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Integrated stratigraphic and astrochronologic calibration of the Eocene-Oligocene transition in the Monte Cagnero section (northeastern Apennines, Italy): A potential parastratotype for the Massignano global stratotype section and point (GSSP)

By
Ethan Hyland
Ethan Hyland
Department of Geology, Carleton College, Northfield, Minnesota 55057, USA, and Osservatorio Geologico di Coldigioco, 62020 Frontale di Apiro, Italy
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Brandon Murphy
Brandon Murphy
Stable Isotope Laboratory, University of California, Santa Cruz, California 95064, USA
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Phil Varela
Phil Varela
Department of Geology, Carleton College, Northfield, Minnesota 55057, USA, and Osservatorio Geologico di Coldigioco, 62020 Frontale di Apiro, Italy
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Katie Marks
Katie Marks
Department of Geology, Carleton College, Northfield, Minnesota 55057, USA, and Osservatorio Geologico di Coldigioco, 62020 Frontale di Apiro, Italy
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Lauren Colwell
Lauren Colwell
Department of Geology, Carleton College, Northfield, Minnesota 55057, USA, and Osservatorio Geologico di Coldigioco, 62020 Frontale di Apiro, Italy
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Flavia Tori
Flavia Tori
Dipartimento di Scienze della Terra dell’Università degli Studi di Firenze, Via La Pira 4, 50121 Firenze, Italy
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Simonetta Monechi
Simonetta Monechi
Dipartimento di Scienze della Terra dell’Università degli Studi di Firenze, Via La Pira 4, 50121 Firenze, Italy
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Laura Cleaveland
Laura Cleaveland
Department of Geological Sciences, Brown University, Providence, Rhode Island 02912, USA
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Henk Brinkhuis
Henk Brinkhuis
Laboratory of Palaeobotany and Palynology, Utrecht University, Budapestaan 4, 3584 CD, Utrecht, The Netherlands
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Caroline A van Mourik
Caroline A van Mourik
Department of Geology and Geochemistry, Stockholm University, S-106 91 Stockholm 9, Sweden
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Rodolfo Coccioni
Rodolfo Coccioni
Istituto di Geologia e Centro di Geobiologia, Università degli Studi di Urbino, 61029 Urbino, Italy
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David Bice
David Bice
Department of Geosciences, Pennsylvania State University, University Park, Pennsylvania 16802, USA, and Osservatorio Geologico di Coldigioco, 62020 Frontale di Apiro, Italy
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Alessandro Montanari
Alessandro Montanari
Osservatorio Geologico di Coldigioco, 62020 Frontale di Apiro, Italy
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Published:
April 01, 2009

We present the results of integrated biostratigraphic (planktonic foraminifera, calcareous nannofossils, and dinoflagellates), magnetostratigraphic, and cyclostratigraphic analyses of the lower part of Monte Cagnero section (Umbria-Marche Apennines of Italy), a continuous and complete succession of pelagic limestone and marls that provides the means for an accurate and precise astrochronologic calibration of the Eocene-Oligocene transition. This 38.5-m-thick section overlaps the Oligocene section, which, at meter level 188, contains the Rupelian-Chattian boundary corresponding to the O4-O5 planktonic foraminiferal zonal boundary within the upper half of magnetochron C10n. The Eocene-Oligocene boundary at Monte Cagnero, as defined by the last occurrence of hantkeninid planktonic foraminifers (E14-E15 zonal boundary), is found at meter level 114.1, in the upper part of calcareous nannofossil zone CP16a, and very near the Aal-Gse dinocyst zonal boundary. Paleomagnetic analysis has identified all the magnetic reversals from the lower C13r to the lower C12n, precisely overlapping the base of the Oligocene magnetostratigraphic succession and placing the Eocene-Oligocene boundary in the upper part of C13r, in full agreement with the global stratotype section and point (GSSP) at Massignano.

Spectral analysis of calcium carbonate data from bulk samples, collected at 5 cm intervals, indicates that orbital forcing of depositional cycles (i.e., limestone versus marl alternations) is dominant at frequencies corresponding to the theoretical astronomical curves of eccentricity, obliquity, and precessional cycles throughout the studied Eocene-Oligocene transition. Correlation with the astrochronologic time scale allows an age assignment of 33.95 Ma for the Eocene-Oligocene boundary, which is in close agreement with the astrochronologic age for the boundary in the GSSP of Massignano obtained in a similar study by R.E. Brown and colleagues in this volume. Thus, the Monte Cagnero section represents a candidate parastratotype for the Eocene-Oligocene GSSP of Massignano in the eventuality that the oxygen and carbon stable isotope shifts defining the oxygen isotope Oi-1 glaciation will be preferred over the last occurrence of hantkeninids as marker for the boundary, since, at Massignano, the beginning of this isotope shift is barely represented in the uppermost part of the exposed section. The excellent integrated stratigraphic framework of Monte Cagnero presented here will significantly facilitate further high-resolution isotope and paleoecological studies across the time of transition from a hothouse to icehouse Earth.

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Contents

GSA Special Papers

The Late Eocene Earth—Hothouse, Icehouse, and Impacts

Christian Koeberl
Christian Koeberl
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Alessandro Montanari
Alessandro Montanari
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Geological Society of America
Volume
452
ISBN print:
9780813724522
Publication date:
April 01, 2009

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