The first record of Cancelloceras (Early Pennsylvanian Ammonoidea) from southern Nevada: Implications for timing of regional mid-Carboniferous sea-level fluctuations

Abstract

In 1988, the presence of an Early Pennsylvanian ammonoid assemblage within the basal meter of the Callville Formation (Pennsylvanian-Permian), eastern Clark County, Nevada, was brought to the attention of the author by Stephen M. Rowland, University of Nevada-Las Vegas. The ammonoids occur in the Frenchman Mountain section described by Rowland (1987) for the Geological Society of America's Decade of North American Geology (DNAG) field trip compendium. The mid-Carboniferous section at this locality (Figure 1) was discussed in two other field trip guides as well (Langenheim and Webster, 1979; Webster et al., 1984). No ammonoids have been reported previously from this locality. Although this is the first record of Cancelloceras from the Great Basin region, the assemblage also provides a narrowly constrained age for the basal part of the Callville Formation at Frenchman Mountain, which in turn, dates the initiation of carbonate deposition following a major mid-Carboniferous hiatus in the southern Great Basin.