Geological Society of America

T68 The Ordovician Earth: Integrated Perspectives on the Fossil and Rock Records

Sunday, 22 September 2019
1:30 PM - 5:30 PM
Room 228AB, North Building

DID EARLY LAND PLANTS PRODUCE A STEPWISE-CHANGE IN ATMOSPHERIC OXYGEN DURING THE LATE ORDOVICIAN (SANDBIAN ~ 458 MA)?

Paper number: T68-5
Program: Technical Sessions
Time: 2:30 PM – 2:45 PM

Authors

Yoseph Adiatma Presenting Author
The Ohio State UniversitySchool of Earth Sciences, Columbus, OH
Matthew Saltzman
The Ohio State University, Columbus, OH
Seth Young
Florida State University, Tallahassee, FL
Elizabeth M. Griffith
The Ohio State University, Columbus, OH
Nevin P. Kozik
Florida State University, National High Magnetic Field Laboratory, Tallahassee, FL
Cole T. Edwards
Appalachian State University, Boone, NC
Stephen Leslie
James Madison University, Harrisonburg, VA
Alyssa M. Bancroft
Indiana University, Bloomington, IN

Abstract

A stepwise-change in atmospheric oxygen (O₂) levels during the Ordovician has been attributed to the emergence of land plants. This phenomenon is tied to a major baseline shift in the stable carbon isotope (δ¹³C_carb) curve, and an inferred increase in nutrient delivery, and enhanced primary productivity in nearshore settings, which led to enhanced organic carbon burial. The timing and magnitude of this baseline shift, however, is still elusive in part due to the lack of high-resolution δ¹³C data that span this period.

This study presents new high-resolution δ¹³C data from Middle to Upper Ordovician sections at Germany Valley (West Virginia) and Union Furnace (Pennsylvania) in the Central Appalachian Basin. The δ¹³C curves of the data from both sections are characterized by relative stability and low carbon isotope values (mean δ¹³C = -0.61 ‰) in the lower Sandbian, followed by a ~ 1.2 ‰ shift toward more positive values (mean δ¹³C = +0.62 ‰) in the upper Sandbian. We propose that the positive shift represents a fundamental state change in the global carbon cycle that is coincident with a major diversification of early land plants (i.e., bryophytes). This shift in δ¹³C baseline supports a growing number of studies that interpret enhanced organic carbon burial rates served as a mechanism for the stepwise oxygenation of the atmosphere during the Late Ordovician.

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

doi: 10.1130/abs/2019AM-338453

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