GSA Annual Meeting in Seattle, Washington, USA - 2017

Paper No. 43-7
Presentation Time: 3:25 PM

TECTONOMORPHIC INFLUENCE ON SEDIMENT SOURCES AND PATHWAYS THROUGH WEST TEXAS: DETRITAL ZIRCON GEOCHRONOLOGY OF THE LATE CRETACEOUS-PALEOGENE TORNILLO BASIN, BIG BEND NATIONAL PARK


KORTYNA, Cullen D.1, STOCKLI, Daniel F.1, SHARMAN, Glenn R.2 and COVAULT, Jacob A.3, (1)Department of Geological Sciences, Jackson School of Geosciences, The University of Texas at Austin, 2275 Speedway Stop C9000, Austin, TX 78712, (2)Department of Geosciences, University of Arkansas, Fayetteville, AR 72701, (3)Bureau of Economic Geology, University of Texas at Austin, Austin, TX 78713, cdkortyna@utexas.edu

Spatiotemporal variations in tectonic style are expressed by evolving topography, and exert a primary control on how sediment is generated by erosion and transported from source-to-sink. During Late Cretaceous-Paleogene time, New Mexico and south and west Texas were situated in a transitional tectonomorphic landscape between nascent Laramide topography and the Mexican Cordillera. There is considerable uncertainty surrounding the nature of the Cretaceous-Paleogene sediment routing systems that dissected this region, including the course of paleo-rivers, their catchment extent, and their debouchment locations along the Gulf of Mexico. A better characterization of the drainage system is vital to estimating sediment delivery to the Gulf of Mexico, and, broadly, understanding source-to-sink sediment transfer in systems defined by distinct, evolving tectonomorphic provinces. Detrital zircon (DZ) U-Pb geochronology is used to determine sediment source terranes, evaluate sedimentary recycling, quantify catchment sizes, and estimate sediment fluxes. DZ U-Pb provenance results from Cretaceous-Paleogene fluvial sediments of the Tornillo Basin in west Texas consist of dominantly Late Cretaceous age modes with subordinate Paleocene, Jurassic, Permian and minor Silurian-Ordovician, 1.1, 1.4, and 1.7 Ga modes. The DZ age spectra also contain an Early Cretaceous “arc gap” consistent with western U.S. sources and inconsistent with sources in the western Mexican Cordillera. Rim/core age relationships show four rim/core clusters: late Cretaceous/Jurassic, Late Cretaceous/1.1-1.5 Ga, Permian/1.5-1.6 Ga and Ordovician/1.1 Ga. These DZ results suggest a more extensive paleo-catchment system for the Tornillo Basin than previously inferred, potentially sourced from well within the western U.S. Cordillera, and/or recycled from Jurassic and Cretaceous sediments in the Mexican Laramide belt (e.g., Sabinas uplift). The interplay of possible arc/basement and recycled sedimentary sources show that sediment input to the Tornillo Basin was controlled by evolving Laramide topography in the U.S. and Mexico. This provides valuable insight into source-to-sink systems situated in transitional tectonomorphic landscapes, and the complexity of establishing sediment sources in such highly variable terranes.