Marine connections in North America during the late Maastrichtian: palaeogeographic and palaeobiogeographic significance ofJeletzkytes nebrascensisZone cephalopod fauna from the Elk Butte Member of the Pierre Shale, SE South Dakota and NE Nebraska |
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| Authors: | WJ Kennedy NH Landman WK Christensen WA Cobban JM Hancock |
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| Institution: | aGeological Collections, University Museum, Parks Road, Oxford OX1 3PW, UK;bDepartment of Invertebrates, American Museum of Natural History, Central Park West at 79th St. New York, New York 10024, USA;cGeologisk Museum, University of Copenhagen, Øster Voldgade 5-7, 1350 Copenhagen K, Denmark;d70 Estes Street, Lakewood, Colorado 80226, USA;eImperial College of Science Technology and Medicine, Royal School of Mines, Prince Consort Road, London, SW7 2BP, UK |
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| Abstract: | 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 theFeletzkytes nebrascensisZone, best known from the near-shore facies of the Fox Hills Formation. ThenebrascensisZone 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, ofMicula 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-Cretceous erosion) may have extended well to the north of the shoreline position indicated in recent palaeogeographic reconstructions. |
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| Keywords: | cephalopods biogeography palaeogeography USA Cretaceous Maastrichtian |
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