An Overview
Program: RESESS Boulder
Major: Environmental Studies
Academic Affiliation: University of Colorado Boulder
Mentors: Dr. Lon Abbott, Dr. Rebecca Flowers
Biography
Skye Fernandez is pursuing her Bachelor’s at the University of Colorado Boulder with a major in Environmental Studies and a minor in Political Science. Her 2021 RESESS project is focused on understanding the timing of exhumation from the Spanish Peaks and Front Range region of Colorado to southeastern Colorado by using radiometric dating and low temperature thermochronology. She hopes to pursue a future in conservation and public policy. She spends her free time painting, writing, and playing ultimate frisbee.
Abstract
The Southern Rocky Mountains of Colorado and New Mexico were initially raised from sea level during deformation associated with the Laramide Orogeny ~70-45 Ma; but it is widely agreed that the range later experienced a cryptic, post-Laramide episode of surface uplift that occurred in the absence of short-wavelength deformation. Adjacent portions of the Great Plains that currently stand higher than 1800 m were also at sea level just prior to the Laramide Orogeny; considering their lack of deformation, when and how they were uplifted is enigmatic. Apatite (U-Th)/He (AHe) thermochronologic dates and associated thermal modeling constrain a rock’s time-temperature path through its last 1.5-2 km of exhumation. Although an exhumation event can have causes other than surface uplift, when other potential causes are carefully considered and can be ruled out, that exhumation history can serve as a proxy for the timing of regional surface uplift. Previous AHe studies have documented Eocene (>45 Ma) exhumation in the Front Range region of northeastern Colorado and later, Oligo-Miocene exhumation (~25-8 Ma) in the Spanish Peaks area of southeastern Colorado. One must ask: ‘Why is there a temporal difference in exhumation between northeastern Colorado and the Spanish Peaks area?’ A further question is: ‘How large is the footprint of the Spanish Peaks exhumation event?’ We examined samples from the Great Plains of southeastern Colorado and northeastern New Mexico to determine how far east the Spanish Peaks ~25-8 Ma exhumation event extends. Our initial results document a 6 Ma AHe date for a lamprophyre dike likely emplaced ca. 25 Ma and located ~55 km northeast of the Spanish Peaks. We will present AHe dates for this and our remaining samples, thus exploring the footprint of the Spanish Peaks exhumation event to distances of 200 km east, 150 km south, and 50 km north of the Spanish Peaks.