The Upper Boundary of the Eocene Series: A Reappraisal Based on Dinoflagellate Cyst Biostratigraphy and Sequence Stratigraphy
Published:January 01, 1995
Henk Brinkhuis, Henk Visscher, 1995. "The Upper Boundary of the Eocene Series: A Reappraisal Based on Dinoflagellate Cyst Biostratigraphy and Sequence Stratigraphy", Geochronology, Time Scales and Global Stratigraphic Correlation, William A. Berggren, Dennis V. Kent, Marie-Pierre Aubry, Jan Hardenbol
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The IUGS Commission on Stratigraphy recently acccepted and ratified a proposal to establish an Eocene/Oligocene (E/O) boundary stratotype section and point (GSSP) in the pelagic Massignano section (central Italy), characterized by the last occurrence of the Hantkeninidae (planktonic foraminifera). However, detailed dinoflagellate cyst zonation of the E/O transition interval in the Mediterranean area indicates that this newly selected ’golden spike’ horizon correlates to the middle part of the classic (marginal marine) Priabonian type section in northeast Italy. The coeval level occurs well below two earlier proposed E/O boundary stratotypes at Priabona.
In this paper, it is outlined that selection of either one of the proposed boundary-stratotypes at Priabona is more suitable than a hantkeninid-based E/O boundary. These boundary levels can be traced in different lithofacies by recognition of either the TA4.3/4.4 sequence boundary, or the last occurrence of the dinoflagellate cyst Areosphaeridium diktyoplokus. Particularly, a sequence stratigraphic concept of the E/O boundary enables a reasonable correlation of the upper boundary of the Priabonian with the base of the Rupelian (i.e., base Oligocene) as recognized in its type-area in Belgium. The acceptance of the position of the ’golden spike’ at Massignano as the top of the Priabonian Stage thus creates a new Priabonian/Rupelian boundary problem at the very time old uncertainties and controversies on the mutual delimitation of these stages are becoming resolved. Since only stage boundaries should serve to define chronostratigraphic units of higher rank, it is concluded that the IUGS Commission on Stratigraphy should re-evaluate the status of the Massignano section as the E/O boundary GSSP.
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Geochronology, Time Scales and Global Stratigraphic Correlation
Geochronology, Time Scales, and Global Stratigraphic Correlation - The last decade has witnessed significant advances in analytic techniques and methodologic approaches to understanding earth history. This publication is a well-constructed geochronologic framework that allows estimation of rates of geologic processes, correlation of stratigraphies, and placement of discrete events in temporal order. Resulting from a research symposium at the 67th Annual SEPM meeting in New Orleans, Louisiana, April 1993, the 16 papers of this volume represent a broad spectrum of approaches to understanding earth history and the passage of geologic time.