Upper campanian (upper cretaceous) ammonites from the Marshalltown Formation-Mount laurel boundary beds in Delaware
Journal of Paleontology
By: W. J. Kennedy and W. A. Cobban
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Abstract
New collections from the Marshalltown Formation and basal Mount Laurel Sand along the Chesapeake and Delaware Canal in Delaware clarify the ammonite dating of the interval. The Marshalltown Formation yields Pachydiscus (Pachydiscus) sp., Menuites portlocki (Sharpe, 1855) complexus (Hall and Meek, 1856), a subspecies restricted to the Baculites gregoryensis and Baculites scotti zones in the Western Interior of the United States, and Didymoceras binodosum (Kennedy and Cobban, 1993a) known only from the B. scotti zone of the Western Interior and correlatives in Arkansas and Texas. The basal part of the Mount Laurel Sand contains a complex assemblage preserved as phosphatic molds: Nostoceras (Nostoceras) monotuberculatum Kennedy and Cobban, 1993a, Nostoceras (N.) sp., Didymoceras platycostatum (Kennedy and Cobban, 1993b), D. stevensoni (Whitfield, 1877) (previously thought to be from the Marshalltown) and Exiteloceras jenneyi (Whitfield, 1877). The last two are index species of their eponymous zones in the Western Interior. This sequence is compatible with ammonites from the Wenonah Formation, which lies between the Marshalltown and Mount Laurel to the north and contains ammonites indicative of the Baculites scotti zone, and the fauna from higher in the Mount Laurel Sand, which includes elements of the Didymoceras cheyennense and Baculites compressus zones of the Western Interior sequence.
| Publication type | Article |
|---|---|
| Publication Subtype | Journal Article |
| Title | Upper campanian (upper cretaceous) ammonites from the Marshalltown Formation-Mount laurel boundary beds in Delaware |
| Series title | Journal of Paleontology |
| Volume | 71 |
| Issue | 1 |
| Year Published | 1997 |
| Language | English |
| Larger Work Type | Article |
| Larger Work Subtype | Journal Article |
| Larger Work Title | Journal of Paleontology |
| First page | 62 |
| Last page | 73 |
| Google Analytic Metrics | Metrics page |