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Upper campanian (upper cretaceous) ammonites from the Marshalltown Formation-Mount laurel boundary beds in Delaware

Journal of Paleontology

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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.

Additional Publication Details

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
Number of Pages:
12