GSA Connects 2021 in Portland, Oregon

Paper No. 75-1
Presentation Time: 8:10 AM


MARROQUÍN, Selva, Caltech, 1200 E California Blvd, MC 100-23, Pasadena, CA 91125, CARUTHERS, Andrew H., Department of Geological and Environmental Sciences, Western Michigan University, 1903 W. Michigan Ave, Kalamazoo, MI 49008-5241, ABERHAN, Martin, Museum für Naturkunde, Invalidenstr. 43, Berlin, 10115, Germany, GOLDING, Martyn, Natural Resources CanadaGeological Survey of Canada, 1500-605 Robson Street, Vancouver, BC V6B5J3, CANADA, GRÖCKE, Darren R., Department of Earth Sciences, Durham University, South Road, Durham, DH13LE, United Kingdom, MCCABE, Kayla, Department of Geosciences, Virginia Polytechnic Institute and State University, 4044 Derring Hall, Blacksburg, VA 24061, OWENS, Jeremy, Florida State UniversityEarth, Ocean and Atmopsheric Science, EOAS Building 1011 Academic Way, Tallahassee, FL 32306-4100, THEM II, Theodore R., Department of Geology and Environmental Geosciences, College of Charleston, Charleston, SC 29424, TRABUCHO ALEXANDRE, João, Institute of Earth Sciences, Utrecht University, Heidelberglaan 2, Utrecht, 3584 CS, Netherlands, VEENMA, Yorick, Institute of Earth Sciences, Utrecht University, Budapestlaan 4, Utrecht, 3584 CD, Netherlands and GILL, Benjamin, Department of Geosciences, Virginia Tech, 926 West Campus Drive, Blacksburg, VA 24061

The Triassic-Jurassic boundary interval was a time of intense disturbances to marine communities and notably contains one of the largest extinctions of the Phanerozoic, the end-Triassic mass extinction (ETE, ~201 Ma). This interval is also characterized by major carbon cycle perturbations and potentially widespread oxygen deficiency within the oceans. While the cause(s) of extinction and environmental feedbacks are still debated, and under constrained, they are hypothesized to have been triggered by massive volcanism associated with the Central Atlantic Magmatic Province flood basalts. Whereas carbon isotope (δ13C) records immediately preceding the Triassic-Jurassic boundary (i.e. ETE interval) have been generated globally, there remains a lack of continuous, long-term records that capture the global carbon cycle prior to and well after the ETE. We seek to expand our understanding of the carbon cycle and environmental changes across this critical time interval by reconstructing a long-term δ13C record from a sedimentary section preserved in the Wrangell Mountains of Alaska that spans the Norian (Late Triassic) to Sinemurian (Early Jurassic) stages (~227–190.8 Ma).

The section studied at Grotto Creek represents distal facies of a mixed carbonate-silica ramp deposited on an isolated plateau at tropical latitudes in the open Panthalassan Ocean. This succession provides a unique window into open marine conditions and also holds the potential for excellent temporal control as it contains abundant ash layers throughout, as well as key ammonoid, bivalve, and conodont fossil occurrences providing robust biostratigraphic control. In our organic δ13C data, we observe distinctive excursions at the Norian/Rhaetian boundary. δ13C broadly increases higher in the Hettangian and decreases across the boundary into the Sinemurian. These findings are generally consistent with records generated elsewhere and provide key constraints to our understanding of local versus global signals preserved in the δ13C record. Thus, improving our ability to tie mechanistic triggers more precisely to the biotic crises surrounding the Triassic-Jurassic boundary interval.