393 Pliensbachian–Toarcian (Early Jurassic) Ammonoids

In this study, we describe lower Pliensbachian to lower Toarcian ammonoids from 10 stratigraphic sections in the New York Canyon and Westgate areas of the Luning Embayment, Gabbs Valley, and Clan Alpine Mountain Ranges, west-central Nevada, USA. Ammonoid biostratigraphy based on 408 specimens representing 23 genera and 50 species indicates the presence of the Whiteavesi, Freboldi, Kunae, and Carlottense zones of the Pliensbachian and the Kanense Zone of the lower Toarcian. The following five new species are established (in alphabetical order): Nodicoeloceras middlegatense n. sp., Nodicoeloceras nevadaense n. sp., Prodactylioceras westgatenses n. sp., Protogrammoceras (Matteiceras) tipperi n. sp., and Reynesocoeloceras corvalani n. sp.

A volcanic ash bed within the basal New York Canyon type V section yielded a 206-PB / 238-U Chemical Abrasion-Isotope Dilution-Thermal Ionization Mass Spectrometry (CA-ID-TIMS) age of 188.98 +/- 0.11 Ma from the middle-upper part of the Whiteavesi Zone, which will contribute to the refinement of the early Pliensbachian timescale, an interval that is at present poorly constrained.