221 Phanerozoic Earth System Shifts in the Marine Sedimentary Record (Posters)

This session explores Earth System shifts documented as perturbations to the Phanerozoic geochemical, lithological, and biogeochemical marine records, leading to climate shifts, anoxia, ocean acidification, and extinction events.

Tuesday, 21 October 2025
8:00 AM - 5:30 PM
HBGCC, Hall 1

Insights on Redox Conditions Through the Great Ordovician Biodiversification Event From Deep Water Facies of Western Laurentia

Paper number: 221-1
Program: Technical Sessions
Time: 8:00 AM – 8:00 AM

Authors

Abstract

The Great Ordovician Biodiversification Event (GOBE) was a pivotal period of biodiversification in marine life. Familial diversity had increased three-fold accompanied by an expansion and restructuring of marine ecosystems. The cause of this radiative event has been attributed to a multitude of biotic and abiotic factors from the proliferation of phytoplankton, enhanced nutrient supply, increased marine oxygenation, and a cooling global climate. Geochemical data from a variety of scales and depositional environments are needed to better constrain the timing and magnitude of marine redox dynamics during this period. It is important to constrain the role of marine redox dynamics during radiation periods as it provides insights into post extinction intervals and expectations of life beyond Earth.

In this study we have analyzed carbon isotopes, iron speciation, and trace metals from organic-rich mudstones of the Phi Kappa Formation at Trail Creek summit in central Idaho. This section has been constrained to the Early (Floian) through Late Ordovician (Katian) using graptolite and conodont biostratigraphy. Imperatively, the carbon isotopes, in concert with biostratigraphy, will provide chemo- and biostratigraphic correlation with other globally recognized localities. The carbon contents and isotopes provide a foundation to interpret local geochemical redox proxies. To understand local redox conditions under which these organic-rich mudstones were deposited, we utilize iron speciation to quantify the proportion of oxide vs reduced iron minerals to identify anoxic and euxinic conditions. A suite of trace metal concentrations (Mn, V, and Mo) will be used to assess the local redox conditions for specifically early anoxic to sulfidic conditions. Notably, if the local redox conditions are relatively stable and reducing, then the trace metal enrichments of V and Mo can be utilized to constrain global redox conditions. This geochemical dataset will provide a new perspective on deepwater oxygenation on the western margin of Laurentia and its role in local and global biodiversification during the Ordovician.

Geological Society of America Abstracts with Programs. Vol. 57, No. 6

doi: 10.1130/abs/2025AM-414635

© Copyright 2025 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.