Luncheon Lecture: November 24th-Marieke Dechesne, USGS

About this event

Coring the greenhouse: Sedimentation and vegetation change during the Paleocene – Eocene Thermal Maximum in the Hanna Basin, Wyoming

Marieke Dechesne, USGS

Abstract:

The Paleocene – Eocene Thermal Maximum (PETM, 56 million years ago) is a rapid global warming event caused by the release by carbon into the atmosphere and oceans. This large perturbation of the carbon cycle caused ocean acidification, 5-9 °C of global warming, changes to the hydrologic cycle, and biotic turnover. We identified the location of the PETM in the Hanna Basin of south-central Wyoming, USA, using outcrop observations, leaf macrofossils, palynological analysis and a negative δ¹³C isotope excursion (CIE). The PETM occurs in the upper part of the Hanna Formation, which is composed of paludal to lacustrine carbonaceous shales, coals, and fluvial sandstones.

Sagebrush and colluvium obscure intervals critical to obtain a full and continuous record of the latest Paleocene, PETM, and post-PETM early Eocene. Therefore, two cores were drilled ~800 m behind a measured PETM outcrop section. Together, these cores extend to a depth of 1236 ft (377 m). The cores are correlated with the previously established outcrop-based stratigraphic framework for this area, enabling better constrained analysis of facies changes during the PETM. The excellent recovery of especially the organic rich sections in the cores will help refine spatial resolution of the δ¹³C isotope excursion, develop a more detailed palynological record, look at fire markers, track elemental changes, and deepen our understanding of paleoenvironmental dynamics in the Hanna Basin during the rapid global climatic change of the PETM. We welcome collaboration on geochemical, palynological, or other analyses from these cores.

Bio:

Marieke Dechesne is a research geologist in the Geosciences and Environmental Change Science Center at the U.S. Geological Survey in Denver. Her interest is in reconstructing basin history and building stratigraphic frameworks for the Laramide basins surrounding the Front Range in Colorado and Wyoming to learn more about their uplift history. She has a similar project in the Paleozoic Arkoma basin in Arkansas. Marieke has been mapping in the Hanna Basin since 2014 and is currently mapping the Medicine Bow 100k sheet, which includes the Hanna Basin, where she and her team, recently drilled a core. She has a MSc degree in geology from Utrecht University, Netherlands.

Registration is open, click the dunes to register!

Event Registration

This is an in-person and online event!

The cost is $30.00 for current members and $40.00 for non-members. Zoom registration is $10.00 ($5.00 for students). Unemployed individuals may sign up for lunch for just $20.00. Students may sign up for lunch for $20.00. Persons who do not wish to have lunch are welcome for a $20.00 fee. Walk-ins may purchase a lunch for the standard fees ($30.00 or $40.00) although quantities are limited. Walk-ins without a lunch are charged a $15.00 fee.

Please submit reservations by 10:00 a.m. the Friday before the talk.

Reservations may be secured online or by e-mail at information@rmssepm.org