221-2 Insights on Redox Conditions Through the Great Ordovician Biodiversification Event From Deep Water Facies of Western Laurentia

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

Poster Booth No.: 138

Presenting Author:

Charlie Smith

Authors:

Smith, Charlie A.¹, Adiatma, Yoseph Datu², Owens, Jeremy D.³, Goldman, Daniel⁴, Leslie, Stephen A.⁵, Young, Seth A.⁶

(1) Florida State University, Tallahassee, Florida, USA, (2) Florida State University, Tallahassee, FL, USA, (3) Florida State University, Tallahassee, FL, USA, (4) University of Dayton, Dayton, OH, USA, (5) James Madison University, Harrisonburg, VA, USA, (6) Florida State University, Tallahassee, FL, USA,

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, 2025

doi: 10.1130/abs/2025AM-10840

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