Uplift of the Central Andes of NW Argentina associated with upper crustal shortening, revealed by multiproxy isotopic analyses

Barbara Carrapa,Mark Clementz,Katharine W Huntington,Lindsay M Schoenbohm,Sharon Bywater-Reyes,Robin R Canavan,Jay Quade

doi:10.1002/2013tc003461

Abstract

This study contributes to the uplift history of the Andes, which has received increasing attention in recent years because of its implications for geodynamic models and climate feedbacks. Shortening resulting in crustal thickening and removal of gravitationally unstable mantle lithosphere has been proposed to control deformation and uplift of Cordillera-type orogenic systems such as the Puna Plateau of the central Andes and its eastern margin, the Eastern Cordillera. We present new clumped isotope (Δ47), δ18O, and δ2Η data from carbonate nodules, marlstone, spring deposits, and volcanic ashes from the Puna Plateau and Eastern Cordillera of NW Argentina. When combined with other geological evidence, our data indicate that the Puna Plateau was near its present elevation since at least ~10 Ma, whereas the Eastern Cordillera rose ~1.5 km between ~14 and ~7 Ma. This history of uplift correlates with active shortening in the Eastern Cordillera and with incorporation of a regional foreland into the propagating orogenic wedge. Our study suggests that the elevation of the Puna Plateau changed little during the Miocene-Pliocene, whereas the margin experienced significant uplift associated with active deformation and crustal thickening.

Highlights

The Andes is a Cordillera-type orogenic system in which subduction of the oceanic Nazca plate under the continental South American plate has controlled a variety of processes such as magmatism, lithospheric removal, subduction, erosion and accretion, and shortening and crustal thickening [e.g., Kley and Monaldi, 1998; Haschke et al, 2002; Melnick and Echtler, 2006]
Our study suggests that the elevation of the Puna Plateau changed little during the Miocene-Pliocene, whereas the margin experienced significant uplift associated with active deformation and crustal thickening
Using the fractionation factor between the δ2H value of volcanic glass and of meteoric water (1.0343 [Friedman et al, 1993]), corresponding δ2H meteoric water values (δ2Hmw) for the Puna Plateau and Eastern Cordillera samples are calculated to have been around À70‰ and À45‰, respectively

Summary

Introduction

The Andes is a Cordillera-type orogenic system in which subduction of the oceanic Nazca plate under the continental South American plate has controlled a variety of processes such as magmatism, lithospheric removal, subduction, erosion and accretion, and shortening and crustal thickening [e.g., Kley and Monaldi, 1998; Haschke et al, 2002; Melnick and Echtler, 2006]. A cyclical relationship between lithosphere removal, magmatism, deformation, and surface uplift has been proposed to govern Cordillera-type orogenic systems [DeCelles et al, 2009]. According to this model, melt-fertile lower crust and upper mantle is underthrust beneath the arc, initiating melting and fractionation, which forms a dense (eclogitic) root. Regional uplift initiates outward propagation of the flanking orogenic wedges, upper crustal extension, and igneous flare-up. The cycle begins again, with renewed underthrusting In this model, shortening and crustal thickening are the key preconditions to initiate lithospheric instabilities and removal. The model makes useful predictions about what is required for lithospheric removal to happen; the expected magnitude of elevation changes during shortening and crustal thickening and following root removal remain largely unconstrained due to the uncertainties related to shortening estimates and volume of lithosphere removed

Methods

Results

Discussion

Conclusion