Great Basin Naturalist


Presumed paludal and alluvial deposits in a small mountain basin in north central Utah have yielded the first terrestrial Pleistocene fauna from the state. Twenty-five mammalian and four nonmammalian species are present, most of which have not previously been reported as fossils from Utah. At 6,400 feet the elevation of this site is much too high to have been part of the Lake Bonneville deposition. Three mammals, Ovis, Symbos, and Bootherium, not existing in the present fauna, have been identified in the northern part of the state. They probably did not reach this area until later in the Pleistocene or else favored more rugged terrain. Previous reports of the Woolly Mammoth, Mammuthus primigenius, from Utah are considered to be in error. M. columbi is probably the represented species. A so-called giant bison, Bison ? latifrons, is represented in the fauna by relatively numerous specimens. The variation in size of these elements strongly suggests that the size range between the largest males and smallest females was much greater than previously assumed.

Most faunal constituents and current topography suggest that the Late Pleistocene habitat at the fossil site was a marsh encircled by a brush-interrupted grassland. The rare remaining faunal components were evidently part of a distant wooded community. A slightly moister but no colder climate than the present one is postulated on the basis of the fauna.

Radiocarbon dating establishes a time for the Silver Creek local fauna in excess of 40,000 YBP. The particular combination of extinct and extant species indicates a Late Sangamon to Early Wisconsin age.