Geological Society of America

T169 Chemostratigraphy: Physical and Temporal Applications

Tuesday, 24 September 2019
8:00 AM - 12:00 PM
Room 224B, North Building

HIGH-RESOLUTION PAIRED ORGANIC AND CARBONATE CARBON ISOTOPE CHEMOSTRATIGRAPHY OF THE IREVIKEN EXCURSION (SILURIAN) FROM THE ALTAJME CORE, GOTLAND, SWEDEN

Paper number: T169-4
Program: Technical Sessions
Time: 8:50 AM – 9:05 AM

Authors

Emma R. Hartke Presenting Author
University of Iowa, Iowa City, IA
Bradley Cramer
University of Iowa Dept of Earth & Environmental Sciences, Iowa City, IA
Mikael Calner
Lund University, Lund
Stephan C. Oborny
University of Iowa, Iowa City, IA
Alyssa M. Bancroft
Indiana University, Bloomington, IN

Abstract

The Silurian Period (443-416 Ma) was defined by extensive changes to the biogeochemistry of the Earth and marked by a series of extinction events and global carbon cycle perturbations. The Ireviken Event (Llandovery-Wenlock boundary, ~430 Ma) was one of these Silurian biogeochemical events and is marked by the Ireviken positive carbon isotope excursion. This global carbon cycle perturbation produced a positive carbon isotope excursion in both the organic and carbonate carbon records and this study is the first high-resolution investigation of the paired carbon isotope record through this interval.

Upon examining the synchronicity between the organic and carbonate carbon records from this study, the data demonstrate a +2‰ increase in ∆¹³C, the difference between carbonate and organic carbon values, as well as a slight variation in the timing of the onset of events in each isotopic record. If taken as a proxy for atmospheric pCO₂ concentrations, the data suggest an increase in CO₂, and thus global temperatures. However, this is in opposition to previously published data using the oxygen isotope temperature proxy, which shows a roughly 4 degree Celsius cooling during this interval. If the oxygen isotope temperature proxy is considered to be valid, an alternative explanation for the ∆¹³C record is required. One possibility is that changes to the fractionation coefficient of marine phytoplankton, ε_p, driven by changes in global nutrient availability, could produce the changes seen in the δ¹³C_org record, even in the presence of global cooling.

Geological Society of America Abstracts with Programs. Vol. 51, No. 5

doi: 10.1130/abs/2019AM-337521

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