Critical zone evolution<subtitle>Climate and exhumation in the Colorado Front Range</subtitle>

Abstract

The architecture of the critical zone—the distribution of mobile regolith, the thickness of weathered rock, and their characteristics, as well as the topography of the land surface—is shaped by erosion and weathering processes that depend upon both lithology and climate. In this trip we explore the Boulder Creek watershed, a landscape that juxtaposes uplifted Precambrian crystalline rocks of Colorado’s Front Range against Mesozoic marine sedimentary rocks underpinning the western edge of the High Plains. The landscape is strongly shaped by Quaternary climate cycles operating on this template inherited from the Laramide orogeny. Stop 1 will provide an overview of the abrupt topographic step at the Front Range–High Plains join, where we will discuss fl uvial strath terraces on the Plains. At Stop 2 in Betasso Preserve, we will discuss the impact of the canyon cutting set off by late Cenozoic exhumation of the High Plains on the hillslopes and groundwater systems lining the master stream. At Stop 3, we will hike 2 miles down Gordon Gulch, a focus site in the Boulder Creek Critical Zone Observatory. At stops on the hike, we will discuss exhumation rates, climate-modulated weathering, hillslope hydrology and hillslope sediment transport, and the infl uence of slope aspect on these processes. Our goal is to focus on the history of climate-driven erosion and weathering processes, and how to incorporate these processes into quantitative models of landscape evolution. Anderson, S.P., Anderson, R.S., Tucker, G.E., and Dethier, D.P., 2013, Critical zone evolution: Climate and exhumation in the Colorado Front Range, in Abbott, L.D., and Hancock, G.S., eds., Classic Concepts and New Directions: Exploring 125 Years of GSA Discoveries in the Rocky Mountain Region: Geological Society of America Field Guide 33, p. 1–18, doi:10.1130/2013.0033(01). For permission to copy, contact editing@geosociety.org. ©2013 The Geological Society of America. All rights reserved. CELEBRATING ADVANCES IN GEOSCIENCE 1888 2013 on June 26, 2014 fieldguides.gsapubs.org Downloaded from