New Mexico Geology

Invertebrate trace fossils from the Albian Mesilla Valley Formation (Washita Group) at Cerro de Cristo Rey, Sunland Park, NM represent the following ichnotaxa: Ancorichnus isp., Arenicolites isp., Bergueria isp., Bichordites sp., Cardioichnus foradadensis, C. biloba, Chondrites intricatus, Cochlichnus anguineus, Coprulus oblongus, Gordia marina, Helicodromites isp., Lockeia isp., Ophiomorpha nodosa, Palaeophycus tubularis, P. striatus, P. heberti, Planolites isp., Protovirgularia dichotoma, Rhizocorallium commune var. irregulare (with Coprulus oblongus), Skolithos isp., Sponge­liomorpha isp., S. sublumbricoides, S. oraviense, Taenidium isp., Thalassinoides isp., T. paradoxicus, Treptichnus isp., a chimney structure (Chomatichnus?), and the biofilm Rugalichnus (“Kinneyia”). This is the first study of the invertebrate ichnology of any of the shallow marine units at Cerro de Cristo Rey. The Mesilla Valley Formation contains a medium/high diversity ichnoassemblage, including fugich­nia (i.e., Skolithos), fodichnia (i.e., Chondrites), domichnia (i.e., Ophiomorpha, Thalassinoides), repichnia (Protovirgu­laria), paschichnia (i.e., Palaeophycus), and cubichnia (i.e., Bergaueria, Cardioichnus, Lockeia), as well as compound traces and composite traces. This ichnoassemblage was preserved in tempestites (storm deposits) from below wave base on the upper/middle continental shelf during Oceanic Anoxic Event 1d and contains ichnotaxa representative of the proximal Cruziana ichnofacies (with Skolithos influence).