April 2023 Virtual Meeting

Monday, April 10, 2023
6:00 - 7:30 pm

Note: ETGS members will receive an email with info for logging into the meeting.

Award Winning Student Presentations

Evaluating Bulk δ13C and δ15N Values of Acidic Hydrothermal Sediments on Earth -- Implications for Mars Astrobiology



Chance Sturrup
Department of Earth and Planetary Sciences
University of Tennessee, Knoxville
M.S. Candidate


Stable carbon isotopes (δ13C) are often used as biosignatures in terrestrial samples on Earth. Similarly, the NASA Curiosity rover is capable of performing bulk in-situ δ13C analysis to search for biosignatures on Mars. However, there is a substantial knowledge gap pertaining to what types of isotopic signatures can be detected using bulk methods, specifically in acidic hydrothermal settings which may have once held microbial life on Mars. This research aims to address this knowledge gap by constraining the types of biosignatures detectable by bulk analysis in Mars-analog hydrothermal environments. Here, a total of sixty samples were collected from six hydrothermal sites across the United States and Iceland and subjected to δ13C analysis mimicking the capabilities of the Curiosity Rover. Analysis found that in the most analogous sites the presence of thermophilic microbes could be distinguished from inorganic carbon with bulk methods. This indicates that in-situ bulk δ13C analysis on Mars would be capable of identifying microbial isotope signatures in similar environmental conditions.


Chance is a second-year master's student working with Dr. Anna Szynkiewicz at the University of Tennessee Knoxville. He was born and raised in Fort Lauderdale and received his B.S. in Geology from the University of Florida in 2021. His graduate research focusses on stable isotope geochemistry in hydrothermal systems on Earth and their applications to on-going analysis on Mars. He presented his research in a talk at the 2023 Lunar and Planetary Science conference and is set to defend his master's thesis in early April of 2023.


A food web analysis for the subterranean fauna in the Croatian Dinaric Karst using stable isotopes


Hannah R. Rigoni
Department of Earth and Planetary Sciences
University of Tennessee, Knoxville
Ph.D. Candidate


Caves of the Dinaric karst are a hotspot for subterranean biology. Despite the long history of research covering various biological questions about the subterranean fauna in the region, we know little about how the animals interact with the food web. We used stable carbon and nitrogen isotopes to evaluate potential carbon sources and identify trophic levels of co-existing filter-feeders and motile stygobionts in three caves in Croatia. Stable carbon isotope values of dissolved organic carbon inside the caves and from surface water averaged -24.7 +- 2.2o/oo, dissolved inorganic carbon averaged -6.4+- 2.9o/oo, surface invertebrates averaged -26.1 +- 4.6o/oo, and cave filter feeders averaged -31.9 +- 1.7o/oo. Nitrogen isotope values revealed the potential for two trophic levels, with the shrimp, Troglocaris anophthalmus, occupying the omnivore niche in the cave ecosystems. These differences indicate that isotopically light carbon, potentially from chemolithoautotrophy could be supporting the filter-feeders near the base of the food web. This preliminary ecological assessment provides important information about nutrient cycling and food web structure, which will benefit conservation efforts to protect the cave and endemic fauna.


Hannah is a PhD student at the University of Tennessee studying carbon and nitrogen cycling in karst aquifers. She received her B.S. in Geology in 2017 from New Mexico Tech, where she focused on economic geology before finding her passion for biogeochemistry. Hannah worked as a biologist with the USGS in Boulder, Colorado Water Resources Mission Area for a year before returning to school.




Holocene Paleofloods Recorded in Floodplain Soil Profiles in the Upper Tennessee River Basin


Paula J. Perilla-Castillo, Sally. P Horn, Steven G. Driese, Tammy Rittenour, & Larry D. McKay
Department of Earth and Planetary Sciences
University of Tennessee, Knoxville
Ph.D. Candidate


Five sites exposed along the floodplain of the upper Tennessee River were examined to identify evidence of major Holocene flooding events. Sediments exposed in floodplains are not commonly used in paleoflood studies, but this investigation shows that they can provide valuable information in areas where no other records are available. Paleoflood records are present in the study area as deposits of coarser grain size sediments occurring within paleosol units. Sedimentological characterization was performed in paleosols and paleoflood sediments using particle-size analysis, magnetic susceptibility, organic matter content, and soil micromorphology. Geochemical characterization was performed with ex-situ portable X-ray fluorescence (pXRF). Stable carbon isotope analysis was performed to determine climate shifts registered in the paleosols. The paleoflood deposits are predominantly composed of fine-sand grain size minerals, with low organic matter content, and low magnetic susceptibility values. The paleosols are typically composed of silt- to very fine sand-grain size minerals, with higher organic matter content and higher magnetic susceptibility values. Results from pXRF indicate that the paleoflood deposits generally have lower concentrations of Al, Fe, K, Mn, Rb, and Ti than the paleosols. Concentrations of Si and Zr are higher for the paleoflood deposits, except where soil-forming processes have influenced the geochemical concentrations as is the case for a paleoflood deposit occurring as an E horizon. Radiocarbon and OSL (optically stimulated luminescence) ages reveal that the investigated profiles contain information on paleofloods between 8.6 and 0.2 ka B.P. The findings of this study agree with paleoenvironmental reconstructions from previous studies for the southeastern US and indicate the potential for using paleoflood deposits for paleohydrology studies and for reconstructing past fluvial activity where no other records are available.


Paula is a PhD student at the University of Tennessee in Geological and Earth Sciences/Geosciences, with a Master's degree in Groundwater from the University of Oklahoma, and Bachelor of Science from the Universidad Nacional de Colombia. Her experience and studies are varied including:

Saltwater injection related induced seismicity
Pore pressure diffusion
Groundwater studies and classical hydrogeology
Inventory of the Paleontological Collections
Creation of database for the Paleontological Collections
Knowledge of Specify Software for database creation
Hydrogeologist consultant
Elaboration of groundwater studies for land use planning
Geohazards consultancy for land use planning
Revision and assessment of mining investment projects in South America
Project proposals elaboration (In Spanish and English)
Interviewing of potential clients for mining investments and transactions
Elaboration of groundwater studies for oil/gas development projects and mining operations
Elaboration of saltwater injection reports to environmental authorities
GIS Knowledge


Greetings! We hope you will join us for the next ETGS virtual meeting, and that you, your family, and your colleagues are staying healthy and well. 

As a courtesy, please mute your cell phone or the microphone in your laptop/tablet to minimize background noise and feedback echoes. We will try to mute all participants until the presentation is finished. Please use the chat feature to type comments or questions during the presentation. We recommend that you send questions for the speaker to "everyone" so all participants can see the question. After the presentation, the speaker will answer questions.  During this Q&A period, you may unmute if you wish to ask a question verbally.

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Thank you for your patience and understanding as we continue adapting to this virtual format. As always, we welcome and appreciate your feedback and suggestions for improvement.


ETGS News:

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We look forward to seeing you at the next meeting.

ETGS is a volunteer organization. We need your help to continue serving those interested in the geology of East Tennessee and beyond. Please email us at
etgs@live.com if you would consider assisting in one of the following open positions. It is a great opportunity to expand your personal and professional network.

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Bob Gelinas



Page updated May 10, 2023