UNDERSTANDING OUR SPECTACULAR MOUNTAIN LANDSCAPES: A HELIUM THERMOCHRONOLOGY STUDY IN ROCKY MOUNTAIN NATIONAL PARK

Many of the most impressive and iconic mountain landscapes in the United States are protected under the National Park System, including Rocky Mountain, Yosemite, Grand Teton, Denali, and Glacier National Parks. These landscapes are awe-inspiring for millions of visitors, in large part due to their geology. However, mountain landscapes are also some of the most threatened by human activity, and therefore it is imperative to instill a sense of respect and stewardship in those who visit. Understanding how those landscapes formed is a key approach to cultivating these values in visitors. Fortunately, visitors are drawn to mountains for a number of reasons – recreation, beauty, solitude, etc. – and thus are typically predisposed to be interested in understanding the geologic story behind those mountains. Rocky Mountain National Park in the Front Range of northern Colorado is an exceptional place for geologists to interact with the public on the subject of mountain landscapes. The park has a rich geologic history extending back 1.7 billion years that is spectacularly manifested as 72 peaks soaring 12,000 feet (3,700 m) or higher above sea level. Furthermore, it is one of the most visited national parks in the country, hosting an average of 3 million visitors per year. Despite the prominence of this mountain landscape, little is known of its history between the three major mountain-building events that affected this area, occurring in the Proterozoic (~1750 Ma), Pennsylvanian (~300 Ma), and Laramide (~65 Ma). Helium (U-Th/He) thermochronology is an approach that allows one to investigate the thermal histories of rocks – how they cooled as erosion brought them to the surface – and gain insight into topographic and landscape evolution. Samples were collected in the Lumpy Ridge and Mount Ida areas of Rocky Mountain N.P. as part of a broader thermochronology study in the Front Range. By utilizing several different minerals (apatite, zircon, titanite), we can better understand now enigmatic portions of the region’s geologic history. In addition to addressing this billion-year knowledge gap, we intend for this research to serve as an important bridge between scientific research, the park visitors, the mountains they travelled to see, and the driving mission of the National Park Service to preserve these special landscapes.