IMPACT OF EMERGENT TOPOGRAPHY ON FAUNAL COMMUNITIES IN THE BASIN AND RANGE

Today the Basin and Range geomorphic province spans the whole state of Nevada, reaching the edges of neighboring states. This region contains several ecosystems found nowhere else on earth, including mountainous, forested cloud islands and desert playa valleys. Pleistocene pluvial systems, add regional geomorphic heterogeneity that contributes to this ecological diversity. We conducted a preliminary study on when these novel ecosystems developed, to better understand when and how the region tectonic geomorphology became a barrier dividing these ecosystems, focusing on the development of distinctive modern microclimates. We are investigating a new set of fossiliferous localities north of Wells Nevada, in the northern-most edge of the Basin and Range. Previously the deposits were mapped on a state level as Barstovian North American Land Mammal Age. Earlier paleontologists describe occurrences of scattered, scrappy vertebrate fossils during the 1950s. The limited amount and low quality of these fossils material discouraged more detailed paleontological surveys. After revisiting the site in 2017 and we found more promising material including a nearly complete Teleoceras rhino jaw. Our fossil evidence suggests it is younger than previously thought, namely late Miocene to Pliocene in age. While still fragmentary, the fossil megafauna shares similarities with Great Plains communities than either Oregon or Californian faunas of the same ages, while the microvertebrates are most similar to more proximal intermontane west communities. I believe this reflects rapid development of the Basin and Range topography and the emergence of the high degree of ecological heterogeneity seen today. Large ungulates, such as the rhino, gomphothere, two horses, two camelids, and a palaeomerycid were able to traverse more complex terrain and were less impacted by the emergence of variable elevation terrain, whereas the small vertebrates, such as gophers, packrats, lizards, squirrels, and small mustelids were severely limited by the emergent topographic barriers. Preliminary geochemistry on soil carbonates suggests temperatures as warm as today, with greater precipitation, allowing diverse floral communities capable of supporting large herbivores. This suggests global, rather than local topography, drive the climate.