Marine connections in North America during the late Maastrichtian: Palaeogeographic and palaeobiogeographic significance of Jeletzkytes nebrascensis Zone cephalopod fauna from the Elk Butte Member of the Pierre Shale, SE South Dakota and NE Nebraska

• Published in: Cretaceous Research
• Main Authors: Kennedy, W, Landman, N, Christensen, W, Cobban, W, Hancock, J
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2016
• Subjects: Greenland; North Atlantic
• Online Access: https://doi.org/10.1006/cres.1998.0129; https://ora.ox.ac.uk/objects/uuid:045c7170-139e-435b-b31c-f939c99b9233

The Elk Butte Member of the Pierre Shale of southeast South Dakota and northeast Nebraska yields a late Maastrichtian cephalopod fauna of nautiloids, belemnites and ammonites of the Jeletzkytes nebrascensis Zone, best known from the near-shore facies of the Fox Hills Formation. The nebrascensis Zone is the highest distinct marine assemblage that can be recognised in the Western Interior, although ammonites occur as rarities high in the Lance Formation in Wyoming. Elements of the fauna occur in the Gulf Coast and Atlantic Seaboard, and extend into the highest Maastrichtian nannofossil Subzone CC26b, of Micula prinsii, in Texas. These occurrences point to the existence of a southerly marine route for migration into and out of the northern Interior during the late late Maastrichtian. An analysis of Maastrichtian ammonite occurrences in West Greenland reveals no evidence for a marine link to the Western Interior at this time, but rather indicates an open marine link to the North Atlantic region. The presence of upper upper Maastrichtian Pierre Shale in southeast South Dakota and northeast Nebraska, deposited in water depths that are conservatively estimated at 100-200 m, suggests that marine conditions (evidence for which has been removed by post-Cretaceous erosion) may have extended well to the north of the shoreline position indicated in recent palaeogeographic reconstructions.