News – Lidya Tarhan

November 7, 2023—Fall ’23 semester

It has been a busy semester for the lab!

First and foremost, this semester we welcomed two new members to the lab–Maya LaGrange Rao and Dana Polomski! Maya is a Yale Institute for Biospheric Studies (YIBS) Donnelley Postdoctoral Research Fellow who joins us after completing her PhD at University of Alberta. Maya will be working on comparing Pleistocene and modern bioturbation in Willapa Bay, WA, to better understand the response of coastal bioturbation to climate change. Dana is a senior undergraduate EPS major at Yale who is working on Mesozoic bioturbation with James and mid-Paleozoic bioturbation and its impact on sediment geochemistry with Kate. Welcome Maya and Dana!

Maya has already made significant headway on her project—in late September, Lidya and Maya visited the west coast for five days of fieldwork at Willapa Bay in southern Washington. Joined by Brette Harris and Murray Gingras from the University of Alberta, they conducted preliminary fieldwork examining Pleistocene intertidal flat deposits, which will be followed by a more extensive field campaign in spring 2024.

Brette, Murray, and Lidya moments Racoon and human footprints in the

away from wading through the rising tide. modern mudflat at Willapa Bay, WA.

Also in September, lab members James Pierce and Dana Polomski spent ten days in Wyoming working on characterizing Mesozoic bioturbation in deposits recording the Jurassic Sundance Seaway! This project is part of James’s minor discourse reconstructing the extent and styles of bioturbation during the Mesozoic Marine Revolution and follows on a scouting trip James and Lidya took in April of this year.

James and Dana logging sections in Wyoming.

In October, Lidya, Kate, Ashley, Sydney, and Jiuyuan traveled to Pittsburgh, PA for the 2023 Geological Society of America (GSA) conference. Lidya presented “NO EVIDENCE FOR MARINE DISSOLVED ORGANIC CARBON DRIVING CHANGES IN EDIACARAN ECOLOGY AND DIVERSITY“, Kate presented “PHANEROZOIC TRENDS IN THE DEPTH OF MARINE BIOTURBATION“, Ashley presented “MORPHOLOGY AND FOSSILIZATION OF GAOJIASHANIA FROM THE UPPER EDIACARAN DUNFEE MEMBER, DEEP SPRINGS FORMATION, NEVADA, USA“, Sydney presented “EXPLORING PATHWAYS OF SOFT-TISSUE PRESERVATION USING GEOCHEMICAL MODELING“, and Jiuyuan presented “EARLY DIAGENETIC EVALUATION OF STABLE STRONTIUM ISOTOPES IN SHALLOW CARBONATE SEDIMENTS“.

Ashley and Sydney arrive in Pittsburgh for GSA 2023!

After GSA, Kate and Sydney spent 10 days in the field in West Virginia and southern Pennsylvania characterizing bioturbation styles and intensitis in Devonian- and Carboniferous-aged units. This research supports Kate’s dissertation investigating changes in sedimentary mixed layer depth in the mid-Paleozoic and was supported by a Paleontological Society Student Grant. Results will be combined with findings from Kate’s previous fieldwork in the northern Appalachian Basin (New York and Pennsylvania) in a forthcoming publication.

Kate logging a roadcut section in WV. A roadcut in WV with beautiful bedding planes and trace fossils!

August 2, 2023—Tarhan Lab summer activities

Members of the Tarhan Geobiology lab have had a busy summer filled with field work, trips, and conferences!

Postdoc Sophie Westacott wrapped up her year with us at Yale and moved to Bristol, UK to start a postdoc continuing her work on the silica cycle in the modern and in deep time. Best wishes to Sophie in her new position!

In May, Lidya, Ashley, Kate, and Sydney spent two weeks in the Great Basin (southern Nevada and western Utah) studying bioturbation and trace fossils preserved in shallow-marine carbonates deposited during the late Cambrian to mid-Ordovician. They were joined by colleagues from Virginia Tech (Ben Gill) and Smith College (Sara Pruss) and their students as part of a NASA exobiology grant to study the geochemical and paleobiological conditions between two of life’s greatest radiations: the Cambrian Explosion and Great Ordovician Biodiversification Event.

Heavily bioturbated Ordovician carbonates of Member Ope of the Pogonip Group in the Arrow Canyon Range, NV.

Lidya and Smith College undergraduate Bethany Stephens measure a section of the Kanosh Formation at Crystal Peak.

In June, Kate and Sydney continued working in the Great Basin for Kate’s PhD project searching for signs of bioturbation and the development of the marine sediment mixed-layer. They worked on Devonian and Carboniferous strata at several localities across southern and central Nevada and were partly joined by colleague Diana Boyer (Winthrop University) and her students.

Kate and Sydney getting ready to measure a section of the Joanna Limestone at Bactrian Mountain.

Kate checking out some Devonian trace fossils of the Guilmette Formation at Gap Mountain.

In June, Silvi and Sam went on the department field trip to Greece and visited geological sites all over the country! They both continued on to the Goldschmidt geochemistry conference in Lyon, France, where Silvi presented her poster “The Role of Substrate and Seawater Geochemistry in Shaping the Fossilization of Earth’s Earliest Animal Communities.”

Silvi standing at a contact between volcanic units and conglomerates in Santorini during the EPS field trip.

In July, Lidya and Sydney joined colleagues from Stanford (Erik Sperling and Emily Ellefson) and the Geological Survey of Canada (Keith Dewing) for an Arctic expedition to Bathurst Island, Nunavut to study Silurian-Devonian marine shales that capture geochemical conditions during the rise of early land plants. They collected hundreds of samples for a variety of geochemical analyses, saw a polar bear, and found plant fossils!

Keith, Emily, and Lidya hard at work measuring a section of the shale-rich Ordovician-Silurian Cape Phillips Formation on central Bathurst Island.

Devon Manik, a local hunter and wildlife monitor, who joined the expedition, introduced the group to his team of sled dogs and their puppies. Pictured: Lidya cuddling an Inuit sled dog puppy.

Last but not least, Kate’s undergraduate research was recently published in Palaeogeography, Palaeoclimatology, Palaeoecology! The title of her paper is “Appalachian Basin mercury enrichments during the Late Devonian Kellwasser Events and comparison to global records.” Link to the paper is here. Congratulations, Kate!