Browsing by Author "Kragh, Natali Ann"

Now showing 1 - 1 of 1

Addressing the state of Yellowstone National Park's geologic maps using traditional and novel approaches
(Montana State University - Bozeman, College of Letters & Science, 2023) Kragh, Natali Ann; Chairperson, Graduate Committee: Madison Myers
Accurate geologic mapping is especially important for public land, such as Yellowstone National Park, so land managers can mitigate safety risks, mindfully place infrastructure, and communicate scientific knowledge to the public. The geology of Yellowstone National Park (YNP) has been repeatedly mapped over the last century by multiple geologists with varying perspectives and mapping goals. The most recent efforts have resulted in a patchwork of twenty-one different scale maps (one 1:125,000, one 1:100,000, and nineteen 1:62,500). Presently, there exists significant promise of publishing a higher resolution, seamless map of YNP; however, it has become apparent that many of the current internal maps disagree along their shared boundaries. This study aims to address these discrepancies using both traditional and novel techniques and determine if mapping along boundaries is the best practice towards creating a seamless map. In total, 485 areas of disagreement, referred to here as boundary problems, were identified. During this study, 66 boundary problems were resolved. Each resolved boundary problem was aided by traditional mapping techniques (i.e., field mapping, field petrography, sample collection, and limited geochemistry and thin section work). However, some areas could not be addressed by field methods alone and required a more substantial analytical approach. Three "case studies" were chosen to highlight how geochemistry could aide in mapping in YNP: 1) a geochemical, textural, and age analysis of "dacite" units found throughout the north and northwestern portions of YNP and the Greater Yellowstone Region, 2) compiling a geochemical database to compare and correlate known rock units to unrecognized outcrops found in the field, 3) a novel technique using Pb isotopes in detrital plagioclase crystals from volcaniclastic units to establish a volcanic source for the units. These approaches resulted in varying success, but overall, lead to a better understanding of the work that needs to be done in YNP to publish an accurate, higher resolution geologic map. This work highlights the importance of reassessing older geologic maps and making necessary updates when the need is recognized, particularly along disagreeing shared boundaries using multiple techniques.