Geology and Avifauna of the Late Pleistocene and Middle Holocene Blonquist Rockshelter, Summit County, Utah

The Blonquist Rockshelter, Summit County Utah (NE ¼, Sec. 23, T2N, R6E), is a west-facing bedrock alcove formed in the Eocene Wasatch Formation. The shelter is located on the northern flank of the Uinta Mountains, approximately 80 km northeast of Salt Lake City, at an elevation of 1,884 m (6,180 ft). The interior of the shelter is stratified and contains both exogenous (eolian, fine-grained particles and large particles deposited by water) and endogenous (eboulis, and organic layers) sediments. The organic layers appear to be concentrations of organic debris by packrats and raptors. These organic-rich layers have radiocarbon dates of 11.14 ka, 9.67 ka, 7.99 ka, 6.06 ka, and 5.91 ka. All sediments are very fossiliferous and contain a wide variety of snails, amphibians, small reptiles, birds, and mammals. Fossil collection was accomplished through common collecting techniques, such as 1) exposed surface picking, 2) on site screening, and 3) bulk matrix sampling. In this investigation only the avifauna was addressed. Twenty-eight species of birds are known and all are extant, except for the exterminated Ectopistes migratorius (Passenger pigeon). Twenty-three species represented in the sediments occur in northeastern Utah today; five are extralimital (Aegloius funereus, Tympanuchus cupido, T. pallidicinctus, Meleagris gallopavo, and Dendragapus canadaensis). The first three of the extralimital species are new records for Utah. The presence of the Boreal Owl (A. funereus) in a layer dated between 9.67 ka and 7.99 ka suggests the eboulis was deposited during a cool/cold climate at a time immediately following the recession of local mountain glaciers