T49 Geodynamic, Orogenic, and Surface Processes of Flat-Slab Subduction (Posters)

Sunday, 4 November 2018
9:00 AM - 5:30 PM
Halls J-K

TRACKING DETRITAL ZIRCONS AND SEDIMENT MIXING IN MODERN EOLIAN SYSTEMS: EXAMPLE FROM THE ANDEAN BROKEN FORELAND BASIN OF ARGENTINA

Paper number: T49-4
Program: Technical Sessions
Time: 9:00 AM – 5:30 PM

Authors

Abstract

The use of detrital zircons to trace sediment provenance has increased exponentially due to technological advances in the efficiency and accuracy of U-Pb geochronology. Despite diverse applications of detrital zircon (DZ) U-Pb geochronology to ancient eolian deposits, few studies have evaluated dune fields in active depositional environments. Understanding sediment mixing in modern eolian systems is critical to connecting surface processes associated with tectonic and climatic processes in the stratigraphic record. Within this framework, we investigate how modern sediments contributed by the Rio San Juan, Rio Bermejo, and Rio Mendoza mix throughout the Medanos Grande, a modern dune field in the broken Andean foreland basin of west-central Argentina. Detrital zircon U-Pb results for 11 fluvial and eolian samples acquired using Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry provide a framework for evaluating the origin and progressive mixing of diverse source materials. Diagnostic age distributions help define the following source regions: (1) 1200-1000 Ma Sunsas basement and accreted Cuyania terrane; (2) 700-550 Ma eastern Sierras Pampeanas; (3) 550-400 Ma Pampean basement and Famatinian magmatic arc; (4) 340-280 Ma Carboniferous magmatic arc; (5) 280-240 Ma Choiyoi igneous province; and (6) 50-0 Ma Andean magmatic arc. A quantitative analysis of these U-Pb results reveal unique provenance signatures for individual rivers, whereas the eolian sediments in the Medanos Grande are well mixed, with a broad range of age populations. Tracking proximal-to-distal and fluvial-to-eolian signals throughout Medanos Grande provides insights into provenance trends in relationship to source proximity, sediment mixing, and contrasting mechanisms of sediment transport and deposition. This study offers modern analogs for eolian systems, broken foreland basins, and flat-slab tectonic regimes in ancient settings, enabling improved reconstructions of ancient tectonic and climatic processes.

Geological Society of America Abstracts with Programs. Vol. 50, No. 6

doi: 10.1130/abs/2018AM-322719

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