Recognizing the Albian-Cenomanian (Oae1d) Sequence Boundary Using Plant Carbon Isotopes: Dakota Formation, Western Interior Basin, USA
Recognizing the Albian-Cenomanian (OAE1d) sequence boundary using plant carbon isotopes: Dakota Formation, Western Interior Basin, USA Darren R. GroÈcke School of Geography and Earth Sciences, McMaster University, Hamilton, Ontario L8S 4K1, Canada Gregory A. Ludvigson Kansas Geological Survey, University of Kansas, Lawrence, Kansas 66047-3726, USA Brian L. Witzke Iowa Department of Natural Resources, Geological Survey, Iowa City, Iowa 52242-1319, USA Stuart A. Robinson Department of Earth Sciences, University College London, London WC1E 6BT, UK R.M. Joeckel Conservation and Survey Division, School of Natural Resources, University of Nebraska±Lincoln, Lincoln, Nebraska 68588-0517, USA David F. Ufnar Department of Geography and Geology, University of Southern Mississippi, Hattiesburg, Mississippi 39406, USA Robert L. Ravn Aeon Biostratigraphic Services, 6501 Shale Circle, Anchorage, Alaska 99516, USA ABSTRACT To ascertain the effect of OAE1d (latest Albian) on the terrestrial Analysis of bulk sedimentary organic matter and charcoal carbon-isotope record, we collected bulk sediment and plant macro- from an Albian-Cenomanian ¯uvial-estuarine succession (Dakota fossils for organic carbon-isotope analysis from the Rose Creek Pit Formation) at Rose Creek Pit (RCP), Nebraska, reveals a negative (RCP) in the Dakota Formation, near Fairbury, Nebraska (Fig. 1). Pa- excursion of ;3½ in late Albian strata. Overlying Cenomanian lynostratigraphy places the section at RCP as late Albian to Cenoman- strata have d13C values of 224½ to 223½ that are similar to pre- ian in age (Brenner et al., 2000). A direct comparison between our d13 d13 excursion values. The absence of an intervening positive excursion terrestrial C records from RCP and the oceanic Cforam record at (as exists in marine records of the Albian-Cenomanian boundary) ODP Site 1052 (Wilson and Norris, 2001) provides better time reso- likely results from a depositional hiatus.
[Show full text]