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Low-temperature thermochronologic trends across the Central Andes, 21 degrees S-28 degrees S

P. W. Reiners, Stuart N. Thomson, A. Vernon, S. D. Willett, M. Zattin, J. Einhorn, George E. Gehrels, Jay Quade, D. Pearson, Kendra E. Murray and W. Cavazza
Low-temperature thermochronologic trends across the Central Andes, 21 degrees S-28 degrees S
Memoir - Geological Society of America (2015) 212: 215-249

Abstract

In this paper, we merge more than 200 new apatite and zircon (U-Th)/He analyses and 21 apatite fission-track analyses from 71 new samples with previous published thermochronologic data using the same systems to understand the growth and large-scale kinematics of the central Andes between 21 degrees S and 28 degrees S. In general, minimum dates decrease and the total range of dates increases from west to east across the range. Large variations in thermochronometer dates on the east side reflect high spatial gradients in depth of recent erosional exhumation. Almost nowhere in this part of the Andes has Cenozoic erosion exceeded approximately 6-8 km, and in many places in the eastern half of the range, erosion has not exceeded 2-3 km, despite these regions now being 5-6 km above sea level. This means that west of the rapidly deforming and eroding eastern range front, uplift and erosion are largely decoupled as a result of meager precipitation, relatively low relief, internal drainage, and volcanic burial. We interpret the west-to-east pattern of decreasing minimum dates across the range as recording the time-transgressive eastward migration of a focused zone of deformation, erosion, and convergence between the South American plate and the eastern edge of the Andean orogenic plateau. At this scale, the thermochronologic data do not suggest major changes in rates of plateau propagation or shortening/convergence with time. We use the thermochronometer date-distance trend and a simple kinematic model to infer a rate of eastward propagation of deformation and plateau growth of 6-10 km/m.y. This plateau propagation model balances horizontal convergence, erosion, and crustal thickening and predicts rates of shortening and convergence between the Andes block and South American plate that are consistent with geologic and geodetic observations.


ISSN: 0072-1069
Coden: GSAMAQ
Serial Title: Memoir - Geological Society of America
Serial Volume: 212
Title: Low-temperature thermochronologic trends across the Central Andes, 21 degrees S-28 degrees S
Affiliation: University of Arizona, Department of Geosciences, Tucson, AZ, United States
Pages: 215-249
Published: 2015
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 95
Accession Number: 2015-036120
Categories: Geochronology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 3 tables, sketch map
S28°00'00" - S21°00'00", W75°00'00" - W63°00'00"
Secondary Affiliation: Eidgenoessische Technische Hochschule Zuerich, CHE, SwitzerlandUniversity of Padova, ITA, ItalyUniversita di Bologna, ITA, Italy
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201517
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