--> Abstract: Towards A Revised Cenozoic Geochronology, by W. A. Berggren, M-P. Aubry, and D. V. Kent; #90987 (1993).

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BERGGREN, WILLIAM A., Woods Hole Oceanographic Institution, Woods Hole, MA; MARIE-PIERRE Aubry, Laboratoire de Geologie du Quaternaire, CNRS-Luminy, Marseille, France; and DENNIS V. KENT, Lamont-Doherty Geological Observatory, Palisades, NY

ABSTRACT: Towards A Revised Cenozoic Geochronology

A recently revised Late Cretaceous-Cenozoic magnetochronology has served as the template upon which a revised calcareous and siliceous magnetobiochronology is being constructed. We present a brief review of the basic construction of, and some recently revised first order correlations to, this new global polarity time scale (GPTS). In addition we discuss: 1)problems associated with the magneto-vs astronomical chronologies between 3.5 and 5+Ma; 2) paleomagnetic calibration of revised and (re)defined Neogene planktonic foraminiferal biostratigraphy and implications for revised age/stage boundary estimates; 3) arevised Neogene global marine-terrestrial stratigraphic correlation network; 4) the implications of this new time scale for age estimates of several major

epoch/series boundaries of theCenozoic: Pliocene/Pleistocene (C2n; 1.76Ma [1.81Ma in Astronomical Time Scale]); Miocene/Pliocene (C3n.4r; 5.2Ma [5.32Ma in ASTS]); Oligocene/Miocene (C6C.2n; 23.8Ma);Eocene/Oligocene (C13r; 33.7Ma); Paleocene/Eocene (C24.3r; 55Ma); Cretaceous/Paleocene (C29r; 66 Ma) based on recent studies conducted under the aegis of IGCP and IUGS (Subcommision on Neogene Stratigraphy) activities; 5) application of the revised chronology to a sequence stratigraphic analysis of Paleocene/Eocene boundary sections of NW Europe. Boundary "definitions" by marine and terrestrial stratigraphers are situated at different levels in the integrated magneto/bio/chemostratigraphic record: as presently defined the P/E boundary lies at the base of the London Clay Formation, near the- 7 ash level, within the Deflandrea oebisfeidensis Acme Zone, and equivalent to a level within lower NP10 and probably at or near the P6a/b boundary, in C24.3r with an age estimate of 55Ma; the NP9/10 boundary of calcarous nannoplankton biostratigraphers lies in the lower part of C24.3r with an age estimate of 55.3Ma; the Conglomerate de Meudon at the base of the Argile Plastique (base Spamacian of vertebrate paleontologists) is associated with an unconformity corresponding to a minor sequence boundary (with a brief hiatus=HP4 in the Paris Basin) separating it from the underlying Sables de Bracheux (mid-NP9) and has an estimated age of 55.7 Ma. The major (apparently coupled) atmospheric-climatic-deep sea circulation and benthic faunal extinction events appear synchronous in the stratigrap ic record and to correspond to a level in early C24.3r at or near the NP9/10 boundary and within Biochron P6a.

AAPG Search and Discovery Article #90987©1993 AAPG Annual Convention, New Orleans, Louisiana, April 25-28, 1993.