GSA Annual Meeting in Phoenix, Arizona, USA - 2019

Paper No. 229-3
Presentation Time: 2:15 PM


KORT, Anne E., Indiana University, Bloomington, IN 47401 and FAMOSO, Nicholas A., U. S. National Park Services, John Day Fossil Beds National Monument, Kimberly, OR 97848

In 1987, a cyclic prospecting schedule was proposed at John Day Fossil Beds National Monument (JODA) to fulfill JODA’s mission of protecting public paleontological resources across the John Day Basin in central and eastern Oregon. This schedule alternated prospecting between the most productive areas of JODA on a four-year cycle, but a survey of field collection data shows that collection has rarely adhered to the schedule. The core issue with the cyclic prospecting schedule has been that the large area outlined for prospecting each year often exceeds staff limitations. This daunting prospecting area comes from an assumption that the erosional surface will “recharge” with fossils after two years of erosion. We tested this assumption by comparing field collection across years from 2008 to 2019 in the Blue Basin area of the Sheep Rock Unit of JODA. We chose Blue Basin because it has been consistently collected in the past decade and consists only of exposures of the productive lower Turtle Cove Member of the John Day Formation. We digitized field collection data in ArcMap 10.5, considering one field number as one data point and did not account for volume or type of material. We buffered each year’s field data by 15 meters to estimate a total prospecting area for each year. We intersected these areas for all combinations of years to look for overlaps where there were hiatuses in collection. For each overlap area, we calculated the difference in the number of fossil sites between the later and earlier year standardized by area. We compared these results across categories of a 1, 2, 3, 4, or >4 year hiatus using an Analysis of Variance (ANOVA). The ANOVA, calculated in R, returned a p-value of 0.284 indicating no significant difference between different hiatus lengths. These results show that prospecting after a 1 year hiatus can be expected to yield about the same number of fossil sites as after longer hiatuses in collection. This suggests that the soft claystones of Blue Basin reach an equilibrium of fossil exposed and fossil buried or destroyed by erosion in a single winter between field seasons. In an ideal world, this might mean returning to the same spot annually to collect every fossil possible. However, with limited JODA staff and resources, these results show that the return interval will not make a difference in number of fossils collected.