TY - JOUR
T1 - Nonuniform surface uplift of the Andean plateau revealed by deuterium isotopes in Miocene volcanic glass from southern Peru
AU - Saylor, Joel E.
AU - Horton, Brian K.
N1 - Funding Information:
We thank Victor Carlotto (Instituto Geológico, Minero y Metalúrgico–INGEMMET and Universidad Nacional San Antonio Abad del Cusco), Carmala Garzione, and John Bershaw for beneficial discussions of field relationships and John Christian Arredondo Sosa, Boris Del Castillo Herrera, Justin Fitch, and Nicholas Perez for assistance in the field. Jaime Barnes, Dan Breecker, Elizabeth Cassel, and Toti Larson provided critical advice and training in sample processing and analytical procedures for the stable isotope laboratory at the University of Texas at Austin. Zachary Anderson, Jessica Jordan, and Raemy Winton assisted with zircon U–Pb geochronology. We thank Andrew Leier, two anonymous reviewers, and Editor Jean Lynch-Stieglitz for critiques that helped to strengthen the manuscript, and Nadja Insel and Chris Poulsen for constructive comments on earlier drafts. This research was supported by NSF grant EAR-0908518 .
Copyright:
Copyright 2013 Elsevier B.V., All rights reserved.
PY - 2014/2/1
Y1 - 2014/2/1
N2 - Proposals for rapid late Miocene surface uplift driven by large-scale lithospheric removal beneath the central Andean plateau have been based largely on temperature-sensitive paleoaltimeters. Both the magnitude and mechanism of this proposed pulse of uplift have been challenged. First, climatic general circulation models support protracted uplift with predicted temperature and isotopic shifts enhanced by attainment of threshold elevations. Second, tectonic models in which surface elevations are compensated by regional contraction and crustal thickening question the need for lithospheric removal and predict broadly coeval uplift of the entire plateau. We present hydrogen isotope data using a novel temperature-insensitive volcanic glass proxy from continuous, well-dated lower to middle Miocene basin fill in the Western Cordillera of the northern plateau that show a rapid decrease in δD values (-62.8‰) at 19-16 Ma, with extremely negative values continuing into the Pliocene. We propose that the basin reached its current elevation by 16 Ma, >6 Myr earlier than proposed for the central plateau. The rapid decrease in δD values is consistent with punctuated surface uplift of 2.2-3.7 km between 19 and 16 Ma. Whereas the 3.7 km upper estimate assumes a static climate similar to modern, the 2.2 km lower estimate conservatively incorporates modeled changes in the isotopic composition of precipitation associated with elevation change. Comparison of these results to existing paleoelevation estimates from the Andean plateau facilitates a tentative reconstruction of earliest middle Miocene paleotopography showing a central depression with flanking hinterland and thrust-belt highlands. This apparent pattern of nonuniform plateau uplift contradicts shortening-proportional topographic growth over tens of Myr. We propose that temporally and spatially irregular surface uplift may be linked to pronounced local variability in crustal shortening and/or piecemeal removal of dense mantle lithosphere. Insofar as these irregularities reflect the scale of heterogeneity for surface uplift processes, available paleoelevation estimates point to a principal uplift mechanism that varies over relatively short (<250 km) horizontal distances.
AB - Proposals for rapid late Miocene surface uplift driven by large-scale lithospheric removal beneath the central Andean plateau have been based largely on temperature-sensitive paleoaltimeters. Both the magnitude and mechanism of this proposed pulse of uplift have been challenged. First, climatic general circulation models support protracted uplift with predicted temperature and isotopic shifts enhanced by attainment of threshold elevations. Second, tectonic models in which surface elevations are compensated by regional contraction and crustal thickening question the need for lithospheric removal and predict broadly coeval uplift of the entire plateau. We present hydrogen isotope data using a novel temperature-insensitive volcanic glass proxy from continuous, well-dated lower to middle Miocene basin fill in the Western Cordillera of the northern plateau that show a rapid decrease in δD values (-62.8‰) at 19-16 Ma, with extremely negative values continuing into the Pliocene. We propose that the basin reached its current elevation by 16 Ma, >6 Myr earlier than proposed for the central plateau. The rapid decrease in δD values is consistent with punctuated surface uplift of 2.2-3.7 km between 19 and 16 Ma. Whereas the 3.7 km upper estimate assumes a static climate similar to modern, the 2.2 km lower estimate conservatively incorporates modeled changes in the isotopic composition of precipitation associated with elevation change. Comparison of these results to existing paleoelevation estimates from the Andean plateau facilitates a tentative reconstruction of earliest middle Miocene paleotopography showing a central depression with flanking hinterland and thrust-belt highlands. This apparent pattern of nonuniform plateau uplift contradicts shortening-proportional topographic growth over tens of Myr. We propose that temporally and spatially irregular surface uplift may be linked to pronounced local variability in crustal shortening and/or piecemeal removal of dense mantle lithosphere. Insofar as these irregularities reflect the scale of heterogeneity for surface uplift processes, available paleoelevation estimates point to a principal uplift mechanism that varies over relatively short (<250 km) horizontal distances.
KW - Altiplano
KW - Central Andean plateau
KW - Deuterium
KW - Paleoaltimetry
KW - Paleoelevation
KW - Stable isotope geochemistry
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U2 - 10.1016/j.epsl.2013.11.015
DO - 10.1016/j.epsl.2013.11.015
M3 - Article
AN - SCOPUS:84889593367
SN - 0012-821X
VL - 387
SP - 120
EP - 131
JO - Earth and Planetary Science Letters
JF - Earth and Planetary Science Letters
ER -