DISARTICULATED COPROLITE MICRO-FACIES FROM THE THERMOPOLIS SHALE, HOT SPRINGS COUNTY, WY

A unique micro-facies consisting of massed vertebrate material in a dense black concreted matrix may represent a disarticulated coprolite layer. The fossil material occurs in a lens type concretion and is represented by teeth and vertebra with a size range of .5mm or less and occurs 42m below the Neogastropiltes haasi ammonite biozone. Though the oyster Inoceramus is ubiquitous throughout the formation, no shell material was noted within the tooth dominated matrix. The most prevalent lens tapers out rapidly into a black fissle shale with bentonite streamers.

A large percentage of the teeth are incomplete, missing accessory cusps or having partial roots suggesting rough deposition. Likewise, pitting on the surface of some teeth suggests gastric damage; however, some material could have been damaged by burrowing or bioturbation after deposition. Though complete fish jaws with teeth were found in fine-grained silt-stone concretions within the same facies, the bone material in the dark iron-stone matrix was broken at rough edges with no teeth articulated to any jaw portion.

Though a lag deposit, the fragmented material does not suggest collection through natural winnowing through the matrix as there is no defined layering, nor orientation. Likewise, an isolated mass of teeth all within the same range of size and shape displays an orange-yellow grain staining. The presence of this mass in contact with other unstained material may suggest an incomplete breakdown of the coprolite source material.