BRINGING OUT THE DEAD: UNTANGLING SOFT-BODIED PRESERVATION IN THE CAMBRIAN SPENCE SHALE OF UTAH AND IDAHO

The middle Cambrian (Miaolingian Series, Wuliuan Stage) Spence Shale Member of the Langston Formation in northeastern Utah and southeastern Idaho is a relatively well-known Burgess Shale-type deposit. In addition to its abundant biomineralized fauna, the soft-bodied biota preserved in the Spence is diverse, including various arthropods, priapulids, deuterostomes, and lobopodians. While the Spence Shale is often regarded as a single deposit in the literature, it is imperative to recognize that there are notable differences between the separate outcrops. Not only are there variations in sedimentology, modes of preservation of the soft-bodied fossils, and fossil diversity at the outcrop scale, but these elements can also vary within a few meters of the same exposure. Part of this variation is attributed to changing depositional environments along the continental shelf, but modern weathering and historical collections bias may also play significant roles. However, understanding the correlative nature of these proxies is in its infancy. Here we present new data from sedimentological, petrographic, paleontological, geochemical, and SEM-EDS analyses which showcase the importance of a multiproxy approach to the understanding of this convoluted deposit. Our aim is to provide improved clarity onto the paleoecological and taphonomic questions that have plagued the Spence Shale for decades.