Wyoming PETM

Wyoming PETM

Body size evolution of the first mammalian megaherbivore during Paleogene hyperthermal events, Wyoming

Overview: This project aims to understand the evolution of body size in Coryphodon, the first mammal to evolve large body size. Coryphodon was common across the northern hemisphere through much of the Paleogene, a time of tumultuous environmental and climatic change. In North America, Coryphodon experienced at least one dwarfing event during this period, halving and doubling its body mass in quick succession. Through a combination of field and laboratory work, undergraduate students will investigate the processes underlying body size evolution in Coryphodon, asking how and why climatic and environmental change may have affected the rate and duration of its growth. This project integrates knowledge and skills from earth and life sciences to answer fundamental questions about the mechanisms underlying body size evolution in the face of dramatic environmental change.

Figure 1: Students looking for fossils in the Paleogene of Wyoming.

When: June 14 – July 10, 2019

Where: Fieldwork will take place in Wyoming’s northern Bighorn Basin. Lodging will be a ~30 minute drive north, in Red Lodge, Montana.

Who: Six undergraduate students and Project Directors Dr. Michael D’Emic ([email protected]) and Dr. Simone Hoffmann ([email protected]). Collaborator Dr. Brady Foreman (Western Washington University) will join for the first week of the fieldwork and provide additional mentorship. Collaborator Dr. Elis Newham (University of Bristol) will contribute to cementum analysis after fieldwork.

Prerequisites and Recommended Courses: Required courses are at least two introductory-level geology and/or biology and cognate courses in chemistry and math. Suggested (but not required) courses include Historical Geology, Earth History Evolution, Anatomy, Stratigraphy/Sedimentology, and Paleontology. Experience at a field camp or in a field geology or biology course is recommended but not required. We are particularly interested in applicants who are comfortable in outdoor/backcountry settings, are able to complete day hikes in warm temperatures (on occasion greater than 95° F in the high desert climate), and who want to use this work to complete a senior thesis (or equivalent).

Expectations and Obligations:
1. Participation in all project-related work during the summer (June 14-July 10, 2019).
2. Follow up data analysis at home institution and regular conference calls with research advisors throughout academic year.
3. Write an abstract and present a paper (poster or talk) for the Geological Society of America Cordilleran meeting in Pasadena, California (conference is 12-14 May, 2020).
4. Write a short contribution (4-6 pages text + figures) to be published in the Proceedings of the Keck Geology Consortium 2020 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.

PROJECT DESCRIPTION

Background and Goals: Climate change affects the resources available to animals, impacting factors such as their geographic ranges, growth rates, and reproductive behaviors. These effects can be measured in the fossil record and used to predict ecosystem change in the future (Barnosky et al., 2017). One of the best-studied examples of past climate change and its effects is the Paleocene-Eocene Thermal Maximum (PETM) at about 56 Ma, which caused massive perturbations in floras (Wing et al., 2005), fluvial landscapes (Foreman et al., 2012), and mammalian evolution (Gingerich, 2003). The PETM was followed by a long-term warming trend during the early Eocene that culminated with the Early Eocene Climatic Optimum (Zachos et al., 2008). This long-term warming trend was punctuated by ‘hyperthermal’ events similar to the PETM during the early Eocene (Abels et al., 2015). In response to the PETM and other hyperthermals, rapid and extreme mammalian dwarfing occurred (Gingerich, 2003; Secord et al., 2012, d’Ambrosia et al., 2017). It is unclear how mammals evolved their smaller body size in terms of growth pattern and duration. The most commonly cited hypothesis is that dwarfing was due to decreased growth rates owing to lower nutrition content of plant resources (Gingerich, 2003). However, this hypothesis has not been tested, and it is equally plausible that smaller body size was achieved by growing at the same rates for a shorter period of time (Palkovacs, 2003). Undergraduates will test these hypotheses using the rich mammal fossil record in the Bighorn Basin of Wyoming, which densely covers the Paleogene.

This project will evaluate the growth mechanisms underlying changes in body size in the Paleogene mammal Coryphodon. Coryphodon is known from hundreds of localities in precisely dated paleosols of the Bighorn Basin, and its bones and teeth preserve annual growth rings that allow individual specimens to be aged. Coryphodon was the first mammalian megaherbivore ever to evolve (body mass > 1000 kg), reaching the size of a small rhinoceros during the mid-Paleocene (Uhen and Gingerich, 1995). Shortly after the PETM, it underwent a dwarfing event to half its body mass only to return to its original size later in the Eocene (Uhen and Gingerich, 1995).

Figure 2: Project director Dr. Michael D’Emic teaching a field course in Wyoming.

Figure 3: Students collecting a rich concentration of fossils from ancient soil beds in Wyoming.

Geologic Setting
Fieldwork will take place in Fort Union and Willwood formations of the northern Bighorn Basin, which are composed of a more than 2,000 m thick sequence of fluvial, floodplain, and minor palustrine deposits (Bown and Kraus, 1981). These extensive strata have been the target of over a century of detailed paleontological fieldwork, resulting in the recovery of tens of thousands of specimens (Gingerich, 2003). Fossil-hosting ancient soil horizons can be resolved temporally to ca. 100,000-year time intervals (Secord et al., 2006). In the case of Coryphodon there appears to be a mismatch between its interpreted semiaquatic lifestyle, inferred from anatomy and oxygen isotope data (Simons, 1960; Fricke et al., 1998), and the well-drained soil horizons it is surface collected from: (Uhen and Gingerich, 2003). We will address this conundrum by collecting detailed sedimentological data to place each newly collected specimen in a paleoenvironmental context.

The Willwood Formation contains a thick accumulation of floodplain deposits. The floodplain strata are characterized by a variety of paleosol sequences linked to short-term and long-term changes in sedimentation and pedogenic processes. A student pursuing this project would excavate specific soil horizons from several locations spanning the early Eocene and tied to the fossil sites collected. Excavation of fresh rock material will allow the student to characterize morphologic features within the soil horizons including ped structures, mottling, development of pedogenic nodules, and trace fossils. Previous studies have developed metrics based on these observations that produce a semi-quantitative record of floodplain drainage conditions and, in some cases, mean annual rainfall. The student would construct a long time series of these conditions spanning the same time frame and stratigraphic positions as the Coryphodon material. Collaborator Brady Foreman has applied this methodology to soil sequences in early Paleogene strata in Colorado and trained both undergraduates and graduate students in this process. Potential scientific questions include “What are the long-term hydrologic conditions in the Bighorn Basin during the early Paleogene?” “How do these paleoclimatic conditions compare to those of other Laramie basins?”

Much of the existing lithostratigraphic information in the northern Bighorn Basin is based on work performed in the late 1970s and early 1980s with the purpose of placing fossil localities in stratigraphic order relative to the K/Pg boundary. More detailed sedimentologic descriptions and assessments of larger stratigraphic changes in river deposition have been performed in isolated intervals focused on the Paleocene-Eocene boundary. A student involved in this project would measure a series of stratigraphic sections to establish long-term changes in fluvial deposition within the northern Bighorn Basin. The student would also perform assessments of biostratigraphy and integrate existing fossil localities and new localities discovered by this project into an updated and more detailed stratigraphic framework. Potential scientific questions include “What are the long-term changes in fluvial deposition and its relationship to climate?” “Is there a relationship between larger-scale fluvial deposition and the productivity and occurrence of fossil localities?”

Figure 4: The campfire ring at field camp, where students will both stay and perform lab work.

Potential Student Projects
Students will conduct fieldwork focusing on collecting new Coryphodon specimens. We will bring newly collected specimens back to the field station where students will prepare, photograph, mold, and cast the fossils. On laboratory days, students will be able to create thin sections of Coryphodon bones and teeth and will take photomicrographs of growth rings in tooth cementum and bones. In the last week of the project, students will estimate body mass for all samples and learn how to analyze growth curves in R. Specifically, students will plot individual age vs. body mass and fit competing growth models to the data using likelihood criteria (analysis in R). Growth models will be compared through time, and maximum growth rate and growth duration will be plotted against paleotemperature estimates to discover potential correlations between mechanisms of body mass evolution and climate. Students will also characterize floodplain drainage and the stratigraphic framework surrounding new fossil findings under the supervision of collaborator Dr. Brady Foreman (see description under ‘Geologic Setting’ above).
Student projects (each student takes the lead on one; collaborations encouraged):
1) bone histology
2) tooth histology
3) growth curve analysis
4) taphonomy/paleoenvironment
5) floodplain drainage
6) stratigraphic framework

Figure 5: Annual growth lines in Coryphodon bones and tooth roots. The number of rings equals the age of the animal and the spacing of the rings indicates how fast the animal grew.

PROJECT LOGISTICS

Project directors D’Emic and Hoffmann have led or participated in extensive fieldwork in the proposed field area. This project will be based out of the Yellowstone Bighorn Research Association, which is commonly used by geology field camps working in the area. Students will stay in group cabins, all three meals are provided, and there are several classrooms available for working on projects, lectures, and group discussions in the evenings. Collected fossils will eventually be accessioned at the University of Michigan Museum of Paleontology under the Bureau of Land Management permits. An Isomet slow-speed saw, Buehler sander/grinder, electronic balance, and small vacuum chamber will be used to set up a histology lab in the field. Students will be trained in taking specimen photos, molding, and casting to preserve the morphology of the bones before sampling. Students will take mid-shaft cross sections of long bones and cross-sections of tooth roots using diamond blades on a slow-speed Isomet saw. Petrographic-style thin sections will be created according to standard paleohistological techniques (Lamm and Padian, 2013). A microscope with a USB-attached camera will be made available so that students can take photomicrographs of growth rings in bones and teeth. Students will use either personal laptops or laptops from one of the Project Directors’ institutions. Students working on floodplain or stratigraphic projects will be trained in sedimentologic analysis and measuring stratigraphic sections.

Safety
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 risk of cuts and scrapes when making thin sections. 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, 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 20 field seasons of experience working in the region. They have published several scientific articles centering on the field area. All have led several field crews of undergraduate and graduate students under similar circumstances.

PROFESSIONAL DEVELOPMENT

All students involved with the project will attend the GSA Cordilleran section meeting in Pasadena, California (12–14 May 2020). We hope most students will be first author on one abstract, 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 2020 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, 2020, 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.

References

Abels, H.A., Clyde, W.C., Gingerich, P.D., Hilgen, F.J., Fricke, H.C., Bowen, G.J., and Lourens, L.J. 2012. Terrestrial carbon isotope excursions and biotic change during Palaeogene hyperthermals. Nature Geoscience 5: 326–329.

Barnosky, A.D., Hadly, E.A., Gonzalez, P., Head, J., Polly, P.D., Lawing, A.M. et al. 2017 Merging paleobiology with conservation biology to guide the future of terrestrial ecosystems. Science 355: eaah4787.

D’Ambrosia, A.R., Clyde, W.C., Fricke, P.D. Gingerich, and Abels, H.A. 2017. Repetitive mammalian dwarfing during ancient greenhouse warming events. Science Advances 3: e1601430.

Bown, T.M., and Kraus, M.J. 1981. Lower Eocene alluvial paleosols Willwood Formation, northwest Wyoming, USA and their significance for paleoecology paleoclimatology, and basin analysis. Palaeogeography, Palaeoclimatology, Palaeoecology 34: 1–30.

Fricke, H.C., Clyde, W.C., O’Neil, J.R., and Gingerich, P.D. 1998. Evidence for rapid climate change in North America during the latest Paleocene thermal maximum: oxygen isotope compositions of biogenic phosphate from the Bighorn Basin (Wyoming). Earth and Planetary Science Letters 160: 193–208

Gingerich, P.D. 2003. Mammalian responses to climate change at the Paleocene-Eocene boundary: Polecat Bench record in the northern Bighorn Basin, Wyoming. In S.L. Wing, P.D. Gingerich, B. Schmitz, and E. Thomas (eds.), Causes and consequences of globally warm climates in the early Paleogene, Geological Society of America, Special Paper 369: 463–478.

Palkovacs, E.P. 2003. Explaining adaptive shifts in body size on islands: A life history approach. Oikos, 103: 37–44.

Secord, R., Bloch, J.I., Chester, S.G.B., Boyer, D.M., Wood, A.R., Wing, S.L., Kraus, M.J.,McInerney, F.A., and Krigbaum, J. 2012. Evolution of the earliest horses driven by climate change in the Paleocene-Eocene Thermal Maximum. Science 335: 959–962.

Simons, E.L. 1960. The Paleocene Pantodonta. Transactions of the American Philosophical Society 50: 1–81.

Uhen, M.D., and Gingerich, P.D. 1995. Evolution of Coryphodon (Mammalia, Pantodonta) in the late Paleocene and early Eocene of northwestern Wyoming. Contributions from the Museum of Paleontology, University of Michigan 29: 259–289.

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

Zachos, J.C., Dickens, G.R., and Zeebe, R.E. 2008. An early Cenozoic perspective on greenhouse warming and carbon-cycle dynamics. Nature 451: 279–283.

Rhyolitic eruptions

Rhyolitic eruptions

Using 3D petrography of microlites and bubbles in obsidian to assess factors governing eruptive style for rhyolitic magmas

Overview: This four-student advanced Keck project will investigate the factors controlling eruption style in rhyolite volcanic systems, which are among the largest and most destructive on Earth. The project will kick off with a visit to the spectacular Long Valley caldera in central-eastern California to begin building our understanding of rhyolitic systems and to sample young lava domes of the Inyo and Mono craters volcanic chains. Relocating to San Antonio we will then embark on a 3D micro-textural and in-situ analytical study of flow-banded obsidian from Long Valley and from heavily dissected and deeply exposed rhyolite lavas, pyroclastic deposits, and associated vent structures from the largest volcano in eastern Australia. Students will use: (1) bubble and microlite size, shape, number, and orientation distributions to constrain magma ascent and eruption dynamics; and (2) mineral and glass major-element and volatile concentrations to reconstruct pre-eruptive magma storage conditions and to track potential changes in magma properties and compositions during eruption.

Aerial photo of the lava domes and coulées of the Mono-Inyo craters volcanic chain, looking south from Mono lake towards Long Valley caldera and Sierra Nevada mountains (Photo by R. Von Huene, 1971, United States Geologic Survey)

When: June 15 – July 13, 2019 (tentative)

Where: Long Valley, California (introduction and field work) and San Antonio, Texas (lab work).

Who: Four rising senior students and project leader Dr. Kurt Knesel, Trinity University, [email protected]

Prerequisites and Recommended Courses: Students should have taken an Earth materials course, covering basic mineralogy & petrology. The ideal student would have also had (or would be taking during Fall 2019) a more advanced course in either igneous petrology or structural geology. Some background in chemistry and physics is also recommended but not required. We are particularly interested in applicants with an interest in volcanology, who are comfortable and enthusiastic about working in both outdoor and laboratory environments, 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 acquisition and analysis during the summer (approximately June 15 to July 13, 2019)
2. Follow-up data acquisition and analysis at home institution and regular correspondence with research team throughout the 2019-2020 academic year.
3. Write an abstract and present a paper (poster or talk) for either the Geological Society of America Cordilleran or Rocky Mountain section meeting in Pasadena, California (May 12-14), or Provo, Utah (May 4-5), respectively.
4. Write a short contribution (4-6 pages text + figures) to be published in the Proceedings of the Keck Geology Consortium 2020 Volume (first draft due Mid-February, 2020).
5. Expected but not required: Use this work for the completion of a senior thesis (or equivalent) at your home institution.

PROJECT DESCRIPTION

Background & Significance
Deciphering the factors governing eruption of intermediate to silicic magma is a fundamental problem in volcanology. A general model has emerged relating eruptive style to the interplay between ascent rate and the efficiency and extent of volatile loss during magma transport from subvolcanic chambers (e.g., Gonnermann & Manga, 2007). Fast ascent is believed to inhibit volatile loss, leading to volatile overpressure and ultimately explosive fragmentation; in contrast, slow magma ascent favors gas escape and lava extrusion. Rise-rate estimates for magmas of andesitic and dacitic compositions are indeed consistent with this model (e.g., Rutherford & Gardner, 2000). However, comparable data for rhyolitic eruptions is sparse (e.g., Costa & Dingwell, 2009; Pallister et al., 2013), and the extent to which ascent rate dictates degassing and eruptive behavior is unclear (e.g., Castro & Gardner, 2008).

Creative approaches to this critical problem are sorely needed. One promising avenue is quantitative 3-D petrographic study of the size, shape and orientation distributions of vesicles and microlites in flow-banded obsidian (i.e., rhyolitic volcanic glass with distinct bands typically defined by differences in abundance of microlites and/or bubbles). For example, orientations of dilute concentrations of microlites can be used to estimate the magnitude and type of shear strain accumulation during magmatic flow (e.g., Manga, 1998; Castro et al., 2002), while bubble shapes and orientations provide constraints on flow stresses and strain rates (e.g., Rust & Manga, 2002; Rust et al., 2003; Rust & Cashman, 2007). When combined, microlite and bubble measurements for the same samples provide a powerful tool for investigating the rates, timescales and dynamics of magma ascent and eruptive emplacement.

We have begun to apply this approach to highly dissected rhyolite domes, pyroclastic deposits, and associated feeder conduits of the compositionally bimodal Tweed volcano, in eastern Australia. Our initial measurements of microlite orientations (Figure 1) within the basal obsidian of a large lava dome yield simple-shear strains of up to 12 (Brown, 2010; Cook, 2011). Relative to an average pure-shear strain of 1 to 2 derived from fold geometries higher in the dome (Smith & Houston, 1994) and strains of < 5 for flow front and upper surface samples of other rhyolite domes (Castro et al., 2002; Befus et al., 2014; Befus et al., 2015), our estimates are remarkably high. Measured shapes and orientations of deformed bubbles (Figure 2) are also consistent with dominantly simple shear in the basal obsidian and allow calculation of shear rates on the order of 10-5s-1 (Knesel et al., 2011). Collectively, these results indicate that the basal portions of lava domes may accommodated most of the deformation during emplacement, while the main mass of lava is rafted above.

Figure 1: Example of 3D microlite reconstruction and strain estimates derived from variance in microlite alignment. (A) Scan of thin section of flow-banded obsidian showing location (yellow star) of area imaged in photomicrograph in (B). (B) photomicrograph of microlites in obsidian (scale bar is ~20 microns). (C) 3D microlite reconstruction derived from a stacked set of digitized images taken from sequential focal depths within the thin section. (D-F) Histograms showing trend direction for three reconstruction locations showing the range of estimated (simple shear) strain derived by comparison of variance in microlite orientation distributions to simulation of theoretical distributions obtained by integration of the relevant equations of motion (e.g., Manga, 1998) for three sample locations.

If microlite and bubble orientations mainly reflect flow at the surface, the average strain and strain rate for individual samples can be used to assess emplacement timescales. Our preliminary data indicate that some large lava domes (>1km3) may be emplaced over a period as brief as a few months, and fed by rhyolitic magma ascending at a rate potentially approaching 1m/s. This ascent estimate is unexpectedly fast and similar to pre-fragmentation rise-rate estimates for explosively erupted rhyolite at Chaitén volcano in Chile (Castro & Dingwell, 2009). If correct, it would appear that, contrary to conventional view, explosive rhyolitic volcanism may not be an inevitable consequence of rapid ascent alone. This possibility requires a re-assessment of current eruption models for rhyolitic systems.

Overarching Goal & Hypotheses
Our overarching goal is to better constrain the factors determining whether rhyolitic magma erupts explosively or effusively. Our starting hypothesis is that magma rise rate dictates the style of rhyolitic volcanism, with fast ascent leading to explosive eruption and slow ascent favoring effusive behavior (e.g., Gonnermann & Manga, 2007). However, as noted above, some of our preliminary results indicate that rapid rise of coherent (pre-fragmentation) rhyolitic magma may not necessarily lead to explosive eruption. An alternative hypothesis is that explosive fragmentation may result from sudden decompression of rhyolitic magma resident in a conduit prior to eruption, rather than simply by a fast-ascent mechanism (e.g., Castro & Gardner, 2008). In this second scenario, some Plinian and Sub-Plinian eruptions may be more akin to Vulcanian eruptions typical of intermediate magma compositions and may ultimately reflect the associated build up and alleviation of exsolved volatile pressure in the conduit transport system (e.g. Castro & Gardner, 2008).

Study Areas
The project includes examination of samples from two volcanic systems: the Mono-Inyo volcanic chain, Long Valley caldera (California), and rhyolite lavas and associated pyroclastic deposits of the Tweed volcano (Australia). The Tweed volcanic center has been the main research site for our structural analysis of flow-related textures over the past decade. The heavy dissection of this Miocene-age system provides us with unprecedented access to the basal glassy portion of rhyolite lava domes, as well as excellent exposure of cogenetic pyroclastic deposits and associated vent structures. In contrast, the Holocene Mono-Inyo chain in California provides easy access to the glassy upper and flow-front portions of rhyolite domes, and, due to its young age, is less susceptible to volatile redistribution following emplacement. Because we already have an extensive obsidian sample set for the Australian system (developed through the course of three honors theses at the University of Queensland), the field portion of the project will target the Mono-Inyo chain in California.

Research Methods
Field work: We will spend our first day or two in the field exploring key locations of fall and ash-flow deposits of the Bishop Tuff, along with key overlook stops of the spectacular Long Valley caldera, to develop an understanding of how field studies of volcanic rocks provide insight into eruptive dynamics. The remainder of our field time will be spent examining, documenting, and sampling macro-scale flow structures (e.g., orientations and dimensions of flow bands and folds) on the surfaces of young lava domes of the Inyo and Mono volcanic chains. The goal of this field work will be to assess the magnitude, type of strain developed, and displacement field in the outer portions of rhyolite lava domes, providing a comparative point to our investigation of the deeper portions of dissected domes in eastern Australia. As we explore the products of both effusive and explosive eruptions in the field, we will begin to formulate ideas for individual projects.

Quantitative and qualitative 3D micro-textural data: Up to this point my students and I have measured microlite and bubble populations using oriented thin sections and standard research-grade microscopes (Brown, 2010; Cook, 2011; Luck, 2012). The transparent nature of obsidian (Figure 1) allows 3D microlite orientations to be constrained using a series of high-magnification digital micrographs taken serially through different focal depths (i.e., focusing down into the thin section) followed by stacking and digitizing of these serial images in a computer-automated drafting (CAD) program (e.g., Manga, 1998). Quantification of bubble populations, which typically display a larger range in sizes compared to microlite populations, requires examination of two thin sections in mutually perpendicular planes (Figure 2) for each sample to enable the measurement of the three radii of deformed bubbles and the angle between the long dimension of bubbles and the flow direction, as defined by flow bands (e.g., Rust et al., 2003).

We will build on our quantitative textural dataset through use of the High-Resolution X-ray Computed Tomography (X-rayCT) facility at the University of Texas (UT) at Austin. The UT X-rayCT lab is a NSF-supported national shared multi-user facility, and is well set up to facilitate post-analysis image processing and visualization of scan data. The majority of our samples will likely be analyzed using the Xradia microXCT scanner, which has a resolution below 1 micrometer, but larger samples will take advantage of the upgraded North Star Imaging (NTS) scanner.

Microlite size distributions and number densities are byproducts of the 3D textural measurements discussed above. These size and density distributions can provide additional constraints on magma degassing and ascent dynamics (e.g., Toramaru et al., 2008; Melnik et al., 2011), but their application requires careful mineral identification. Towards this end, we will begin to quantify microlite populations (feldspar, pyroxene, and Fe-oxides) using the energy-dispersive (EDS) capability of the JOEL JSM-6010LA SEM in the Center for Science and Innovation at Trinity; for students with SEM capabilities at their home institution, this microlite quantification can be continued during the academic year.

Melt and mineral compositional data: Estimates of pre-eruptive storage conditions are critical to assessing degassing during ascent and to estimating melt viscosity. Importantly, the latter is also required to derive strain rates from bubble deformation data. We will determine magma storage conditions (pressure, temperature, volatile content) through analysis of phenocrysts, matrix glass, and quartz-hosted glass inclusions. Major elements will be determined by electron microprobe (EMPA) at UT and/or students’ home institutions. Volatile contents will be measured by Fourier-Transform Infrared (FTIR) spectroscopy at UT and/or students’ home institutions.

Figure 2: Example of the use of bubble orientations in obsidian to estimate shear rates. (A) Photomicrograph oriented perpendicular to the shear plane (containing the shear direction) suitable for measuring the semi-principal axes l, b and the angle between l and the flow direction, as shown in (C). Scale bars in (A & B) are ~200 microns. (B) Photomicrograph in plane perpendicular to bubble lineation used to measure b and c. (D) Fit to b-c bubble axis data measured from orientation in (B) used to calculate c values for data in (A), which allows derivation of the radius for undeformed bubbles using equation in (C). (E) Fit to “small deformation” bubble data (Ca<1) used to derive Ca/a ratio and ultimately to calculate the strain rate from the expression for the capillary number (Ca).

Potential Student Projects: While we envision a wide range of potential projects, our hope is to foster a collaborative research environment where all students feel comfortable sharing and integrating their results and to work as a team to address our overriding goal. As we begin to define each project, on the bases of student interests and consideration of availability of analytical equipment at their home institutions, it will be important to consider the following questions:
• Do microlite (& bubble) alignment reflect flow in the vent, flow on the surface, or both?
• How fast is fast? What is the upper limit of flow velocities (in shallow conduits) separating effusive and explosive eruptions?
• Over what time scales are rhyolite lava domes emplaced?
• How does strain accumulate across lava domes and what role does strain localization play in dome emplacement?
• What is the origin of pyroclastic obsidian?
• How do microlite and bubble textures in obsidian vary between lava, pyroclast, and vent samples?
• To what extent do pre-eruptive magma conditions in the feeder system, as well as storage chambers, play in determining eruptive style?
• How and where does rhyolitic magma degas?

Any one or more of these research questions could form the basis of an individual student research project. Each student could be involved in the acquisition and integration of a range of data types (quantitative textural data, mineral/glass major-element data, glass water and CO2 contents, etc.) for one type of volcanic deposit/structure (i.e., dome vs. pyroclastic vs. vent obsidian). Alternatively, some projects could primarily focus on an individual technique (e.g., FTIR) and data type (e.g., volatile contents) and could include samples from one, two, or all three deposit/structure types. Although we don’t plan to strictly predefine individual projects at the onset of the summer program, five options are listed below to provide a starting point for discussion.

Project 1: Pre-eruptive storage conditions and eruption dynamics of rhyolite lava.
Project 2: Origin of pyroclastic obsidian and implications for pre-fragmentation magma ascent in explosive eruptions.
Project 3: Magma flow dynamics and degassing within an exposed rhyolite vent.
Project 4: Breaking magma: repeated fracturing and healing of melt and the localization of strain in the basal shear zone of a lava dome.
Project 5: Structural analysis of flow foliations and folds as indicators of rheology and 3D kinematics of lava-dome emplacement.

Ultimately, individual projects will be formulated based on both student interests and availability of analytical equipment (e.g., SEM, EMPA, FTIR) at their home institutions. However, all students will gain exposure to cutting-edge high-resolution imaging techniques (SEM & X-rayCT), as well as experience in basic field techniques. All students will learn to:
• Properly document field data, including notebook organization and field-sketching techniques and field-based photography;
• Map and sample structural features of lava domes and flows using standard field equipment;
• Observe and analyze both qualitative and quantitative petrographic information (obtained from traditional optical microscopy) in the context of a focused research project, including microlite and bubble size and orientation data, shear flow indicators (e.g., rotated phenocrysts), folding of flow bands, and brittle-ductile textures (Trinity and home institutions);
• Measure and analyze qualitative and semi-quantitative textural and chemical data using an SEM with EDS (Trinity and home institutions);
• Utilize state-of-the-art X-ray computed tomography (X-rayCT) techniques to obtain and visualize 3D textural data for volcanic samples (UT).

PROJECT LOGISTICS

The summer portion of the project will tentatively run from June 15 to July 13, and will involve a combination of field work (Long Valley, CA) and laboratory work (Trinity and University of Texas).

The first quarter of the project will be dedicated to field work at Long Valley caldera and the associated Inyo-Mono volcanic chain. Students will fly directly to LA, where we will meet at LAX, rent a vehicle, and drive to Bishop (about 5 hours driving time). While in the field we will plan to stay at the Owens Valley Station (OVS) of the White Mountain Research Station (WMRS). The OVS is located about 4 miles east of the town of Bishop at an elevation of 4108 ft; it has air-conditioned dorms and provides excellent cooked meals. We tentatively plan to drive back to LA on morning of June 24th and fly to San Antonio in the evening.

The remainder of the time in the summer will be spent working at Trinity and the University of Texas in Austin. Students will stay in dorms at Trinity with other summer research students. Most dorms have kitchens facilities, so meals can be prepared on campus. Given that our stay at Trinity will coincide with the summer academic session, there should also be access to the main dining facility on campus (Mabee Dining Hall).

Upon arrival at Trinity, we will follow up our field work with a 3-day short course meant to: (1) provide an overview of volcanism in eastern Australia and a hands-on introduction to the associated obsidian sample set, which will complement the samples we collected from the Mono-Inyo chain; (2) an overview of the analytical techniques that we will employ at Trinity, UT, and/or students’ home institutions; and (3) an introduction to the theoretical aspects of magma flow and deformation, including application of quantitative microlite and bubble data. During this stage, we will begin examining the macro and micro-textures of the obsidian samples (in hand-samples and in thin-sections), as we work to refine the individual student projects.

Once the projects are set, students (both individually and collectively) will concentrate on: (1) developing a research proposal, including a timeline for the academic year; (2) sample preparation (e.g., thin/thick-section billet preparation, carbon-coating existing thin-sections, cylinder coring for XrayCT); and (3) initial data acquisition and treatment (primarily SEM work at Trinity & XrayCT work at UT). The close proximity of Trinity and UT (~ 1-hour dive) should allow us to organize sample preparation, data acquisition and treatment, and initial data analysis as needed.

Once at their home institutions, students will continue data collection and analysis as set out in their research proposals. Monthly or, if necessary, bi-weekly Skype, Facetime and/or WhatsApp meetings will be organized with each student and their home advisor (when possible) and with all of the students as a group (when appropriate) to ensure we stay on track to meet our individual and collective goals.

Safety
As with any field and lab work there will be inherent safety concerns. Field hazards include dehydration, heat exhaustion, sunburn, insect bites, poisonous snakes, and physical injuries, such as sprained ankles, broken bones, and skin abrasions or lacerations, as well as potential personal injury due to vehicular accident during travel to and from the field area and daily trips to individual field sites. Lab risks for this project are relatively minor but do include possible skin lacerations or abrasion when cutting or coring samples for preparation of thin/thick section billets and for X-rayCT samples. Risks will be mitigated by adhering to proper safety protocols, including wearing appropriate protective equipment and following standard operating procedures, both in the field and in the lab. We will hold safety meetings where we identify hazards and assess risks, and outline appropriate control measures.

Although summertime high temperatures at the Owens Valley station (at an elevation of just over 4000 ft) are typically in the mid 90s, the majority of field sites in the Mono-Inyo craters area are between 7000 to 8000 ft, where summertime highs are typically 70-80ºF and average lows are in the low to mid 40s. Thus, layered clothing is necessary, and a medium-sized day pack is essential to allow for clothing changes and sufficient food and water (several large bottles) for each day. Sturdy hiking boots and gloves (ideally leather) are also key for safety while working on blocky lava flows and domes.

PROFESSIONAL DEVELOPMENT

Towards the end of the 2019-2020 academic year, we plan to take all participants to either the GSA Cordilleran (May 12-14) or Rocky Mountain (May 4-5) section meeting in Pasadena, CA, or Provo, Utah, respectively, to present their results. We hope that most students will be first author on one paper (poster or talk), and probably secondary authors on others due to the collaborative nature of the project. The project director will work with each student and their home advisor to facilitate this important step in their professional development. And, recognizing that the timing of GSA section meetings may present issues with exam and other class-project deadlines towards the end of the academic year, the project director will coordinate with each student and their home advisor to select the most appropriate meeting.

In addition, all students are required to complete a 4-6 page (short communication) that will be published in the Proceedings of the Keck Geology Consortium 2020 Volume (see examples from previous years). The first draft of this paper will be reviewed by your research advisor at your home institution in February, 2020, with the revised version sent to the project director by March 1. Final versions of your paper and figures will be submitted to the Keck Office in mid-March.

References

Befus, K.S., Zinke, R.W., Jordan, J.S., Manga, M., & Gardner, J.E. (2014) Pre-eruptive storage conditions and eruption dynamics of a small rhyolite dome: Douglas Knob, Yellowstone volcanic field, USA. Bulletin of Volcanology 76, 1-12.

Befus, K.S., Manga, M., Gardner, J.E., & Williams, M. (2015) Ascent and emplacement dynamics of obsidian lavas inferred from microlite textures. Bulletin of Volcanology 77, 1-17.

Brown, A. (2010) Flow dynamics, strain history and structural evolution of the basal shear zone of silicic lava, Minyon Falls Rhyolite, New South Wales, Australia. Unpublished Honors Thesis, University of Queensland, pp. 53.

Castro, J., Manga, M., & Cashman, K. (2002) Dynamics of obsidian flows inferred from microstructures: insights from microlite preferred orientations. Earth and Planetary Science Letters 302, 38-50.

Castro, J.M. & Gardner, J.E. (2008) Did magma ascent rate control the explosive-effusive transition at the Inyo volcanic chain, California? Geology 36, 279-282.

Castro, J.M. & Dingwell, D.B. (2009) Rapid ascent of rhyolite magma at Chaiten volcano, Chile. Nature 461, 780-784.

Cook, 2011 Ascent and emplacement history of silicic lava inferred from microlite and bubble shapes and orientations Minyon Falls Rhyolite, New South Wales, Australia, Unpublished Honors Thesis, University of Queensland, pp. 250.

Gonnermann, H.M. & Manga, M. (2007) The fluid mechanics inside a volcano. Annual Review of Fluid Mechanics 39, 321-356.

Knesel, K., Brown, A., Cook, S. & Luck, D. (2011) Strain history and emplacement dynamics of lava domes: insights into shear-fragmentation and degassing of silicic magma. Biennial Conference of the Geological Society of Australia Specialist Group in Geochemistry, Mineralogy & Petrology, Murramarang, Australia.

Luck, D. (2012) Flow dynamics and eruptive history of silicic magma from the Tweed shield volcano, using bubble deformation analysis. Unpublished Honors Thesis, University of Queensland, pp. 138.

Manga, M. (1998) Orientation distribution of microlites in obsidian. Journal of Volcanology and Geothermal Research 86, 107-115.

Melnik, O.E., Blundy, J.D., Rust, A.C. & Muir, D.D. (2011) Subvolcanic plumbing systems imaged through crystal size distributions. Geology 39, 403-406.

Pallister, J.S., Diefenbach, A.K., Burton, W.C., Munoz, J., Griswold, J.P., Lara, L.E., Lowenstern, J.B., & Valenzuela, C.E. (2013) The Chaiten rhyolite lava dome: Eruption sequence, lava dome volumes, rapid effusion rates and source of the rhyolite magma. Andean Geology 40, 277-294.

Rust, A.C., & Manga, M. (2002) Bubble shapes and orientations in low Re simple shear flow. Journal of Colloid and Interface Science 249, 476-480.

Rust, A.C., Manga, M. & Cashman, K.V. (2003) Determining flow type, shear rate and shear stress in magmas from bubble shapes and orientations. Journal of Volcanology and Geothermal Research 122, 111-132,

Rust, A.C. & Cashman, K.V. (2007) Multiple origins of obsidian pyroclasts and implications for changes in the dynamics of the 1300 B.P. eruption of Newberry Volcano, USA. Bulletin of Volcanology 69, 825-845.

Rutherford, M.J. & Gardner, J.E. (2000) Rates of magma ascent. In Encyclopedia of Volcanoes (Ed. Sigurdsson, H.) 207-217.

Smith, J.V. & Houston, E.C. (1994) Folds produced by gravity spreading of a banded rhyolite lava flow. Journal of Volcanology and Geothermal Research 63, 89-94.

Toramaru, A., Noguchi, S., Oyoshihara, S. & Tsune, A. (2008) MND (microlite number density) water exsolution rate meter. Journal of Volcanology and Geothermal Research 175, 156-167.

Yellowstone rivers

Yellowstone rivers

Unraveling the controls on channel form and geomorphic history in northern Yellowstone National Park, Wyoming

Overview: We will analyze the controls on fluvial processes and determine the geomorphic history of two streams in northern Yellowstone National Park. Documentation and analysis of the geomorphic history of streams in northern Yellowstone is essential for understanding how a trophic cascade caused by the removal and reintroduction of wolves may have altered stream behavior in the 20th century. To assess stream behavior during the historical period, it is necessary to quantify baseline natural stream variability during the Holocene. Along Blacktail Dear Creek, we will map terrace/floodplain landforms and measure channel geometry. The timing of sedimentation on terraces and floodplains will be studied using radiocarbon dating and short-lived radionuclides. On the Gallatin River, we will survey channel cross sections throughout the drainage basin to investigate hydraulic geometry and environmental controls on channel form.

Figure 1: Streams in the Northern Range provide key riparian habitat in the relatively dry lower elevations of Yellowstone National Park.

When: July 22 – August 24, 2019

Where: We will meet in Walla Walla, WA. From Walla Walla, we drive to Yellowstone National Park and spend three weeks performing field work. We will return to Walla Walla for 1 week of work in the lab. From Walla Walla, students will return to their home institutions.

Who: A team of 4 students and Dr. Lyman Persico, Whitman College ([email protected])

Prerequisites and Recommended Courses: A course in earth surface processes (geomorphology) and sedimentology will be most useful. Other useful courses include paleoclimatology, ecology, and any field-based classes. What is most important, however, is a passion for working out of doors and a willingness to tackle unpredictable problems that always present themselves while doing field work. Applicants should have an interest in interdisciplinary research at the intersection of geology and ecology. Applicants must be willing to spend long days collecting field data in one of the most beautiful places on Earth, and spend the evenings discussing fluvial geomorphology and camping. Students wanting to use this work for a senior thesis will have preference. Letters of reference should speak to the applicant’s ability to work independently and their potential for both field and laboratory research.

Expectations and Obligations:
1. Participation in all project-related work during the summer (July 22-Aug 24).
2. Data analyses at home institution and regular conference calls with the research team throughout the academic year.
3. Write an abstract and present a poster at the Rocky Mountain sectional meeting of the Geological Society of America in Utah Valley, UT (May 4-5 2020).
4. Expected but not required: Use the research for a senior thesis (or equivalent).

PROJECT DESCRIPTION

Introduction and Rationale
Riparian corridors are key ecological zones in semiarid regions, as they provide abundant water and food resources and are typically more biologically diverse than the overall landscape. These corridors are particularly important in the relatively dry Northern Range of Yellowstone National Park (Yellowstone National Park, 1997). The Northern Range is synonymous with the winter range of the northern Yellowstone Elk herd. The Northern Range (Fig. 1 and 2) is relatively dry (mean annual precipitation: 350-500 mm) and the low-elevation region is dominated by sagebrush-grasslands with scattered conifer groves. In the early 20th century, many streams in the Northern Range hosted abundant beaver and beaver dams (Warren, 1926). Beaver are considered a keystone species of riverine-riparian ecosystems (Naiman et al., 1988b) as beaver dams elevate water tables, expand riparian habitat, increase aquatic productivity, and store more groundwater (Naiman et al., 1986; Naiman et al., 1988a; Pollock et al., 1995; Gurnell, 1998; Anderson et al., 2006; Westbrook et al., 2006; Gribb, 2007; Cooke and Zack, 2008; Brzyski and Schulte, 2009; Green and Westbrook, 2009). Beaver dams also reduce stream velocity and induce sedimentation in channels and on floodplains (Butler and Malanson, 1995). It has been hypothesized that the long-term effect of beaver damming may substantially aggrade valley floors (Ruedemann and Schoonmaker, 1938; Ives, 1942). More recent research using radiocarbon dating, however, has shown that there are limits on the net aggradation of beaver damming to less than 3 meters (Persico and Meyer, 2009; Polvi and Wohl, 2012; Persico and Meyer, 2013).

Figure 2: Blacktail Deer Creek and the Gallatin River drain portions of the Washburn and Gallatin ranges, respectively. The proposed study will focus on lower elevation stream reaches that receive less snow and are considered elk winter range.

Figure 3: The Northern Range stream of Elk Creek contained many beaver dams in the 1920s that extended across much of the valley floor. Those beaver dams were abandoned by the 1920s and the stream has incised over 2 m from the top of the beaver bond sediments.

Interestingly, beaver have been largely absent from the Northern Range since the mid-20th century (Fig. 3, Jonas, 1955). The causes of beaver decline and associated riparian zone changes have been debated in both the scientific literature and popular press over the past three decades (Yellowstone National Park, 1997; National Research Council, 2002). It has been proposed that Northern Range streams experienced an ecosystem state switch from beaver-willow to elk-grasslands during the latter half of the 20th century (Wolf et al., 2007). According to some, the loss of beaver is the direct result of competition from elk (Chadde and Kay, 1991). Elk populations increased dramatically in the 20th century due to the extirpation of wolves by hunting. Large elk populations have led to over-browsing of willow and other riparian vegetation. Mature aspen and riparian tall-willow stands, important food resources for beaver, have declined since park establishment, but aspen were never abundant in historic or Holocene time (Houston, 1982; Whitlock and Bartlein, 1993; Romme et al., 1995).

The loss of beaver and elk browsing have potentially caused significant alterations to Northern Range streams. The loss of beaver dams have caused channels to incise and floodplain abandonment (Fig. 3, Wolf et al., 2007; Beschta and Ripple, 2018). Channel incision has also caused the lowering of water tables, which limits willow and aspen growth (Marshall et al., 2013). These changes serve to disconnect channels from floodplains thereby reducing riparian areas (Marshall et al., 2013), however preliminary results indicate that at least some stream incision in the Northern Range predates the historical period (Fig. 5, Persico and Meyer, 2009). Additionally, the decreased riparian vegetation has led to widespread degradation of stream and riparian habitat via channel widening by bank erosion (Chadde and Kay, 1991; Beschta and Ripple, 2006; Wolf et al., 2007).

Regardless of changes to vegetation structure in Northern Range riparian communities, there are other factors that control channel form and stream dynamics including flow properties, bank material, subsurface conditions, and climatic variability (Knighton, 1998). In the greater Yellowstone ecosystem, climate variability is a significant factor in the long-term history of channel dynamics (Meyer, 2001; Persico and Meyer, 2009, 2013). Channel response to forest-fire related sedimentation is another important control on channel morphology in YNP (Meyer et al., 1992; Meyer et al., 1995; Legleiter et al., 2003). Although there is abundant research on the ecological dynamics of the Northern Range, relatively little research has focused on the stream channel and valley floor itself (Fig. 4). For example, there is little research that has attempted to differentiate terrace and floodplain deposits using geochronologic methods. Both Blacktail Deer Creek and the Gallatin River are sites where there is much discussion of the impacts of trophic cascades on channel dynamics (Beschta and Ripple, 2006; Beschta and Ripple, 2018). The proposed research is an important contribution to the study of the magnitude and extent of the effects of trophic cascades, which has even made it to the popular press in recent years (Robbins, 2005; Chadwick, 2010).

Figure 4: Blacktail Deer Creek drains the northern flanks of the Washburn Range. The stream has an inset floodplain. It is not clear how much of the valley floor is a Holocene terrace or historical floodplain that has been more recently abandoned.

Figure 5: On the east fork of Blacktail Deer Creek a sediments in a terrace ~1.5 above the modern floodplain accumulated 7-3 ka and incision commenced ~1.5 ka (Persico and Meyer, 2009). It is unknown how widespread this surface is or its relationship to the historical floodplain proposed by Bescthta and Ripple (2018).

Proposed Research: The primary goal of this project is to determine the environmental controls on channel form and fluvial dynamics on two streams in northern Yellowstone. This work will expand on the previous research on channel forms in Yellowstone (e.g. Meyer et al., 1995; Meyer, 2001; Legleiter et al., 2003; Persico and Meyer, 2009) and focus on detailed measurements of valley floor and channel morphology. The primary goal will be accomplished through mapping of terrace/floodplain surfaces, characterizing terrace/floodplain deposits, and estimation of the timing of floodplain/terrace aggradation.

On Blacktail Deer Creek, we will combine high-resolution RTK GPS measurements with geomorphic mapping to produce surficial geologic maps of terrace and floodplain surfaces (Fig. 4). On Blacktail Deer Creek glacial erosion and modification of topography has resulted in diverse fluvial valley widths and gradients, so that very gentle to steep channels exist across the entire range of contributing basin areas. Thus, the relationship between hydrologic and geomorphic controls and channel morphology can be fully examined. The stratigraphy and soil development in terrace deposits will be described in detail. Sediment samples will be collected from the sediments for laboratory analyses of grain size and organic content. Charcoal and wood fragments will be collected for 14C dating. The youngest ages of organic material that can be dated using 14C is 1950 due to above ground nuclear testing that has “spiked” the amount of 14C in the atmosphere since that time. Additionally, significant variability of atmospheric14C in the past 100-200 years has created a radiocarbon plateau, which produces significant errors when calibrating these young ages (Fig. 7). We will supplement the timing of sediment deposition via14C with short-lived radionuclides (Goldberg and Koide, 1962; Krishnaswami et al., 1980). We will collect sediment samples and estimate concentrations of atmospherically-derived 137CS and 210Pb in both terrace and floodplain sediments. These analyses allow for a more detailed analysis of sedimentation rates in the past several hundred years (Whiting et al., 2005; Soster et al., 2007).

On the Gallatin River, the goal of the proposed research is to characterize downstream changes to the geometry of the active channel. The Gallatin River drains the western flank of the Gallatin Range. The upper reaches of the river are outside of elk winter range providing a control for streams in northern Yellowstone that have not been influenced by elk overbrowsing. A series of cross sections will be measured by RTK GPS and supplemented by a total station when necessary. The geometry of channels will be combined with surficial and geologic maps to determine geologic controls on channel forms, which can be compared to environmental controls such as elk browsing. In the lab, cross sections will be used to estimate the hydraulics of floods along the river using HEC-RAS modeling.

Potential Student Projects
Project 1: Mapping of channel, floodplain, and terrace landforms along Blacktail Deer Creek. This student project will use a combination of survey data and surficial geologic mapping to produce a highly detailed map of fluvial landforms along the valley floor. Features will be mapped with <0.25m vertical precision using both an RTK GPS and total station. Coring analysis of up to 18 trees located on terrace surfaces will help to constrain the age of the floodplain and terrace surfaces. In the lab the student will use ARCGIS to analyze the magnitude of incision and percentage of the valley floor that is comprised of the different surfaces.

Project 2: Characterization of floodplain/terrace sediments and estimation of the timing of deposition by radiocarbon dating. This student project will focus on the deposit of terraces and floodplains. Field activities will include recording detailed stratigraphic and soil horizon observations and sampling the sediments and organic material preserved in the sediments (Fig 6). Estimation of the timing of deposition of terrace surfaces will be made by dating charcoal and wood preserved in overbank deposits. Laboratory activities at Whitman College will include using the laser diffractometer to measure sediment sizes, identifying wood type, and preparing samples of modern root samples to send to Direct AMS for14C analyses. I will work with the student and the home advisor for analysis of the ages in including calibration.

Project 3: Characterization of floodplain/terrace sediments and estimation of the timing of deposition by short-lived radionuclides. This student project will focus on the same terrace and floodplain stratigraphy of Project 2. The use of the short-lived radionuclides 147Cs and 210Pb will be used to determine terrace and floodplain stability. Field activities include recording detailed stratigraphic and soil horizon observations and sampling the sediments and organic material preserved in the sediments. Sediment samples will be collected from locations where multiple terrace and floodplain surfaces are present. Short cores will be collected using a push corer. Laboratory activities at Whitman College will consist of measuring the organic content of sediments using Loss on Ignition (LOI) and processing the cores by subsampling each core at 5 cm intervals. These sub samples will be sent to Oberlin College for determination of 210Pb and147Cs concentrations. The student will work with me, and Amanda Schmidt at Oberlin on analyzing the isotope data.

Project 4: Measuring downstream changes in hydraulic geometry of the Gallatin River. This student project will focus on characterizing the hydraulic geometry of the Gallatin River. Field activities will include collecting a series of cross sections in and above elk winter range. This student project will analyze a series of cross sections. Laboratory activities include developing a simple 2D hydraulic model using HEC-RAS. This model will allow the student to assess where there has been recent incision of the channel.

Figure 6: Terrace deposit on Blacktail Deer Creek with abundant woody material for 14C dating. The stratigraphy and soil development will be described in the field. Samples will be collected for 14C, organic content, and grain size analyses.

Figure 7: Calibration age of a hypothetical 14C age of 150 years. Due to a radiocarbon plateau, this simple has high probability of any time in the past 300 years.

PROJECT LOGISTICS

Students will arrive in Walla Walla on July 22. We will spend two nights on Whitman Campus. We will prepare for the field work in the science building on July 23 and leave for Yellowstone on July 24. While in Yellowstone we will first stay north of the Park, near Gardiner, MT. We will likely camp at the Eagle Creek campground, although, the campground is first-come-first-serve, so the backup plan is to stay at the Jardine campground, which is more remote and not as likely to fill up. We will stay at Eagle Creek for 14 nights while performing all field work on Blacktail Dear Creek. Most meals will be prepared at the campsite on camp stoves borrowed from the Whitman College. We will resupply and do laundry in the town of Gardiner. For field work on the Gallatin River we will most likely stay at the Rainbow Point campground on Hebgen Lake.

Students will need to be able to carry a medium-sized field pack and field equipment every day. We will also pack water and lunch each day. We will be hiking up to six miles per day. Most of the hiking will be on the valley floor, thus relatively low gradients. We will also be surveying stream cross sections. This will require multiple river crossings.

Research Schedule:

Phase 1 (7/22-7/25) Travel and Introduction

  • Arrive in Walla Walla
  • Crash course in methods of fluvial geomorphology
  • Risk assessment and mitigation discussion
  • Pack
  • Travel to Yellowstone

Phase 2 (7/26-8/9) Blacktail Deer Plateau Field Work

  • Mapping and survey of terrace and floodplain surfaces
  • Terrace deposit stratigraphic descriptions and sampling for radiocarbon
  • Sediment Core sampling for short-lived radionuclides

Phase 3 (8/10-8/19) Gallatin River Field Work and Travel

  • Mapping and survey of terrace and floodplain surfaces
  • Drive to Walla Walla

Phase 4 (8/20-8/24) Laboratory Analyses

  • Prepare and ship wood/charcoal samples for radiocarbon analyses
  • Prepare and ship sediment samples for short-lived radionuclide analyses
  • Begin analyses of cross section and mapping data

Phase 5 (4-5 May 2020) Professional Development

  • Poster presentations at Rocky Mountain GSA

Safety:
There are risks inherent to field research. These risks include physical injuries such as broken bones and sprained ankles. Other risks include venomous snakes, dehydration, heat stroke, sunburn, and mosquito bites. These risks will be mitigated by following proper field and wilderness protocols. Professor Persico has extensive field and wilderness experience as a field camp instructor and outdoor recreation trip leader. Professor Persico will hold a safety meeting in Walla Walla to explain the risks and the strategies that will be employed to mitigate these risks. Another risk in Yellowstone are bears. Professor Persico has 10 seasons of field experience with Yellowstone bears. Bear spray is the standard bear deterrent in YNP. We will be working mostly at low elevations, where black bears are more common (Grizzly bears claim the higher elevations farther away from humans during the summer). Black bears are less of a hazard compared to Grizzly Bears (much less aggressive). Professor Persico will talk about bear safety before the field work. This will include watching a You Tube video of the proper procedure for using bear spray. Each member of the team will have a can of bear spray. Additionally, while in the field I will use the time-honored tradition of banging one’s shovel against rocks when hiking.

PROFESSIONAL DEVELOPMENT

Professor Persico will take all participants to the Rocky Mountain section meeting of the Geological Society of America in Utah Valley, Utah (4-5 May 2020). Each student will prepare their own first-authored abstract with the other students as collaborators.
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.

References

Anderson, C.B., Griffith, C.R., Rosemond, A.D., Rozzi, R., Dollenz, O., 2006. The effects of invasive North American beavers on riparian plant communities in Cape Horn, Chile – Do exotic beavers engineer differently in sub-Antarctic ecosystems? Biological Conservation 128, 467-474.

Beschta, R.L., Ripple, W.J., 2006. River channel dynamics following extirpation of wolves in northwestern Yellowstone National Park, USA. Earth Surface Processes and Landforms 31, 1525-1539.

Beschta, R.L., Ripple, W.J., 2018. Can large carnivores change streams via a trophic cascade? Ecohydrology 0, e2048.

Brzyski, J.R., Schulte, B.A., 2009. Beaver (Castor canadensis) Impacts on Herbaceous and Woody Vegetation in Southeastern Georgia. American Midland Naturalist 162, 74-86.

Butler, D.R., Malanson, G.P., 1995. Sedimentation rates and patterns in beaver ponds in a mountain environment. Geomorpholo 13, 255-269.

Chadde, S.W., Kay, C.E., 1991. Tall-willow communities on Yellowstone’s Northern Range: A test of the “natural-regulation” paradigm, in: Keiter, R.B., Boyce, M.S. (Eds.), The Greater Yellowstone Ecosystem. Yale University Press, Binghamton, pp. 231-263.

Chadwick, D.H., 2010. Wolf Wars, National Geographic.

Cooke, H.A., Zack, S., 2008. Influence of beaver dam density on riparian areas and riparian birds in shrubsteppe of Wyoming. Western North American Naturalist 68, 365-373.

Goldberg, E.D., Koide, M., 1962. Geochronological studies of deep sea sediments by the ionium/thorium method. Goeochemica Cosmochemica Acta 26, 417-450.

Green, K.C., Westbrook, C.J., 2009. Changes in riparian area structure, channel hydraulics, and sediment yield following loss of beaver dams. Journal of Ecosystems and Management 10, 68-79.

Gribb, W., 2007. Beaver (Castor canadensis) impacts and characteristics on stream hydrology and vegetation in the Snake River Drainage System, Grand Teton National Park, Wyoming. United States Department of the Interior, Report on file, National Park Service, Moose WY.

Gurnell, A., 1998. The hydrogeomorphological effects of beaver dam-building activity. Prog. Phys. Geogr. 22, 167-189.

Houston, D.B., 1982. The northern Yellowstone elk. Macmillian, New York, NY.

Ives, R., 1942. The beaver-meadow complex. Journal of Geomorphology 5, 191-203.

Jonas, R.J., 1955. A population and ecological study of the beaver (Castor canadensis) of Yellowstone National Park. University of Idaho, p. 193.

Knighton, D., 1998. Fluvial Forms and Processes A New Perspective. Oxford University Press, New York.

Krishnaswami, S., Benninger, L.K., Aller, R.C., Von, Damm, K.L., 1980. Atmospherically derived radionuclides as tracers of sediment mixing and accumulation in near-shore marine and lake sediments—Evidence from 7Be, 210Pb, and 239,240Pu. Earth and Planetary Science Letters 47, 307–318.

Legleiter, C., Lawrence, R., Fonstad, M., Marcus, W., Aspinall, R., 2003. Fluvial response a decade after wildfire in the northern Yellowstone ecosystem: a spatially explicit analysis. Geomorpholo 54, 119-136.

Marshall, K.N., Hobbs, N.T., Cooper, D.J., 2013. Stream hydrology limits recovery of riparian ecosystems after wolf reintroduction. Proceedings of the Royal Society B-Biological Sciences 280.

Meyer, G.A., 2001. Recent large-magnitude floods and their impact on valley-floor environments of northeastern Yellowstone. Geomorpholo 40, 271-290.

Meyer, G.A., Wells, S.G., Balling, R.C., Jull, A.J.T., 1992. Response of alluvial systems to fire and climate change in Yellowstone-National-Park. Nature 357, 147.

Meyer, G.A., Wells, S.G., Jull, A.J.T., 1995. Fire and alluvial chronology in Yellowstone National Park: Climatic and intrinsic controls on Holocene geomorphic processes. Geological Society of America Bulletin 107, 1211-1230.

Naiman, R.J., Johnston, C.A., Kelley, J.C., 1988a. Alteration of North-American streams by beaver. Bioscience 38, 753-762.

Naiman, R.J., Johnston, C.A., Kelly, J.C., 1988b. Alteration of North American streams by beaver. Bioscience 38, 753-762.

Naiman, R.J., Melillo, J.M., Hobbie, J.E., 1986. Ecosystem alteration of boreal forest streams by beaver (Castor-canadensis). Ecology 67, 1254-1269.

National Research Council, 2002. Ecological Dynamics on Yellowstone’s Northern Range. National Academy Press, Washington DC.

Persico, L., Meyer, G., 2009. Holocene beaver damming, fluvial geomorphology, and climate in Yellowstone National Park, Wyoming. Quaternary Res 71, 340-353.

Persico, L., Meyer, G., 2013. Natural and historical variability in fluvial processes, beaver activity, and climate in the Greater Yellowstone Ecosystem. Earth Surface Processes and Landforms 38, 728-750.

Pollock, M.M., Naiman, R.J., Erickson, C.A., Johnston, C.A., Paster, J., Pinay, G., 1995. Beaver as engineers: influences of biotic and abiotic characteristics of drainage basins, in: Jones, C.G., Lawton, J.H. (Eds.), Linking species and ecosystems. Chapman and Hall, New York, pp. 117-126.

Polvi, L.E., Wohl, E., 2012. The beaver meadow complex revisited – the role of beavers in post-glacial floodplain development. Earth Surface Processes and Landforms 37, 332-346.

Robbins, J., 2005. Hunting Habits of Wolves Change Ecological Balance in Yellowstone, New York Times, New York, NY.

Romme, W.H., Turner, M.G., Wallace, L.L., Walker, J.S., 1995. Aspen, elk, and fire in northern Yellowstone National Park. Ecology 76, 2097-2106.

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