12 Tectonics in the Rocky Mountain Region from the Precambrian to the Quaternary (Posters)

Tuesday, 5 May 2020
8:30 AM - 4:30 PM
Ballroom A

THERMOCHRONOLOGY LINKS GROWTH OF THE ROCKY MOUNTAIN FRONT RANGE TO INVERSION OF A NEOPROTEROZOIC RIFT SYSTEM

Paper number: 12-4
Program: Theme Sessions
Time: 8:30 AM – 4:30 PM

Authors

Abstract

Localization of Phanerozoic deformation in the Southern Rocky Mountains (USA) has been hypothesized to reflect reactivation of a Proterozoic rift system formed during the breakup of the supercontinent Rodinia. The inference that orogenic deformation in continental interiors may be controlled by ancient structures is geologically compelling; however, clear evidence supporting such a linkage is commonly sparse. We document the Neoproterozoic-Recent tectonic history of Paleoproterozoic crystalline rocks in Colorado’s Front Range through thermal history modeling of zircon (U-Th)/He (He) thermochronologic ages that range from 50-607 Ma and vary as a function of crystal U-Th composition (i.e., radiation damage). Contacts between the crystalline rocks and Neoproterozoic and Paleozoic sedimentary rocks provide unique constraints that place our samples near Earth’s surface (<2 km depth) at ca. 700, 500, and 300 Ma. Thermal histories that reproduce the zircon He ages require heating to >250˚C (324±20˚C) and then cooling to <60˚C during late Neoproterozoic time. We argue that these results document the origin of the Front Range as a zone of rifting that experienced km-scale burial and exhumation coeval with Neoproterozoic fragmentation of western Laurentia and concurrent global glaciations.

Geological Society of America Abstracts with Programs. Vol. 52, No. 3

doi: 10.1130/abs/2020RM-346465

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