DIATREMES ARE A GULL'S BEST FRIEND: GEOLOGY AND AVIAN TAPHONOMY OF FOSSIL LAKE, OREGON

The South Dakota School of Mines and Technology Museum of Geology has amassed a new and extensive collection from the at Fossil Lake, Oregon. In this new collection, virtually all specimens are tied to a set of lithologically distinct units. The current study has resulted in the reinterpretation of the environment of deposition for the historic and scientifically significant vertebrate fossil locality at Fossil Lake, Oregon, and a diatreme-maar is suggested as the primary mechanism that controlled and influenced accumulation and preservation of the fossils at Fossil Lake.

The large number of specimens and the degree of stratigraphic and spatial control imposed by the SDSM&T collecting methodology provide an unparalleled opportunity for new studies of the locality. Class-level taxonomy and gross taphonomic condition were tabulated for a sample of 9365 specimens collected over six field seasons. Five hundred sixty isolated fossil bird bones and one skeleton collected during 1990 were identified and examined for taphonomic condition. Four fossils and four sediment samples were analyzed by SEM-based methods. Patterns of accumulation, preservation, breakage, and weathering within the deposit are incorporated into a taphonomic and paleoenvironmental model.