Principal Investigator
Lidya Tarhan attended Amherst College where she majored in Geology and English and worked on body and trace fossils and the sedimentology of Cambrian shoreline deposits, cementing her love of sandstones, exceptional fossilization and exploring the co-evolution of ecosystems and environments. She pursued her M.S. and Ph.D. at the University of California, Riverside—studying the taphonomy and paleoenvironment of the Ediacara Biota of South Australia and the evolutionary history of bioturbation, respectively. She then moved to Yale University for her postdoctoral studies, including an NSF-EAR Postdoctoral Fellowship focused on the fossilization of Earth’s earliest animal communities, before joining the faculty of the Department of Earth and Planetary Sciences as an Assistant Professor in 2019. Lidya additionally became an Assistant Curator in the Division of Invertebrate Paleontology of the Yale Peabody Museum in 2021.
Postdoctoral Scholars
Maya LaGrange Rao is a Yale Institute for Biospheric Studies (YIBS) Donnelley Postdoctoral Research Fellow. Maya’s research focus lies at the intersection of geobiology and geochemistry; in particular, she is interested in understanding past marine conditions through trace fossils and chemical proxies recorded in sedimentary rocks. By comparing bioturbation in ancient coastal rock units to present-day coastal sediments, Maya’s work with the Tarhan Lab will investigate the response of shoreline burrowing animals to environmental change.
Rachel Surprenant is a Yale Seessel Postdoctoral Fellow. Rachel’s research focuses on Ediacaran paleobiology and taphonomy, with a particular focus on tubular organisms. As the most commonly occurring body plan in the terminal Ediacaran, tubular organisms hold broad significance for our understanding of the evolution of animal life on Earth. However, the simple, hollow and elongate bodies that characterize tubes lead to substantial biostratinomic overprint on their fossil record and their common misidentification as trace fossils, macroalgae, or sedimentary structures. Rachel’s research in the Tarhan Lab will leverage biostratinomic observations to reconstruct paleobiological traits and paleoecological strategies of tubular organisms in order to establish a framework for their accurate identification as complex body fossils and to ascertain their roles in Ediacaran ecosystems.
Graduate Students
Kate Pippenger is a Ph.D. student and NSF Graduate Research Fellow. Her research centers around the many different ways that organisms interact with their environments, especially during intervals of significant environmental and evolutionary change. In particular, she is interested in tracking the effects of ecosystem engineers throughout geologic time, and is currently focused on reconstructing mid- to late-Paleozoic increases in bioturbation intensity to explore the effects of an increase in mixed layer depth. As a Ph.D. student in the Tarhan Lab, she utilizes a combination of paleontological, sedimentological, and geochemical methods to answer these questions, and is also interested in projecting conclusions drawn from her deep-time research into the modern age to inform conservation and climate mitigation strategies.
Sydney Riemer is a Ph.D. student. She comes to Yale after completing a M.Sc. from Ben-Gurion University, where she researched the impact of bioturbation on the sulfur isotope record. She is broadly interested in understanding the mechanisms behind the coevolution of Earth’s surface environment and complex ecosystems during biological radiations/extinctions and environmental perturbations using a combination of tools from paleontology, isotope geochemistry, and sedimentology. She is also interested in exploring large datasets and integrating geochemical and paleontological data into various types of models. For her Ph.D. Sydney is investigating how early land plant communities shaped the Earth system, including potential shifts in marine nutrient cycling associated with changes in continental weathering intensity.
Ashley Rivas is a Ph.D. student. Her interests include environmental changes and how they affect fossil abundance and diversity through the Precambrian and early Paleozoic. She is primarily interested in early radiation events and what fossil assemblages during these intervals can tell us about their ancient environments and ecologies. For her Ph.D. she is investigating relationships between bioturbation and environmental change in the interval leading up to the Great Ordovician Biodiversification Event.
Lauren Gregory is a Ph.D. student and NSF Graduate Research Fellow. She earned her M.S. in Geology from California State University Fullerton, where she researched Triassic reef recovery following the end-Permian mass extinction. She has a broad interest in the evolutionary and environmental factors that contribute to long-term ecological change. In the Tarhan Lab she will investigate the interactions between evolutionary innovations and geochemical change, focusing on the radiation of biomineralization and Paleozoic transitions in the marine carbonate factory and carbonate saturation states. She employs paleontological, geochemical, and sedimentological methods in her research.
Brian Beaty is a Ph.D. student, working in the Tarhan Lab for his minor discourse project on investigating potential feedbacks between bioturbation and ocean anoxia in deep time via bioturbation’s impacts on the marine phosphorus cycle. He is using the Permian-Triassic mass extinction in Svalbard as a case study. Broadly, he is interested in global Earth-system responses to major climate perturbations in deep time, including weathering on land as well as acidification and deoxygenation in the oceans, and how the geochemical composition of sedimentary rocks captures these changes in the geologic record.
Sam Shipman is a Ph.D. student doing a minor discourse project in the Tarhan Lab. He is an isotope geochemist and geochronologist currently focused on constructing age and paleoweathering frameworks for Cryogenian and Ediacaran sedimentary successions. His research in the Tarhan Lab employs stable strontium isotope geochemistry to investigate carbonate saturation state during the Cambrian.
James Pierce is a Ph.D. student completing his minor discourse in the Tarhan Lab. His work focuses on Earth History, including paleogeography and stratigraphy. James is studying bioturbation in the Jurassic Sundance Formation in central Wyoming. Bioturbation, the mixing of sediment at or below the sediment-water interface, is consequential to marine biogeochemistry including the oxygen and phosphorus cycles. The mixed layer constitutes the uppermost and most intensely bioturbated layer of sediment. However, it has not been well characterized in the Mesozoic, despite its importance. Understanding the effect that bioturbation had during the Jurassic will help us to understand this crucial interval that witnessed a drastic increase in biological innovation when the modern structure of benthic ecosystems was established.
Nicolas Theunissen is a Ph.D. student working in the Tarhan Lab on his minor discourse, for which he is calibrating several widely used textural and geochemical proxies for the depth of the sedimentary mixed layer. He also previously worked as a postgraduate associate in the Tarhan Lab, studying the impact of marine heatwaves and low-oxygen events on bioturbation intensities in Long Island Sound. He uses environmental control chambers and an aquarium system to incubate naturally occurring bioturbator communities.
Undergraduate Students
Andrea Chow is a senior undergraduate Earth and Planetary Sciences and Ethnicity, Race and Migration double major. She is working with Kate and Lidya to explore relationships between ancient bioturbation and seafloor biogeochemistry. She is analyzing Devonian and Carboniferous samples from the Appalachian and Great Basins to investigate how bioturbation influences organic matter and sulfur preservation in marine sediments, providing insights into past environmental conditions.
Tarhan Lab Alumni
Postdoctoral Scholars
Olmo Miguez-Salas (visiting Yale Postdoctoral Associate, 2024; currently Postdoctoral Fellow at the Universidad de Granada and Senckenberg Research Institute): Olmo conducted incubation chamber experiments to explore the impact of warming and deoxygenation on burrow morphology and mixed layer development.
Jiuyuan Wang (Yale Postdoctoral Associate and Agouron Geobiology Postdoctoral Fellow, 2021–2023; currently Assistant Professor at Peking University): Jiuyuan used the stable strontium isotope signature of carbonates to reconstruct the evolution of the carbonate factory through Earth’s history.
Sophie Westacott (Yale Seessel Postdoctoral Fellow, 2022–2023; currently postdoctoral researcher at University of Bristol): Sophie investigated the silicon isotopic signature of modern radiolarians as well as the biogeochemical impact of Cambrian deep burrowing.
Thomas Boag (YIBS Donnelley Postdoctoral Fellow, 2020–2022; currently Director of Decanal Affairs, Division of Natural Sciences, Columbia University): Tom used a combination of petrographic and geochemical methods to investigate the role of clays in fostering Ediacara-style fossilization.
Ph.D. Students
Silvina Slagter (Yale Ph.D. 2021–2024; currently Assistant Professor at Universidad de O’Higgins): Silvina used a jointly experimental and fossil-based approach to reconstruct Ediacaran and Paleozoic silica cycling, including interrogating the role of seawater dissolved silica levels, organo-silica interactions and substrate mineralogy in shaping the fossilization of the Ediacara Biota.
Maoli Vizcaíno (Yale Ph.D. 2021–present): For her minor discourse in the Tarhan Lab, Maoli conducted incubation experiments to explore the impact of warming on the burrowing activities of starlet anemones.
Tom Reershemius (Yale Ph.D. 2019–2024; currently Lecturer at Newcastle University): For his minor discourse in the Tarhan Lab, Tom investigated the facies relationships, petrography and taphonomy of Cambrian tubular fossils.
Undergraduate Students
Dana Polomski (Yale B.S. 2024; Tarhan Lab 2023–2024; currently Ph.D. Student at MIT): Dana worked with Lidya, Kate and James to characterize Devonian and Jurassic bioturbation and explore relationships between bioturbation and organic carbon preservation.
Victoria Smithson (Yale B.S. in progress; Tarhan Lab 2022–2023): Victoria assisted Lidya and Silvina with processing SEM photomicrographs of fossilization experiments to reconstruct pathways of authigenic mineralization.