Title

History of Groundwater Flow in the Southern Great Basin Inferred From Paleo-deposits

Poster Number

21A

Lead Author Major

Geological and Environmental Science, Conc. Geology

Lead Author Status

Senior

Format

Poster Presentation

Faculty Mentor Name

Laura K. Rademacher

Faculty Mentor Email

lrademacher@PACIFIC.EDU

Faculty Mentor Department

Geological and Environmental Science

Additional Faculty Mentor Name

Yadira Ibarra

Additional Faculty Mentor Email

yibarra@sfsu.edu

Additional Faculty Mentor Department

Department of Earth & Climate Sciences, San Francisco State University

Additional Faculty Mentor Name

Marty D. Frisbee

Additional Faculty Mentor Email

mdfrisbee@purdue.edu

Additional Faculty Mentor Department

Department of Earth, Atmospheric, and Planetary Sciences, Purdue University

Graduate Student Mentor Name

Zachary P. Meyers

Graduate Student Mentor Email

meyersz@purdue.edu

Graduate Student Mentor Department

Department of Earth, Atmospheric, and Planetary Sciences, Purdue University

Abstract/Artist Statement

Paleohydrologic deposits (“spring mounds”) from the Great Basin were analyzed for petrographic indicators of past changes in groundwater flow throughout the groundwater system. This pilot study focuses on car­bonate samples collected from spring mounds in Death Valley National Park (DVNP), CA and Ash Meadows National Wildlife Refuge (AMNWR), NV. The sampled springs that host these carbonate deposits are part of a larger project investigating the relationship between groundwater flow and ecological diversity in the modern environment. This study seeks to understand how and why portions of the flow system have dried over time, while others remain active. Results from our investigation provides insight into how the Basin and Range spring systems have evolved through changing climate regimes.

Hand samples were collected from two sites: one site in eastern DVNP and one site in north-east AMNWR. Sampling locations were located in the distal, non-flowing regions of large modern springs. In the lab, samples were photographed at high resolution and then cut and polished into standard thin sections for petrographic analysis. Petrographic analyses on all samples revealed that they are largely calcium carbonate. However, the analyzed samples vary in crystal size from micrite layers to bands of bladed spar crystals that may represent seasonal changes in temperature during deposition. Several samples appear to have undergone diagenetic changes while others exhibit only minimal post-depositional changes.

Future work will include carbon and oxygen isotope analysis that may suggest paleoenvironmental changes, that coupled with the petrographic analysis, will provide insight into particular paleo-climate conditions that may have correlated with a change in crystal structure or periods of growth or non-growth in the carbonates, thus providing insight into flow histories. In addition, future luminescence dating of the cores to provide a timeline for these observed changes.

Location

DeRosa University Center Ballroom

Start Date

27-4-2018 12:30 PM

End Date

27-4-2018 2:30 PM

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Apr 27th, 12:30 PM Apr 27th, 2:30 PM

History of Groundwater Flow in the Southern Great Basin Inferred From Paleo-deposits

DeRosa University Center Ballroom

Paleohydrologic deposits (“spring mounds”) from the Great Basin were analyzed for petrographic indicators of past changes in groundwater flow throughout the groundwater system. This pilot study focuses on car­bonate samples collected from spring mounds in Death Valley National Park (DVNP), CA and Ash Meadows National Wildlife Refuge (AMNWR), NV. The sampled springs that host these carbonate deposits are part of a larger project investigating the relationship between groundwater flow and ecological diversity in the modern environment. This study seeks to understand how and why portions of the flow system have dried over time, while others remain active. Results from our investigation provides insight into how the Basin and Range spring systems have evolved through changing climate regimes.

Hand samples were collected from two sites: one site in eastern DVNP and one site in north-east AMNWR. Sampling locations were located in the distal, non-flowing regions of large modern springs. In the lab, samples were photographed at high resolution and then cut and polished into standard thin sections for petrographic analysis. Petrographic analyses on all samples revealed that they are largely calcium carbonate. However, the analyzed samples vary in crystal size from micrite layers to bands of bladed spar crystals that may represent seasonal changes in temperature during deposition. Several samples appear to have undergone diagenetic changes while others exhibit only minimal post-depositional changes.

Future work will include carbon and oxygen isotope analysis that may suggest paleoenvironmental changes, that coupled with the petrographic analysis, will provide insight into particular paleo-climate conditions that may have correlated with a change in crystal structure or periods of growth or non-growth in the carbonates, thus providing insight into flow histories. In addition, future luminescence dating of the cores to provide a timeline for these observed changes.