60-60 Paleocurrent Analysis and Preliminary Facies Architecture within a channel belt sandstone in the Upper Triassic Dockum Group, Southern Garza County, TX USA

Session: 2YC and 4YCU Geoscience Student Research Poster Showcase

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Authors:

Abstract:

Paleocurrent Analysis and Preliminary Facies Architecture within a channel belt sandstone in the Upper Triassic Dockum Group, Southern[SH1]  Garza County, TX USA

Zachary H Robinson⁽¹⁾, Dr. Jeffrey W. Martz⁽²⁾, and Dr. Sarah N. Heinlein⁽¹⁾

Angelo State University, Department of Physics and Geosciences, San Angelo, TX. USA⁽¹⁾

The Museum of Texas Tech University, Lubbock, TX. USA⁽²⁾

Abstract

The Dockum Group of western Texas is an Upper Triassic fluvio-lacustrine unit known for its rich vertebrate fossil record. Understanding its depositional systems is essential for reconstructing the relationship between changing paleoenvironments and vertebrate ecology. There have been few facies analyses and paleosol studies of the Dockum Group. Our project area is located in southern Garza County in northwestern Texas. We employ facies analysis to investigate the depositional system of the Dalby Ranch sandstone in the Trujillo Formation. This sandstone is predominantly medium-grained and compositionally immature. The unit is dominated by upper flow regime horizontal planar beds and lower flow regime tabular and trough crossbedding. There are also numerous internal scours and minor ripple cross-lamination. Intrabasinal conglomerate occurs at the base of the outcrop. The sedimentary structures indicate repeating high-flow regime conditions followed by decreasing water velocity, consistent with the highly variable flow documented in the Trujillo Formation elsewhere. Paleocurrent directions are predominantly to the northeast, consistent with derivation from the Ouachita-Marathon Orogenic Belt. It is not yet clear if accretion was lateral or downstream, although the concentration of conglomeratic beds low in the outcrop suggest thalweg deposits. Finer-grained overbank deposits above and below the Dalby Ranch sandstone contain drab mottling, but little paleosol development, suggesting high deposition rates.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-9237

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