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Taphonomy of the Lower Permian Geraldine Bonebed in Archer County, Texas

1987; Elsevier BV; Volume: 61; Linguagem: Inglês

10.1016/0031-0182(87)90051-4

1872-616X

P. Martin Sander,

Ecology and Vegetation Dynamics Studies

Lower Permian Admiral Formation redbeds in north Texas are famous for their vertebrate fauna. This paper provides a detailed taphonomic analysis of the Geraldine Bonebed in central Archer County, Texas, one of the most important fossil vertebrate occurrences in the region. The Geraldine Bonebed is situated in the floodbasin facies (red and gray mudstones with abundant Psaronius roots) of a small meandering river system. Such basins were covered with a dense swamp forest with a high diversity of vertebrates. The Geraldine Bonebed has yielded, from an area of 30 m2, 44 partly articulated skeletons of four genera of tetrapods and the remains of another eight vertebrate taxa. The bones lie on a layer of fern, and conifer foliage and wood intermingled with fossil charcoal. The sediment, the occurrence of "Wasserleichen", and the skeleton orientation indicate post-mortem transportation and deposition in water. A single mass death event, which could have been a forest fire, drove the animals into a pond where they perished. Carcasses floating in water together with plant debris were concentrated by wind-induced drift into this exceptional fossil deposit. A recent example of this process of bonebed formation after mass death was described by Weigelt (1927) from the Texas Gulf Coast.