T250 The Andes from Top to Bottom (Posters)

Wednesday, 18 October 2023
8:00 AM - 5:30 PM
Hall B

TOWARD A DETAILED 4D RECONSTRUCTION OF BASIN GEOMETRY, SEDIMENT PROVENANCE, AND TECTONIC-GEODYNAMIC SUBSIDENCE DRIVERS IN THE CENTRAL ANDEAN ALTIPLANO

Paper number: T250-6
Program: Technical Sessions
Time: 8:00 AM – 5:30 PM

Authors

Abstract

We synthesize new and published detrital zircon (DZ) U-Pb data from Upper Cretaceous-Cenozoic strata in the central Andes’ Altiplano Basin (AB) to evaluate tectonic models of this classic Cordilleran orogen. The locus and pace of subsidence is a key discriminator of tectonic setting, subsidence mechanisms, and forces involved in orogenesis. For example, in the AB, rapid subsidence would be expected to progress west to east in a foreland setting with a load exclusively to the west, whereas synchronous subsidence across strike and an influx of Eastern Cordilleran (EC) sediment would suggest hinterland deposition following a proposed eastward jump in contractional deformation to the EC and resultant loads both to the east and west. Moreover, recent DZ work in the northern AB suggests the jump in deformation and foreland-hinterland transition progressed north to south.

Despite these distinct predictions, remaining gaps in DZ data coverage hinder understanding of basin evolution and its tectonic context, including whether subsidence occurred in a foreland or hinterland setting and how the spatio-temporal distribution of changes in subsidence rate compares to the shortening history. DZ data are currently unavailable for most of the west-central and southern AB; data in these geographic gaps are needed to determine the overall basin response to orogenesis and to inform potential mechanisms.

We present new DZ-based maximum depositional ages (MDAs) and provenance data from stratigraphic sections in the western and southern AB, allowing us to discriminate synchronous versus asynchronous changes throughout the entire basin. To elucidate across-strike variation in subsidence history and sediment sources, we compare DZ MDAs and mixture modeling results for the western limb of the central AB’s Corque Syncline to its eastern limb, where the onset of rapid sediment accumulation is well-established based on DZ MDAs and magneto-stratigraphy. We also compare the central AB record to published DZ data from the northern AB and new DZ data from the southern AB. Along- and across-strike synthesis of these datasets provides a new 4D perspective on drivers of central Andean orogenesis and associated basin formation.

Geological Society of America Abstracts with Programs. Vol. 55, No. 6

doi: 10.1130/abs/2023AM-390351

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