--> Provenance Evolution of Paleocene-Miocene Guadalupe-Live Oak Deltas in South Texas: Insights From Detrital Zircon Geochronology

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Provenance Evolution of Paleocene-Miocene Guadalupe-Live Oak Deltas in South Texas: Insights From Detrital Zircon Geochronology

Abstract

The Guadalupe-Live Oak deltas in South Texas served as important sediment pathways for sediment eroded from source area entering into the deep-water Gulf of Mexico and archived important provenance changes from Paleocene to Miocene. In order to decipher the linkage between the provenance changes in the source and sediment accumulation in the basin, we use 1419 zircon U-Pb ages analyzed from 12 samples across the Guadalupe-Live Oak deltas in South Texas, of which 1206 ages from 10 samples are unpublished new data. The detrital zircon results demonstrate four drainage systems from Paleocene to Miocene. (1) Six Paleocene-Eocene Wilcox Group samples show an overall consistent pattern and are dominated by U-Pb ages of < 0.3 Ga (34.1%-58.3%) and 1.3-1.8 Ga (26%-44.7%), with 0.3-1.3 Ga (5.9%-14.7%) and >1.8 Ga (0-8.1%) as minor components, suggesting major sediment sources from Western Cordillera Arc and Laramide Uplifts. (2) Two Early Eocene Queen City and Yegua Formation samples show a rapid increase of 0.3-1.3 Ga components in relative to the underlying Paleocene-Eocene Wilcox Group samples, which likely indicate a recycling of Triassic-lower Cretaceous strata in the Sevier foreland basin. (3) One Late Eocene Jackson sandstone shows a dramatically different age distribution pattern than both underlying and overlying samples, with nearly 80% and 30% of zircon ages younger than 300 Ma and 40 Ma, respectively. This usually age pattern strongly indicates a flux of volcanic ash during the late Eocene. (4) Three latest Oligocene-middle Miocene samples are dominated by < 300 Ma age component (45.9-59.7%), with age components of 0.3-1.3 Ga (16.8-26.6%) and 1.3-1.8 Ga (22.7%-25.7%) as secondary components. Given the relatively high similarity of U-Pb age patterns between the latest Oligocene-middle Miocene and older updip sedimentary strata (e.g., Wilcox strata) and the rifting of Rio Grande, the sediments are largely recycled from the sedimentary strata stored on the Great Plains that were uplifted due to the Mid-Cenozoic magmatism during this time. Four stages of drainage evolution showed by the detrital zircon age data from Guadalupe-Live Oak deltas clearly reveals regional tectonic evolution and magmatism in the southwestern North America.