The Pennsylvanian section at Cedro Peak: A local Pennsylvanian reference section in the Manzanita Mountains, central New Mexico (USA)

Abstract

At Cedro Peak in the Manzanita Mountains of Bernalillo County, New Mexico, a nearly complete, structurally uncomplicated, fossiliferous and characteristic local Pennsylvanian section is exposed. Approximately 340 m thick, we assign this section to the (in ascending order) Sandia, Gray Mesa (= Los Moyos), Atrasado (= Wild Cow), and Bursum Formations. We divide the Gray Mesa Formation into the (in ascending order) Elephant Butte, Whiskey Canyon, and Garcia Members, and we divide the Atrasado Formation into the (in ascending order) Bartolo, Amado, Tinajas, Council Spring, Burrego, Story, Del Cuerto, and Moya Members. We thus reject the names Sol se Mete, Pine Shadow, and La Casa for member-level subdivisions of the Atrasado Formation. We describe the lithostratigraphy, microfacies, and paleontology of the Pennsylvanian strata at Cedro Peak to interpret their depositional environments and age. The approximately 14-m-thick Sandia Formation is almost entirely of nonmarine origin and is assigned an Atokan age based on regional correlations. The approximately 119-m-thick Gray Mesa Formation records normal marine deposition. It contains fusulinids from latest Atokan? to middle Desmoinesian age. The approximately 200-m-thick Atrasado Formation is a complex succession of marine and nonmarine (mostly fluvial-deltaic) strata. It contains fusulinids of Missourian and middle Virgilian age. Only the lowermost 6 m of the Bursum Formation are exposed at Cedro Peak, but nearby sections indicate a Bursum thickness of approximately 90 m and yield Virgilian-age fusulinids. The continuity of the stratigraphic architecture of the Gray Mesa and Atrasado Formations from the Oscura Mountains in Socorro County to Cedro Peak, a distance of approximately 150 km, suggests that Middle–Late Pennsylvanian sedimentation was driven by the same underlying forces over much of central New Mexico. We posit these forces as a series of tectonic events overprinted at a few points by eustatic cycles.