Preservation and diagenesis of soft-bodied fossils and the occurrence of phosphate-associated rare earth elements in the Cambrian (Wuliuan) Spence Shale Lagerstätte

The Spence Shale Lagerstätte is a middle Cambrian (Miaolingian Series; Wuliuan Stage) fossil deposit in northern Utah and southern Idaho, USA. At present, it known to preserve 89 species, from at least 10 phyla, of biomineralizing soft-bodied taxa, represents the only major age Laurentia outside Canadian Rockies. In addition taxonomic diversity, exposures represent variety depositional environments along continental shelf, which have been affected by several diagenetic events, making compelling setting improve our understanding taphonomic pathways as they affect broader Burgess Shale-type (BST) preservation. We present analyses 28 specimens six localities using scanning electron microscopy (SEM) integrated energy dispersive X-ray spectrometry (EDS), together with comparisons published data. Taxa are predominantly preserved combination carbonaceous compressions, iron oxide pyrite replacement, but eldoniids genus Eldonia consistently show enrichment rare earth elements (REE). REE, lanthanum cerium, enriched phosphate mineral monazite, occurs inner coil ludwigi. This pattern, seen all sampled Eldonia, differs previous reports REE association BST preservation being limited one tissue type within specific identifiable taxon. tissues can occur during lifetime an individual or fossilization, we both possible outline processes leading fossils Shale.