Kahn, Alicia1, Marie-Pierre Aubry1
(1) Rutgers University, Piscataway, NJ
ABSTRACT: Enhanced Stratigraphic Resolution Around the Paleocene/Eocene Boundary: A Biostratigraphic Proxy for the CIE
The earliest Eocene was a time of sudden and anomalous warming in the high latitudes, associated with significant turnovers among marine and terrestrial organisms. The Carbon Isotope Excursion (CIE) is used as a means of stratigraphic correlation upon which the Paleocene/Eocene boundary is correlated worldwide. The CIE has a characteristic structure, with an initial sharp, 2 to 3‰ negative shift, a subsequent interval of relatively constant, very negative values, followed by a progressive increase towards pre-excursion values. We show here that the CIE can be approximated using the Rhomboaster spp.-Discoaster araneus Association (RD). The stratigraphic range of this calcareous nannoplankton association is restricted to the CIE interval and its acme exactly correlates with the interval of most negative 13C values. In addition, acmes of individual components of the assemblages are characteristic of specific intervals of the CIE. The single acme of D. araneus is strictly correlative with the oldest part of the interval with very low 13C values just above the initial 13C shift. We use four biostratigraphic criteria (the range of the RD, its acme, the acme of D. araneus, and the youngest of two acmes of Rhomboaster spp.) to correlate Paleocene/Eocene boundary sections from the Tethys and Atlantic realm, demonstrating thereby how integrated chemobiostratigraphy enhances stratigraphic correlation with a resolution of a few tens of thousands of years.
AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.