FAUNAL ANALYSIS AND PALEOECOLOGY OF THE CRETACEOUS TEPEE BUTTE LIMESTONES, CENTRAL COLORADO
The life habits and distribution of the fauna help to reconstruct the paleoecology and topographic expression of the seep systems on the sea floor. We measured diversity and abundance across 14 buttes from four separate butte clusters spanning approximately 75 km between Fountain and Boone, CO. In addition to N. occidentalis, other taxa include several species of inoceramid, two species of gastropod, baculites, and at least three species of heteromorphic ammonites including Solenoceras sp. and Didymoceras spp.
The buttes exhibit a general north to south increase in faunal abundance most noted in the ammonoid species. There are a number of factors that may control this trend including nutrient supply, oxygenation, and current direction, as well as the role of taphonomic processes. Faunal trends also differ among six established lithofacies; three display higher faunal diversity and abundance. The distribution and abundance of species helps to reconstruct the paleoecology within the facies. An abundance of articulated clams indicates that they are in place near the sediment-water interface, although not necessarily in life position. The presence of gastropods and inoceramids suggests the availability of substrates upon which to graze and cement. Abundant ammonites, in higher densities than the surrounding shale, may show the presence of a desirable food source in and around the seeps. These observations help to reinterpret the paleoecology and topographic expression of the Tepee Buttes within the Western Interior Seaway.