T12 Advances in Using Sedimentary Data to Constrain the Timing and Rates of Geologic Events and Processes I

Sunday, 22 September 2019
8:00 AM - 12:00 PM
Room 222BC, North Building

CHEMOSTRATIGRAPHY AND SEDIMENTOLOGY OF THE DINOSAUR CANYON MEMBER, MOENAVE FORMATION: IMPLICATIONS FOR IDENTIFICATION OF THE END-TRIASSIC EXTINCTION AND THE TRIASSIC-JURASSIC BOUNDARY WITHIN THE COLORADO PLATEAU

Paper number: T12-6
Program: Technical Sessions
Time: 9:05 AM – 9:20 AM

Authors

Abstract

The end Triassic extinction (ETE) is one of the largest mass extinction events of the Phanerozoic, and it has been hypothesized that this event, as well as the Triassic-Jurassic (TJ) boundary, are preserved within the Moenave Formation of the Colorado Plateau. Identification of this boundary within the Colorado Plateau region is critical for better understanding of the relationship between climate change and the ETE in terrestrial, low latitude paleoenvironments. The Moenave Formation is well exposed in Blacks Canyon of Zion National Park and in the nearby Warner Valley, where detailed sedimentologic observations and Carbon isotope sampling have been conducted. Chemostratigraphic correlation of the bulk organic carbon (δ13Corg) (this study) with carbonate Carbon (δ13CCO3) and Oxygen isotope chemostratigraphy, detrital zircon U-Pb geochronology, and biostratigraphy provide new constraints on the location of the Triassic-Jurassic boundary and the ETE within the Moenave Formation. Samples were collected in 25cm increments in finer grained units and 50cm increments in thick sand units. Samples were then crushed, decarbonated, and analyzed for bulk Carbon on a Thermo Advantage Plus Isotope Ratio Mass Spectrometer (IRMS) via combustion in an elemental analyzer. This study hypothesizes that the negative carbon isotope excursion associated with the ETE will occur in the lower Dinosaur Canyon Member (DCM), and the TJB will occur higher in the section in the middle to upper DCM. The location of these boundary events along with field- and drone-based observations and measurements will quantify the impact of climatic warming during the Late Triassic-early Jurassic boundary by relating sedimentologic observations to palaeohydrologic processes. Initial observations suggest that there is an observable stratigraphic change in sedimentation in the fluvial DCM, with a trend toward increasing channelization upwards in the DCM. This research is thus expected to yield insights into the sedimentologic and hydrologic response to modern or future climatic warming events similar to the magnitude of the ETE and the TJ boundary.

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

doi: 10.1130/abs/2019AM-340357

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