New Mexico Geological Society Annual Spring Meeting & Ft. Stanton Cave Conference — Abstracts

Current fieldwork in the lowermost Albian-Cenomanian Mojado Formation (Sarten member) has produced several new invertebrate trace fossil discoveries. Reported here is the third documented occurrence of Planolites isp. in the Washita Group at Cerro de Cristo Rey Sunland Park, New Mexico, and the first record of this trace in the Mojado Formation. Planolites is a simple, sub-horizontal, cylindrical trace with fill that is different than the host rock. It is interpreted as a domichnia (dwelling trace) or fodichnia (feeding trace) with several possible tracemakers. It is preserved in most environmental settings including marine and continental, from the Ediacaran to Recent. At this locality this trace is associated with Arthrophycus, Thalassinoides, and Curvolithus, so we tentatively assign this ichnoassemblage to the Cruziana ichnofacies. Although ichnoassemblages attributed to the Cruziana ichnofacies have been described a few meters below in the Mesilla Valley Formation, these differ from the low-diversity ichnoassemblage in the Mojado Formation. This change in ichnoassemblage may in the future be used to define the lower contact of the Mojado Formationat Cristo Rey.

Keywords: invertebrate ichnology, trace fossils, Cerro de Cristo Rey, Mojado formation, Planolites, Cruziana ichnofacies

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