Research Symposium

BIO

Jonah Karpf is a senior chemistry major pursuing a career in geochemistry. At FSU he has worked with Dr. Jeremy Owens to reconstruct the oxidation of Earth's ancient oceans using the chemical makeup of ocean sediments. In the Fall of 2026, he will start a M.S. in Geology at Iowa State University, focused on analyzing the rate of continental emergence in Earth's distant past. He is the president of the fencing club at FSU, and enjoys drumming and duck photography.

Redox geochemistry of an early Ordovician deep water shale: potential implications for Earth's largest radiation event

Abstract

The Great Ordovician Biodiversification Event (GOBE) was one of the most dramatic radiations of life in Earth’s history, and constraining the factors responsible is key to understanding the nature and development of life on the planet. To this end, stratigraphic sections of rock formed from ocean sediments are analyzed geochemically to form interpretations about the paleoclimate and the state of Earth’s oceans directly before and during the GOBE. In this study, a rare section that preserves deep water shale from the early GOBE is examined. This shale is from the Cow Head Group in western Newfoundland and was originally deposited on the coast of Laurentia.

Here, analysis of the depositional redox conditions of the section using iron content and speciation, reduced sulfur, and bulk rock elemental abundances are presented. This geochemistry provides insights into the local bottom water oxygen availability of one of the last regions to become oxidized prior to the GOBE. Increased molecular oxygen availability has been implicated as a driving cause of the GOBE, thus these findings provide key information for the radiation of Ordovician life. Measurements of the highly reactive iron components of these shales are compared with total iron concentrations and pyrite-associated iron to track how oxidized the depositional conditions were. These measurements are combined with trace element concentrations that are influenced by the redox conditions they are deposited under. Through these varied methods, a picture of the oxygen availability of the Earth’s oceans for the initial phase of the GOBE can be formed.

Keywords: Geochemistry, Geology, Chemistry, Seawater, Evolution