected]), and Dr. Jade Star Lackey (Pomona College, [email protected])

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.

PROJECT DESCRIPTION

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.

PROJECT LOGISTICS

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.

PROFESSIONAL DEVELOPMENT

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.

References

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.

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, m[email protected]), and Dr. Amy Myrbo (LacCore/CSDCO, University of Minnesota, [email protected])

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).

PROJECT DESCRIPTION

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 (https://e360.yale.edu/features/greenlock-a-visitor-crush-is-overwhelming-americas-national-parks). 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.

PROJECT LOGISTICS

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.

GNP SAFETY ISSUES

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.

PROFESSIONAL DEVELOPMENT

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.

References

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

Shapley, M.D. et al., 2009. Late glacial and Holocene hydroclimate inferred from a groundwater flow-through lake, northern Rocky Mountains, USA. The Holocene.

Whipple, J.W., 1992. Geologic map of Glacier National Park, Montana.1:100,000.

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