Lidya Tarhan

Education:

Ph.D. (2013), Geological Sciences, University of California-Riverside

M.S. (2010), Geological Sciences, University of California-Riverside

B.A. (2008), Geology and English, Amherst College

Research:

My research interests center upon using the sedimentary record to develop a multidisciplinary understanding of ancient life during key intervals in Earth’s history. I investigate the interplay between animals and environments and the role of animals as ecosystem engineers—from the micron scale to landscape- and ocean-wide scales—in both ancient and modern settings. I am also interested in processes of fossilization and the role these play in modifying the stratigraphic records of both ecosystems and environments. My group’s research combines a traditional sedimentological and paleontological approach with a geochemical and experimental toolkit and is grounded in field work as well as specimen-, laboratory- and modeling-based analyses.

Below are a couple examples of ongoing areas of research in my lab group (please see the Tarhan Geobiology Lab website for more detailed information).

Ediacaran Preservation, Paleoenvironments and Paleoecology

The Ediacara Biota, Earth’s earliest macroscopic, multicellular communities—which appeared in the fossil record just prior to the Cambrian Explosion—hold the key to reconstructing the evolution and radiation of complex life on this planet. Understanding the processes of fossilization that have shaped these deposits, as well as their geologic histories , is critical to unravel the habitats, affinities and ecologies of early complex life and distinguishing genuine evolutionary signals from preservational artefacts. My group’s recent work has focused on the mechanisms responsible for ‘Ediacara-style’ preservation (the paradoxical exceptional fossilization of soft-bodied organisms as three-dimensional casts and molds in sandstones). We use petrographic and geochemical tools (e.g., LA-ICP-MS, SEM-EDS, CL microscopy and SIMS analyses), as well as paleontological data to better understand the breadth of Ediacara-style fossil deposits and reconstruct the processes and conditions responsible for this record. Our recent work has highlighted the importance of ancient seawater chemistry and seafloor conditions in shaping this record—particularly the role of oceans rich in dissolved silica, prior to the emergence of silica-biomineralizing animals and plankton, in fostering the early diagenetic precipitation of amorphous silica cements and other silicate minerals. We also use a combination of sedimentological and geochemical tools to investigate the environmental setting and habitat of the Ediacara Biota—a topic of ongoing controversy that is crucial to deciphering the radiation of animal life.

Early Paleozoic Substrate Evolution and Mixed Layer Development

We additionally use sedimentary and paleontological records to investigate the evolutionary history of how animals and other “ecosystem engineers” have transformed their surroundings. In particular, a number of members of the Tarhan Geobiology Lab are investigating how bioturbators—burrowing and sediment-mixing animals—have, at various times in Earth’s past as well as in today’s oceans, shaped the physical properties of the seafloor, the biogeochemistry of both seafloor sediments and overlying ocean waters, and the ecology of seafloor communities. Our work has demonstrated that the depth and intensity with which animals churn the seafloor has dramatically changed seafloor habitability, seawater oxygen and sulfate levels and nutrient cycling. Additionally, our sedimentological, paleontological and geochemical modeling data are placing new constraints on the timing and pace of changes in key engineering behaviors like bioturbation—including new awareness of the extent to which increases in the efficiency and environmental range of seafloor bioturbation lagged major evolutionary milestones in early animal history like the Cambrian Explosion and the Great Ordovician Biodiversification Event, and the manner in which mass extinctions and climate perturbations may, by impacting burrowing animals, have exacerbated biotic and environmental crises and delayed ecosystem recovery.

We also investigate the history of other key organism-environment interactions, such as the evolution of the marine carbonate factory and early land plants.  Please see the Tarhan Geobiology Lab website for more information on our recent research.