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Low-temperature thermochronologic trends across the central Andes, 21°S–28°S

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P.W. Reiners
P.W. Reiners
Department of Geosciences, University of Arizona, 1040 E. 4th Street, Tucson, Arizona 85721, USA
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S.N. Thomson
S.N. Thomson
Department of Geosciences, University of Arizona, 1040 E. 4th Street, Tucson, Arizona 85721, USA
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A. Vernon
A. Vernon
Department of Geosciences, University of Arizona, 1040 E. 4th Street, Tucson, Arizona 85721, USA
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S.D. Willett
S.D. Willett
Geologisches Institut, Eidgenössische Technische Hochschule, NO E 33, Sonneggstrasse 5, 8092 Zürich, Switzerland
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M. Zattin
M. Zattin
Department of Geosciences, University of Padova, 35137 Padova, Italy
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J. Einhorn
J. Einhorn
Department of Geosciences, University of Arizona, 1040 E. 4th Street, Tucson, Arizona 85721, USA
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G. Gehrels
G. Gehrels
Department of Geosciences, University of Arizona, 1040 E. 4th Street, Tucson, Arizona 85721, USA
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J. Quade
J. Quade
Department of Geosciences, University of Arizona, 1040 E. 4th Street, Tucson, Arizona 85721, USA
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D. Pearson
D. Pearson
Department of Geosciences, University of Arizona, 1040 E. 4th Street, Tucson, Arizona 85721, USA
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K.E. Murray
K.E. Murray
Department of Geosciences, University of Arizona, 1040 E. 4th Street, Tucson, Arizona 85721, USA
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W. Cavazza
W. Cavazza
Dipartimento di Scienze, Biologiche, Geologiche e Ambientali, Università di Bologna, 40126 Bologna, Italy
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Published:
January 01, 2015

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°S and 28°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 ~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.

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GSA Memoirs

Geodynamics of a Cordilleran Orogenic System: The Central Andes of Argentina and Northern Chile

Peter G. DeCelles
Peter G. DeCelles
Department of Geosciences, University of Arizona, Tucson, Arizona, USA
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Mihai N. Ducea
Mihai N. Ducea
Department of Geosciences, University of Arizona, Tucson, Arizona, USA, and Universitatea Bucuresti, Facultatea de Geologie Geofizica, Strada N. Balcescu Nr 1, Bucuresti, Romania
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Barbara Carrapa
Barbara Carrapa
Department of Geosciences, University of Arizona, Tucson, Arizona, USA
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Paul A. Kapp
Paul A. Kapp
Department of Geosciences, University of Arizona, Tucson, Arizona, USA
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Geological Society of America
Volume
212
ISBN print:
9780813712123
Publication date:
January 01, 2015

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