High-Resolution Geochemistry and Petrography of a Miocene Succession From the Central Argentinian Foreland (Mendoza Province, Argentina): A Compositional Approach to Deciphering Forcing Factors

Abstract

Sediments deposited in foreland basins are accurate recorders of processes acting at different temporal and spatial scales during orogenic uplift; however uncertainties commonly remain in interpreting the effects of different allogenic factors on foreland sedimentation at a high-resolution, and in differentiating such effects from those of autogenic processes. Here, we present observations from continental successions of the Central Argentinian Foreland (Mendoza Province, Argentina), focusing on the Miocene synorogenic deposits of the Mariño and La Pilona Formations. The large-scale stratigraphic trend leads to interpret the system as a fluvial fan that prograded from the basin margin. The main objectives are: (1) to detect geochemical signatures of allogenic controls; (2) track changes in sediment provenance in relation to magmatism and exhumation of the uplifting Andes; and (3) recognize the effects of different allogenic drives on sedimentary processes; (4) testing the effectiveness of high-resolution chemostratigraphy for correlation within fluvial-fan successions along thick stratigraphic intervals. The approach embodies a high-resolution mineralogical and petrographic study, using automated QEMSCAN technology, heavy mineral analysis, geochemistry, radiogenic isotope analysis, and U-Pb dating of detrital zircons. Preliminary results on two outcrops mutually distant ∼10 km show the evolution of the sedimentary compositional signature. General trends common to both sections are recognized, reflecting the evolution of the system due to forcing factors acting at larger spatial and temporal scales. Isolated compositional signals proper to each section probably reflect spatial variations in processes. Vertical compositional changes through stratigraphy relate the progressive uplift of the Principal Cordillera. Eastward migration of the thrust front affected sediment compositions, with a contribution from detrital sources of the adjacent Frontal Cordillera. Quantitative measurements combined with stratigraphic correlations allow us to constrain the relative role of different forcing factors. This study also aims to offer insights into the understanding of comparable sedimentary successions in the subsurface. Besides providing an extensive outcrop analogue for the characterization and prediction of subsurface reservoirs, the project represents a ground-based assessment for mineralogical and geochemical methods of reservoir correlation and evaluation.

AAPG Datapages/Search and Discovery Article #90259 ©2016 AAPG Annual Convention and Exhibition, Calgary, Alberta, Canada, June 19-22, 2016