THE SNOWMASTODON SITE: INVESTIGATION OF THE YELLOW-BANDED SILT

In October 2010, bones of a juvenile Columbian mammoth were found during excavation of a small reservoir near the town of Snowmass Village, Colorado. Subsequent excavation efforts led by the Denver Museum of Nature and Science have recovered more than 4800 bones from at least 26 different Pleistocene taxa, including mammoths, mastodons, ground sloths, bison, camel, and horse, as well as smaller mammals, reptiles, and birds. At this site, informally called the “Snowmastodon Site”, a yellow-banded silt unit is present that delineates the approximate transition between mastodons (below) and mammoths (above). The unique yellow color likely represents chemical and mineralogical differences between this and adjacent units, which may be related to changes in depositional environments. During the summer of 2011, we collected multiple samples from the yellow-banded silt and adjacent units in order to physically and chemically characterize the sediments and ascertain information related to their depositional context. X-Ray diffraction analysis was performed to examine the mineralogical composition of the samples, energy-dispersive x-ray fluorescence was done to quantify elemental concentrations, and particle-size analysis was conducted in order to characterize grain sizes of the samples. Results of these analyses did not reveal significant differences between the yellow-banded silt and adjacent units. However, the yellowish color of the banded silt suggests that the iron (and possibly manganese) species are oxidized, which implies that its deposition occurred during a period of especially shallow water depths. Faunal remains, including abundant tiger salamanders, snakes, and rodents, also suggest water depths were especially shallow at this time. Work is ongoing to constrain the ages, identify possible sediment sources, and further improve our understanding of depositional environments of the yellow-banded silt and other units present at this site.