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Recognizing the Albian-Cenomanian (OAE1d) sequence boundary using plant carbon isotopes: Dakota Formation, Western Interior Basin, USA

¹ School of Geography and Earth Sciences, McMaster University, Hamilton, Ontario L8S 4K1, Canada
² Kansas Geological Survey, University of Kansas, Lawrence, Kansas 66047-3726, USA
³ Iowa Department of Natural Resources, Geological Survey, Iowa City, Iowa 52242-1319, USA
⁴ Department of Earth Sciences, University College London, London WC1E 6BT, UK
⁵ Conservation and Survey Division, School of Natural Resources, University of Nebraska–Lincoln, Lincoln, Nebraska 68588-0517, USA
⁶ Department of Geography and Geology, University of Southern Mississippi, Hattiesburg, Mississippi 39406, USA
⁷ Aeon Biostratigraphic Services, 6501 Shale Circle, Anchorage, Alaska 99516, USA

Analysis of bulk sedimentary organic matter and charcoal from an Albian-Cenomanian fluvial-estuarine succession (Dakota Formation) at Rose Creek Pit (RCP), Nebraska, reveals a negative excursion of 3 in late Albian strata. Overlying Cenomanian strata have ¹³C values of –24 to –23 that are similar to pre-excursion values. The absence of an intervening positive excursion (as exists in marine records of the Albian-Cenomanian boundary) likely results from a depositional hiatus. The corresponding positive ¹³C event and proposed depositional hiatus are concordant with a regionally identified sequence boundary in the Dakota Formation (D₂), as well as a major regressive phase throughout the globe at the Albian-Cenomanian boundary. Data from RCP confirm suggestions that some positive carbon-isotope excursions in the geologic record are coincident with regressive sea-level phases. We estimate using isotopic correlation that the D₂ sequence boundary at RCP was on the order of 0.5 m.y. in duration. Therefore, interpretations of isotopic events and associated environmental phenomena, such as oceanic anoxic events, in the shallow-marine and terrestrial record may be influenced by stratigraphic incompleteness. Further investigation of terrestrial ¹³C records may be useful in recognizing and constraining sea-level changes in the geologic record.

Key Words: oceanic anoxic event • carbon isotopes • plants • sequence boundary • Albian-Cenomanian • middle Cretaceous

This article has been cited by other articles:

				P. J. van Hengstum, E. G. Reinhardt, F. S. Medioli, and D. R. Grocke EXCEPTIONALLY PRESERVED LATE ALBIAN (CRETACEOUS) ARCELLACEANS (THECAMOEBIANS) FROM THE DAKOTA FORMATION NEAR LINCOLN, NEBRASKA, USA Journal of Foraminiferal Research, October 1, 2007; 37(4): 300 - 308. [Abstract] [Full Text] [PDF]