Undergraduate Honors Theses

Thesis Defended

Spring 2016

Document Type

Thesis

Type of Thesis

Departmental Honors

Department

Geological Sciences

First Advisor

Robert S. Anderson, PhD.

Second Advisor

Suzanne P. Anderson, PhD.

Third Advisor

Charles R. Stern, PhD.

Fourth Advisor

Gifford H. Miller, PhD.

Abstract

Late Pleistocene glaciations of the Sawatch and Elk Mountain Ranges of Central Colorado at ~130 and ~20 ka left behind glacial features in the topography, ideal for constraining the local climactic variability. In the northern end of the Sawatch Range, distinct lateral and terminal moraines reveal strong geologic evidence that multiple large glaciers drained eastward. Two of these appear to have dammed the Arkansas River. Very fine-grained lacustrine sediments, ‘ice-rafted’ boulders, and catastrophic glacial flood boulders down-valley, show at least two glacial-ice dammed lakes that catastrophically drained. We report flood discharge calculations consistent with previous estimates, on the order of ~50,000 m3/s. For this study, we employ a 1-D finite difference staggered-grid mass conservation numerical model to reconstruct paleoglacier extent and equilibrium line elevations. I prescribe a mass balance based on a scaled approximation of the marine δ18O record, with normally distributed random number generation. Modeled ELA’s on the order of ~3400 m are consistent with temperature depressions nearly ~6 ºC below the modern mean annual air temperature. Our model shows internal consistency with the dependence of catchment geometry and variable metrological forcing on glacier disequilibrium response time. In the West Elk Mountains lies Snowmass Creek Valley, where at ~20 ka the ice extent is required to have preserved the famous Ziegler Reservoir paleontological site. Employing our 1-D numerical model on this site, for the climate at ~20 ka, reveals that the required temperature depression is on the order of ~1ºC warmer than it was during the Bull Lake glaciation at ~130 ka.

glacial_code_4_4_16.pdf (2236 kB)
glacial script written in MATLAB

discharge_code_4_3_16.pdf (769 kB)
discharge script written in MATLAB