CALL FOR PROPOSALS:

ORGANIZERS

  • Harvey Thorleifson, Chair
    Minnesota Geological Survey
  • Carrie Jennings, Vice Chair
    Minnesota Geological Survey
  • David Bush, Technical Program Chair
    University of West Georgia
  • Jim Miller, Field Trip Chair
    University of Minnesota Duluth
  • Curtis M. Hudak, Sponsorship Chair
    Foth Infrastructure & Environment, LLC

 

Paper No. 13
Presentation Time: 12:00 PM

DEVELOPMENT OF A 3-DIMENSIONAL SEQUENCE STRATIGRAPHIC MODEL FOR THE LATE TRIASSIC (NORIAN) OWL ROCK MEMBER LOCATED AT PETRIFIED FOREST NATIONAL PARK, ARIZONA: A RECONSTRUCTION OF PALEODEPOSITIONAL ENVIRONMENTS AND PALEOCLIMATIC CONDITIONS


FELDA, Garrett Robert, Baylor University, Department of Geology, Waco, TX 76706, garrett_felda@baylor.edu

This research focuses on building the first comprehensive sequence stratigraphic model for the late Triassic (Norian) Owl Rock Member (Chinle Formation) exposed at Chinde Mesa within the northern boundary of Petrified Forest National Park (PEFO), Arizona. The model is used to characterize temporal and spatial distributions of alluvial and lacustrine facies based on outcrop observations, and interpret deviations in associated depositional environments through stacking pattern analysis.

Alluvial depositional cycles within the Chinle Formation at PEFO have previously been recognized as being organized within a cyclic hierarchy of meter-scale fluvial aggradational cycles (FAC’s), decameter-scale fluvial aggradational cycle sets (FAC-sets), and deca- to hectometer-scale fluvial sequences. FAC’s occur as either fining-upward terrestrial deposits that have a paleosol weathered into their upper boundary, or have an upper boundary that lacks a paleosol and is abruptly overlain by coarser-grained deposits of the overlying FAC. Measured sections of the Owl Rock Member at Chinde Mesa are accompanied by map-oriented, high-resolution, digital photopans that highlight the distribution of FAC surfaces and inferred fluvial architectural elements.

The interplay between sedimentation and climate during the time interval preceding the Triassic-Jurassic biotic crisis is also examined in this study. Important climatic factors considered include atmospheric carbon dioxide concentrations (based on stable carbon isotope analysis of pedogenic carbonate), and mean annual temperatures (based on stable oxygen isotope analysis of both pedogenic and lacustrine carbonate). Carbonate specimens collected along measured sections are evaluated in terms of isotopic reliability using petrographic microscopy. Calculated atmospheric carbon dioxide concentrations and mean annual temperatures are compared to elucidate temporal relationships.

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