UPDATING AND ASSESSING THE ACCURACY OF THE GEOLOGIC MAPS OF YELLOWSTONE NATIONAL PARK

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-two different scale maps (one 1:125,000, one 1:100,000, nineteen 1:62,500, and one 1:24,000) and a compiled geologic map published at a 1:125,000 scale. Presently, there exists significant promise of publishing a higher resolution map of YNP; however, it has become apparent that many of the current internal maps disagree along their shared boundaries. These are referred to as boundary problems. Disagreements range from offset geologic contacts to units with contrasting descriptions abutting each other. Of the 485 defined boundary problems within YNP, 365 existed between maps of different scales (e.g., 1:100,000 map against a 1:62,500 map) while only 120 problems are between maps of the same scale. Here we outline the preliminary results of our ambitious mapping project to resolve these boundary problems. We found that the same-scale boundary issues are typically simple to resolve with a modest (~1 day) timeframe. In contrast, the different-scale boundary problems prove nearly impossible to resolve in a single field visit. Often these problems are the result of larger mapping disagreements that will require significant time to resolve (>3 weeks). Of the 48 sites visited thus far, our observations suggest that the largest hinderance to an updated, higher resolution map of YNP is the limitation of coarser scale maps. To further support this finding and establish mapping priorities for the future, we have applied a statistical approach to five quadrants to assess the accuracy of those internal maps. In addition, whole rock geochemistry and age dating is used to resolve naming and unit identification conflicts. Ultimately, this research will inform YNP agencies on the current state of geologic maps in the park and aid in prioritizing resources to achieve a more accurate, higher resolution map to guide infrastructure decisions, scientific studies, and engage the 4+ million visitors that enter Yellowstone each year. These results have implications for future mappers who undertake projects that involve comparing and reassessing map areas that consist of multiple individual maps.