T123 GSA Sedimentary Geology Division/SEPM (Society for Sedimentary Geology) Student Research Poster Competition: Dynamics of Stratigraphy and Sedimentation (Posters)

Monday, 23 September 2019
9:00 AM - 6:30 PM
Hall AB, North Building

STRATIGRAPHIC ARCHITECTURE AND PROVENANCE OF THE CRETACEOUS CERRO BARCINO FORMATION, PATAGONIAN BROKEN FORELAND BASIN, SOUTHERN ARGENTINA

Paper number: T123-14
Program: Technical Sessions
Time: 9:00 AM – 6:30 PM

Authors

Abstract

The Las Plumas and Cerro Castaño members of the Cerro Barcino Formation comprise an anomalously coarse-grained interval within the widespread and dominantly fine-grained Cretaceous Chubut Group of the Patagonian broken foreland basin, Chubut Province, Argentina. The coarse-grained character and distal position of this stratigraphic interval may signal a change from a continuous to broken foreland basin setting. To address this hypothesis, we assess the provenance and depositional history of the upper Lower Cretaceous Las Plumas-Cerro Castaño succession. We employ a multifaceted provenance approach including detrital zircon U-Pb geochronology, conglomerate clast counts, and sandstone petrography. Detailed unit descriptions, correlated stratigraphic sections, and detrital zircon U-Pb maximum depositional ages are used to refine the regional chronostratigraphic framework. Our results indicate maximum depositional ages of 107.4 ± 0.86 Ma (Albian) for the Cerro Castaño Member and 107.6 ± 1.2 Ma (Albian) and 96.2 ± 1.5 Ma (Cenomanian) for the Las Plumas Member. Provenance results indicate a polarity reversal from a west-derived Andean sediment source (<145 Ma) during deposition of the Cerro Castaño Member to east-derived intrabasinal basement-uplift sources (~188-177 Ma and >300 Ma) during deposition of the Las Plumas Member. This switch in dominant detrital age populations is accompanied by a change in depositional environment from fine-grained fluvial-lacustrine to conglomeratic braided fluvial conditions. We conclude this late-Early Cretaceous shift in sedimentary provenance signals foreland basin partitioning by basement-involved uplift during earliest Andean shortening.

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

doi: 10.1130/abs/2019AM-337544

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