Corals from the Upper Cretaceous of south-central New Mexico
Spencer G. Lucas and Orin J. Anderson
Fossil corals are extremely rare in the Upper Cretaceous deposits of the Western Interior epicontinental seaway, with only three documented reports in the published literature from New Mexico. We add to this record an occurrence of the ahermatypic coral Archohelia dartoni Wells from Mescal Canyon in the northern Caballo Mountains, Sierra County, New Mexico. The coral fossils occur at a single horizon over approximately 0.7 km of strike in the Rio Salado Tongue of the Mancos Shale, 31 m below the base of the Atarque Sandstone Member and thus are of middle Turonian age. The corals display features characteristic of Archohelia dartoni, including circular individual branches with persistent axial corallites and small, circular corallites that branch at right angles from the axial corallite and ascend the branch in spirals. The coral fossils are isolated and broken branches that occur in lenticular masses of sedimentary breccia or conglomerate as much as 100 cm across and as thick as 25 cm. Coral branches are concentrated near the top of each breccia mass and show no preferred orientation. Clearly, these corals are not an in situ thicket but represent reworked and redeposited debris, perhaps reflecting a Turonian storm event or tsunami, and subsequent thicket destruction.
- Lucas, Spencer G.; Anderson, Orin J., 1998, Corals from the Upper Cretaceous of south-central New Mexico, in: Las Cruces Country II, Mack, G. H.; Austin, G. S.; Barker, J. M., New Mexico Geological Society, Guidebook, 49th Field Conference, pp. 205-207.