GSA Connects 2021 in Portland, Oregon

Paper No. 75-10
Presentation Time: 10:50 AM


BENOY, Russell, Pomona College, Geology, 185 E 6TH ST, CLAREMONT, CA 91711-4421 and MCLAUGHLIN, Win, Geology, Pomona College, 185 E. Sixth Street, Claremont, CA 91711

New work on Late Miocene localities establishes insight into the evolving Basin and Range ecosystems in North Eastern Nevada, an area which has received little to no attention in the past. Preliminary work north of Wells, Nevada led to the discovery of vertebrate material which has been measured, identified, and analyzed for their weathering stage and other signs of paleoecology, to drive this taphonomic study. An initial 292 fossil fragments have been analyzed so far. While this is a fraction of the total material collected, it does give some early insight towards the expected taphonomic setting of the fossils. Categorizing each fragment’s weathering stage in correlation to inferred time on surface prior to burial shows most elements to have moderate to extreme surface weathering, implying 1-3 years or greater from death to burial. This corresponds to a lack of articulated fossils at any sites. Using the maximum length measurements of these fossils infers the total transport distance as having been quite extensive. While these fragments are largely unidentifiable, the large quantity of fragments still offers many with traceable taxonomy. The mechanism for burial, found through our sections, is reworked ash, meaning that it didn’t directly fall onto this landscape but was washed into the basins from areas of higher topography; this suggests both that the Basin and Range structure was already in place and that this is an attritional community of organisms. From the fossils which we can identify, we see predominantly herbivores and large ungulates. However, there is evidence of microvertebrates and carnivores, including an exceptional mustelid jaw deserving of further study. In addition, bone processing marks consistent with larger carnivores were prevalent. While preliminary, this diverse assemblage shows no preservation biases. With the dynamic change in the intermontane American West as the Basin and Range evolves, the ecological communities are changing too. By assessing the taphonomy of the fossils within the rock record, we begin to see the bigger picture of what this landscape really looked like during a turbulent time. Comparing this work to the more well documented and studied areas of Eastern Oregon and Southern California can better help to assess the impact of Basin and Range of taxonomic ranges.