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 Researchers
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.
Michael Fuhr is a Yale Center for Natural Carbon Capture (YCNCC) Postdoctoral Research Fellow. Michael investigates the potential and the limitations of enhanced benthic weathering (EBW) of calcite as a process for ocean alkalinity enhancement (OAE). His research focus lies at the interplay of biotic and abiotic sedimentary processes that drive natural and enhanced carbonate weathering and possible pathways to extrapolate a sedimentary system’s capacities to produce additional alkalinity via calcite-based EBW as a climate change mitigation method.
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.
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 and Postgraduate Researchers
Maxwell Cota is a senior undergraduate double-majoring in Earth and Planetary Sciences and Global Affairs. For his senior thesis, he is working with Kate and Lidya to research biogeochemistry and bioturbation in Permian glass ramp ecosystems. He also previously worked with Brian and Lidya on studying seafloor animal recovery following the End-Permian Mass Extinction.
Tarhan Lab Alumni
Postdoctoral Researchers
Rachel Surprenant (Yale Seessel Postdoctoral Fellow, 2025; currently Assistant Professor at San Diego City College): Rachel conducted taphonomic experiments investigating the impact of decay on the morphologies of green and red macroalgae.
Olmo Miguez-Salas (visiting Yale Postdoctoral Associate, 2024; currently Beatriu de Pinos Fellow, University of Barcelona): 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
Brian Beaty (Yale Ph.D. 2019–2025; currently Postdoctoral Researcher at Stanford University): For his minor discourse in the Tarhan Lab, Brian investigated bioturbation-biogeochemical feedbacks across the Permian-Triassic mass extinction interval of Svalbard.
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.
Postgraduate Researchers
Noah Slaney (Yale Postgraduate Researcher 2025; currently M.Sc. student at Memorial University): As a YIBS Summer Undergraduate Research in Environmental Science Fellow, Noah worked with Kate, Maya and Lidya to investigate Zoophycos in Devonian successions of the Appalachian Basin, document burrow silicification and characterize bioturbation in modern muds of the deep Atlantic seafloor.
Undergraduate Students
Andrea Chow (Yale B.S. 2025; Tarhan Lab 2024–2025): Andrea worked with Kate and Lidya to analyze relationships between Devonian and Carboniferous bioturbation and organic carbon and reduced sulfur preservation..
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. 2025; Tarhan Lab 2022–2023): Victoria assisted Lidya and Silvina with processing SEM photomicrographs of fossilization experiments to reconstruct pathways of authigenic mineralization.