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Group Members

Postdoctoral Researchers

Dr. Natasha Sekhon (Website; IBES Profile) – Voss Postdoctoral Research Associate and Presidential Diversity Postdoctoral Fellow, 2021 to 2023

B.S. Earth System Sciences, University of California, Irvine, 2014; M.S. Geological Sciences, University of Texas, Austin, 2016; Ph.D. Geological Sciences, University of Texas, Austin, 2021

Natasha is a low-temperature geochemist and paleoclimatologist whose research combines concepts from karst and speleothem sciences to investigate the hydroclimate of terrestrial environments varying on seasonal to millennial time scales. She investigates the geochemical trends of stalagmites extracted from caves and actively monitors them to assess the sensitivity of climate variables on proxy systems. Her Ph.D. work explored the utility of stalagmites from near-entrance cave settings in New Mexico as potential recorders of recharge episodes. While at Brown, she will be working with the group studying the history of droughts and floods in the Philippines.


Dr. Evan Ramos (Website) – NSF EAR Postdoctoral Fellow, 2021 to 2023; Affiliate Postdoc 2023-2024

B.A. Geophysics and Planetary Sciences, Boston University, 2015; M.S. Geological Sciences, University of Texas at Austin, 2017; Ph.D. Geological Sciences, University of Texas at Austin, 2021

Evan is a geochemist whose research concerns the role of fluid-rock interactions in biogeochemical cycles, namely the carbon cycle. His M.S. research addressed fluid flow in hydrothermal environments and its influences on metamorphic decarbonation and, by extension, Phanerozoic climate. During his Ph.D., he studied the controls of silicate weathering by examining both modern and ancient surface environments with Li isotopes. At Brown and Rice University, where he is primarily appointed, he will research the coupling of the inorganic (i.e., silicate weathering) and organic carbon cycles by combining geochemical analyses of soils, river sediment, and river water with reactive transport models.



Piccione Headshot

Dr. Gavin Piccione ( – Postdoctoral Research Associate, 2023-Present

B.S. Geosciences (Summa cum Laude), Stony Brook University, 2016; Ph.D. Earth & Planetary Sciences, University of California Santa Cruz, 2023;

I am a geochemist and geochronologist with broad interests in the processes that link Earth’s climate and hydrosphere through time. My research leverages both traditional and novel terrestrial sedimentary archives to create time-resolved datasets that describe paleoclimate evolution on decadal to million-year timescales. I have applied these methods to reconstruct the rates of Antarctic ice sheet growth and retreat, and the impact of glaciers on global geochemical cycles. While at Brown, I am working with Dr. Daniel Ibarra on projects investigating the temporal variability of hydroclimate in the western US, as well as weathering beneath ice sheets. Before arriving at Brown, I earned my bachelor’s degree (with Honors) in Geoscience at Stony Brook University, and my PhD in Earth and Planetary Science at the University of California Santa Cruz.


Graduate Students

Catherine (Cathy) A. Gagnon (IBES Profile; LinkedIn) – DEEPS Ph.D. Candidate (4th year)

B.S. Geoscience (w/ hydrogeology concentration), The Pennsylvania State University, 2020

I came to Brown in Fall 2020 as a grad student interested in using stable isotope geochemistry methods to address questions related to past climate. My undergraduate work at Penn State involved constructing carbonate oxygen and carbon, and organic carbon isotope records of Holocene lake sediments near a Neolithic settlement in Dalmatia, Croatia. The work provided a climate context for an important time and location for the spread of early farming. My current project involves reconstructing the hydroclimate of Clayton Valley, NV from the late Pliocene to present using a combination of isotope measurements and lake balance modeling techniques. Through my work, I hope to improve future climate change projections for the western United States. In addition to research, I’m involved in k-12 earth science outreach through DEEPS STEP/DEEPS CORES. I currently reside in Providence with my little black cat.


Sebastian (Seb) Muñoz (IBES Profile) – DEEPS Ph.D. Candidate (3rd year) – Brown Presidential Fellow & NSF Graduate Research Fellow – co-advised by Larry Smith

B.S. Geological Sciences (hydrogeology honors) and B.A. Liberal Arts, University of Texas, Austin, 2018

Sebastian spends all of his time thinking about, studying, or boating on rivers. He is interested in how surface water chemistry will change in response to human activities and climate change. Previous work includes studying rock glaciers contributions to river flows in northern Chile, and understanding surface water and groundwater interactions downstream of a dam in the Colorado River near Austin, TX.


Theodore (Ted) Bobik (IBES Profile) – DEEPS Graduate Student (3rd year)

M.S. Earth and Environmental Science, Temple University

Theodore began his PhD at Brown University in Fall 2021 after completing his masters at Temple University, in his home city of Philadelphia, PA. The overarching theme of his research is to increase the efficacy and scope of paleosol-derived paleoclimate proxies by untangling authigenic and catchment-derived geochemical signals. In his work, he utilizes stable isotope analysis of authigenic clays and carbonates, trace elements, molecular weathering ratios, and multi-variable analysis of leaf wax n¬-alkanes to interpret whole soil profile trends in biogeochemical proxies. Currently, Theodore is conducting isotope analysis of authigenic clays that formed across the Eocene-Oligocene Boundary, in the Great Plains of North America. The particular motivations for this research are to (1) characterize and interpret isotopic changes with depth, (2) evaluate level of agreement with other proxy measurements from the same geologic setting, (3) compare paleoclimatic and paleohydrologic interpretations with existing research, and (4) further the understanding of isotope systematics in soils and paleosols. Future projects include multi-proxy analysis of late Cretaceous paleosols formed in China’s Songliao Basin and the Hell Creek Formation of Montana. Theodore is a GSA, AGU, and IBES member. Theodore is also ready to tell you all about his new daughter, just ask!


M. Justin Custado (IBES Profile) – DEEPS Graduate Student (2nd year)

B.S. Chemistry, University of the Philippines – Diliman, 2015 & M.S. Environmental Science, University of the Philippines – Diliman, 2021

Justin‘s research interests span broadly within the fields of aquatic geochemistry (e.g., spatiotemporal variation of chemical species through water systems) and hydrology related to climate processes (e.g., investigating the response of hydrological parameters to events such as the ENSO). Originally from a hot and humid country (the Philippines), he moved to Providence in the Fall of 2022 and is currently struggling with the cold New England weather.
  • Mónica Geraldes Vega – DEEPS Graduate Student (1st year) – co-advised by Kim Cobb

B.A. Geological Sciences, Mount Holyoke College, 2022

Mónica is broadly interested in paleoclimate, biogeochemistry, and geochronology. Her undergraduate work at Mount Holyoke College involved deciphering siliciclastic paleolake levels of a Jurassic rift lake in Western Massachusetts using physical and geochemical proxies. At Brown, she’s switched gears a little and is into learning about more geologically recent carbonate records via stalagmite samples from the Philippines. She is driven by questions related to tropical paleoclimate and general excitement about learning and sharing knowledge. She is also enjoying her transition from her native Dominican Republic to Providence life, where she is getting better at cooking every day.


Research Associates

Jesse Miller, B.A. with Honors, Geological Sciences, Brown University, 2023

Summer 2022 SPRINT|UTRA Award and Research at Brown Grant

2023 GSA NE-SE Regional Meeting Presentation: Temperature Dependent Dissolution Experiments of Basalt, Dacite and Pumice from The Little Deschutes River Valley

Senior thesis: Temperature dependent dissolution experiments of basaltic andesite, dacite and pumice from the Little Deschutes River Valley, Oregon

Manuscript Forthcoming!



Shaw Miller, B.S. Candidate Geology-Biology, Brown University, 2023.5

Summer 2022 SPRINT|UTRA Award

2023 Sarah LaMendola Undergraduate Research Award

Shaw is a rising fourth-year undergraduate at Brown studying evolutionary processes that shape the climate, surface, and biology of our home planet. He is currently working on a project with Cathy that uses stable isotopes of carbonate and clay material in Pleistocene lake sediments to reconstruct past climate. Additional research work includes GIS analysis of watersheds and preparation of clay samples for isotopic analysis. Outside the lab, he is active in Brown’s marching band and enjoys riding (or tinkering with) bicycles and rock climbing.

Anna Dubey, B.A. Candidate, Ecology, Evolution, & Organismal Biology, Brown University, 2025.

Anna is a second-year student at Brown studying Biology, as well as Comparative Literature in Ancient Greek. Her research interests lie at the intersection of evolutionary biology and climatology. She is currently working on a project with Cathy using carbonate isotope data from Searles Lake in San Bernardino County, CA, to gain an understanding of the paleoclimate. Other than research, her activities include working for climate activism movements and educating high school students in earth science and environmental justice.


Celia Kong-Johnson, B.S. Candidate Geology-Chemistry, Brown University, 2025

Fall 2023 SPRINT|UTRA Award

I am a current second-year at Brown University and plan on concentrating in geochemistry, with a possible double concentration in applied math. I am most interested in paleoclimate studies and applying these findings to future climate change research. I am currently working with Natasha, analyzing carbon and oxygen isotope records in speleothems from Colombia and the Philippines to help model past vegetation and rainfall in the area. Outside of academics here at Brown, I am on the Track and Field team. I also enjoy visiting and exploring National Parks with my family.


Daniel Graves, B.S. Candidate, Environmental Sciences, Brown University, 2024

I am a junior at Brown University studying Environmental Sciences on the Conservation track. I am interested in conservation and sustainability and modeling paleoclimate. In the lab, I am working on a senior thesis recreating past precipitation environments in the Great Basin by using water balance modeling and lake level proxy data. Outside of the lab, I play frisbee and am involved in the Brown Outdoor Leadership Training.


Jonah Bernstein-Schalet, B.S. Candidate Geology-Biology, Brown University, 2024.

2023-24 Voss Undergraduate Fellowship Award

Jonah is a 3rd-Year Undergraduate who is enthusiastic about learning about all things related to the Earth. He loves spending time outside applying concepts from the classroom to understand the many processes occurring around him. Currently, he is interested in using soil and water samples to characterize the impact of wildfires on catchment-scale chemical and physical weathering. Previous lab work includes generating sea-surface temperature records using biomarkers in ocean-floor sediment cores. Outside of science, Jonah is passionate about fitness, hiking, and philosophy.


A young white adult is pictured squatting outside in front of green trees and shrubs, with mountains a town in the distance. They are smiling and squinting, facing the sun. They’re wearing a light blue jean jacket over a dark green shirt, a multi-colored bag strap on their left side, and a small silver necklace. Whitney Vieira Ribeiro, B.S. Candidate Geology-Biology, Brown University, 2024.

Whit is a third-year undergraduate at Brown University concentrating in geobiology. They are interested in questions about periods of extinction and transition in the geologic record. Currently they’re working with Ted to reconstruct end-Cretaceous climate using carbon clumped isotopes in paleosols from the Songliao basin, China. Whit loves finding earth-science workbooks and thinking about developing accessible modes of science education. They also enjoy running, playing Sudoku, and spotting paw prints in sidewalk cement.


Marina Benson, B.S. Candidate Geology-Biology and B.A. Candidate Music, Brown, 2024

2023-24 Voss Undergraduate Research Fellow

Marina is a senior at Brown who is interested in the impact of human activities on aquatic ecosystems. In collaboration with the Marine Biological Laboratory, Marina examines trace metals and stable isotopes to identify sources of nutrient pollution in estuarine ponds on Martha’s Vineyard. Her research seeks to understand how pollutants impact the broader biological communities within the ponds. In past research she has used isotope paleothermometry to look at Indian Summer Monsoon dynamics over orbital and millennial timescales. Outside of lab work, Marina enjoys participating in campus theatre and performing with her jazz-funk band, Em’s Femmes.

Maira Rojas-Tineo, Brown, 2025

Fall 2023 SPRINT|UTRA Award

I am a junior at Brown University studying Environmental Engineering and International and Public Affairs on the Development track. I am interested in the intersection of sociopolitical shifts, and “green” innovations and expansions in Latin America. More specifically, I aim to focus on the recent emergence of sustainable energy systems and alternative lithium extraction techniques in the context of recent political developments in Chile, and Argentina. During this upcoming semester, I will be working with Kristina on climate transitions in the Salar de Atacama Basin in Northern Chile, and the analysis of temperature trends. In addition to this research, I work on political science projects studying strikes and police violence. Outside of school, I enjoy hiking, open water swimming, and urban farming!


Former Group Members

Dr. Kristina Butler (; – NSF EAR Postdoctoral Fellow, 2023

B.S. Geological Sciences, University of Alaska Anchorage 2017; Ph.D. Geological Sciences, University of Texas at Austin, 2022

Now Assistant Professor at UT Dallas!



Annabelle Gao, B.S. Geology-Chemistry, Brown University, 2023

Coauthor on Gagnon et al. (2023, GSA Bulletin) and several forthcoming manuscripts.





Christina Marsh, DEEPS Leadership Alliance REU, Summer 2022, B.A. Environmental Analysis, Pomona College, 2023


Manuscript In Review!



Mia Prausnitz-Weinbaum, B.S. Candidate Environmental Studies, Brown University, 2024






Natalie Chang, B.A. Candidate, Geology-Biology and Modern Culture & Media, Brown University, 2024

Summer 2022 SPRINT|UTRA Award






Elizabeth (Lizzy) Gaviria (LinkedIn) – DEEPS Leadership Alliance REU, Summer 2021/Independent Study 2021-22 Academic Year – B.S. Environmental Science, Rice University, 2022

2022 AMS Annual Meeting Presentation: Modeling seasonal and interannual climate variability in modern precipitation pathways across western North America using air parcel trajectories

Coauthor on Gagnon et al. (2023, GSA Bulletin)

Lab Visitors

Dr. Jaivime Evaristo – Assistant Professor, Utretch University – Spring 2023 (Website)

Bryce Belanger – Ph.D. Candidate, Vanderbilt University – Summer 2023

Jiquan Chen – Ph.D. Candidate, China University of Geosciences (Beijing) – Fall 2023 to Winter 2024


Lab Affiliates

Dr. Christopher W. Kinsley – Postdoc at Berkeley Geochronology Center, 2022-Present

Dr. Anna Waldeck – Agouron Postdoctoral Research Fellow, DEEPS, 2023-Present

Dr. Dean Kahn – Research Associate, DEEPS, 2022-Present

Dr. Soumen Mallick – ICPMS Analysis Specialist/Research Scientist, DEEPS, 2022-Present



Knuckles and Gigi