New Mexico Geological Society Annual Spring Meeting — Abstracts

Throughout the Sacramento Mountains, the Lower Mississippian (Osagian/Kinderhookian) Caballero Formation disconformity overlies the Upper Devonian (Frasnian) Sly Gap Formation. Near the confluence of Alamo and Deadman Canyons (sec. 3, T17S, R10E, Otero County), a 2-m-thick interval of black shale between the Sly Gap and Caballero Formations has usually been assigned to the Upper Devonian Percha Shale. This shale interval contains bone beds that yield diverse assemblages of conodonts and ichthyoliths. Ichthyoliths from the uppermost of these bone beds, which is right at the Devonian-Mississippian unconformity, represent Phoebodus politus, Protracodus cf. P. vetustus, Protracodus ?orientalis, Protracodus sp., Cladoselache spp., Orodus spp., "Multidentodus" spp. and Thrinacodus ferox. The bone bed also includes fossils of Lingula sp., internal molds of ostracods and bivalves and abundant and diverse phosphatic microcoprolites. Most of the ichthyoliths from this bone bed indicate a Late Devonian age and are components of a diverse and cosmopolitan fauna of marine chondrichthyans.