New Mexico Geological Society Annual Spring Meeting — Abstracts

Late Cretaceous ammonites were collected from the Satan Tongue of the Mancos Shale near La Ventana where the Satan Tongue is ~170 m thick between the El Vado Member of the Mancos Shale (below) and the Point Lookout Sandstone (above). The ammonite fauna includes Clioscaphites vermiformis, Glyptoxoceras novimexicanum, G. sp., Placenticeras syrtale, P. placenta, Desmoscaphites erdmanni, D. bassleri, Scaphites leei I, II, ?III, Baculites codyensis, B. thomi and B. haresi. Thus, the Satan Tongue includes the following ammonite zones locally: Clioscaphites vermiformis Zone (~ lower 10 m), Desmoscaphites erdmanni Zone (~ 60-70 m above base) and Desmoscaphites bassleri Zone (~110-130 m above base) possibly overlain by the zone of Scaphites leei III (upper ~ 20 m). The Clioscaphites vermiformis Zone also occurs in the Satan Tongue in the Ortiz Mountains in Santa Fe County. C. vermiformis, in association with Baculites codyensis and Glyptoxoceras novimexicanum, has also been reported from the upper shale unit of the Smoky Hill Member of the Niobrara Formation in the Raton Basin. The type specimen of G. novimexicanum was collected from the upper part of the Mancos Shale near Waldo in Santa Fe County. Placenticeras syrtale has been reported from the upper part of the Mancos Shale in the upper Rio Grande Valley. Desmoscaphites erdmanni, along with Baculites thomi, has also been reported from the upper shale unit of the Smoky Hill Member of the Niobrara Formation in Colfax County. Desmoscaphites bassleri has been reported to occur in the Mancos Shale east of Shiprock in San Juan County. D. bassleri has also been reported from the upper shale unit of the Smoky Hill Member of the Niobrara Formation in the Raton Basin. Scaphites leei I and II have been reported from the uppermost part of the Mancos Shale in north-central New Mexico. Scaphites leei III has been reported from the Mancos on the eastern side of the San Juan Basin and the Ortiz Mountains. Baculites haresi occurs in the upper part of the Mancos Shale in the San Juan Basin and upper Rio Grande Valley. B. haresi also occurs in the lower Campanian in the Western Interior and Placenticeras placenta also occurs in the lower to upper Campanian in the U.S. The C. vermiformis Zone is middle Santonian and the D. erdmanni and D. bassleri zones are upper Santonian. The S. leei III Zone is lowest lower Campanian.