Geological Society of America

12 Directly Dating Deformation, Metamorphism, and Metasomatism through Petrochronology II

Tuesday, 15 March 2022
1:30 PM - 5:30 PM
CBC-A 112

LATE CENOZOIC FOUNDERING OF MANTLE LITHOSPHERE IN THE WESTERN CORDILLERA OF SOUTHERN PERU

Paper number: 12-8
Program: Theme Sessions
Time: 3:25 PM – 3:45 PM

Authors

Ryan Eden Presenting Author
University of California, Santa Barbara, Santa Barbara, CA
Kurt E. Sundell
Idaho State University, Pocatello, ID
George E. Gehrels
University of Arizona, Tucson, AZ
Joel E. Saylor
University of British Columbia, Vancouver, BC

Abstract

The relationship between surface uplift and crustal thickening in the building of extreme (>3 km) elevation in the central Andes is debated. End member hypotheses include (1) coupled pure shear crustal thickening and concomitant slow (i.e., km/10’s Myr) surface uplift; and (2) decoupled crustal thickening and rapid (i.e., km/Myr) surface uplift driven by foundering of mantle lithosphere. We tested these with new laser ablation ICP-MS Lu-Hf isotopic analysis of zircons sampled from ignimbrite deposits in Oligocene – Miocene hinterland basins in the Western Cordillera of southern Peru, interpreted in the context of igneous whole rock geochemical data. Pulsed juvenile magmatism is roughly coeval with a transition in hinterland basin deposition, from fluvial to evaporitic-lacustrine, and with recently reported rapid surface uplift between 22 and 10 Ma. Results support a decoupling between crustal thickening and surface uplift in the northern CAP during the late Cenozoic due to the formation and subsequent foundering of dense lower lithosphere via Rayleigh-Taylor instability, after protracted crustal thickening and shortening.

Geological Society of America Abstracts with Programs. Vol. 54, No. 2

doi: 10.1130/abs/2022CD-374327

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