The Eocene-Oligocene Transition in the South-Western Neo-Tethys (Tunisia): Astronomical Calibration and Paleoenvironmental Changes

Jihede Haj Messaoud; Nicolas Thibault; Chokri Yaich; Johannes Monkenbusch; Hamdi Omar; Hela Fakhfakh Ben Jemai; David K. Watkins

doi:10.1029/2020PA003887

The Eocene-Oligocene Transition in the South-Western Neo-Tethys (Tunisia): Astronomical Calibration and Paleoenvironmental Changes

Jihede Haj Messaoud^*, Nicolas Thibault, Chokri Yaich, Johannes Monkenbusch, Hamdi Omar, Hela Fakhfakh Ben Jemai, David K. Watkins

^*Corresponding author for this work

Research output: Contribution to journal › Article › peer-review

7 Scopus citations

Abstract

A detailed biostratigraphic, chemostratigraphic, and chronostratigraphic study was carried out in the South-Western margin of the Neo-Tethys ocean (Tunisia) covering the Eocene-Oligocene interval to report potential paleoenvironmental and paleoclimatic changes associated with the growth of the Antarctic ice sheet (AIS). The studied section consists of marls and limestones extending from the Helicosphaera compacta nannofossil Zone (CNE21) to the Reticulofenestra umbilicus Zone (CNO2). The Bc of Clausicoccus subdistichus coincides in northeastern Tunisia with the extinction of hantkeninids and is thus used here to define the Eocene/Oligocene boundary (EOB) at 34.03 Ma. Calcareous nannofossil assemblages suggest a significant change from oligotrophic/warm surface waters during the late Eocene to eutrophic/cool waters during the early Oligocene. The observed changes in trophic conditions are synchronous with a shallowing trend testified by an increase in nearshore species and enhanced terrigenous input. Major environmental changes occurred at the EOB and across glaciation event Oi-1a whereas we record a poor imprint of glaciation event Oi-1. Three orbital configurations have been distinguished: (1) The late Eocene is characterized by a prominent 405-kyr cycle and a weak obliquity component; (2) the onset of cooling at 34.35 Ma coincides with the rosette-shaped discoaster extinction and is reflected by a shift toward enhanced obliquity and short-eccentricity cycles. The installation of a fully developed AIS (event Oi-1a, 32.75 Ma) shows the most pronounced obliquity imprint reflecting an increased influence of high-latitude climate processes; (3) after 31.75 Ma, the obliquity decreases in coincidence with the return to a dominant long-eccentricity cycle.

Original language	English (US)
Article number	e2020PA003887
Journal	Paleoceanography and Paleoclimatology
Volume	35
Issue number	8
DOIs	https://doi.org/10.1029/2020PA003887
State	Published - Aug 1 2020

Bibliographical note

Funding Information:
We are grateful for the Department of Geoscience and Natural Resources Management, Copenhagen University, for financing the isotope and XRF analyses. We thank the UNESCO International Geoscience Program (IGCP 652) for their cyclostratigraphic courses and training. J. M. and N. T. were financed through Carlsberg Foundation Project CF16‐0457. Warmly thanks to Haithem Briki and Bilel Souidi for guidance and help in the field. The anonymous reviewers are kindly acknowledged for their thoughtful comments that helped to improve the manuscript significantly. We also thank the Editor Stephen Barker for the time he dedicated in processing our manuscript.

Funding Information:
We are grateful for the Department of Geoscience and Natural Resources Management, Copenhagen University, for financing the isotope and XRF analyses. We thank the UNESCO International Geoscience Program (IGCP 652) for their cyclostratigraphic courses and training. J. M. and N. T. were financed through Carlsberg Foundation Project CF16-0457. Warmly thanks to Haithem Briki and Bilel Souidi for guidance and help in the field. The anonymous reviewers are kindly acknowledged for their thoughtful comments that helped to improve the manuscript significantly. We also thank the Editor Stephen Barker for the time he dedicated in processing our manuscript.

Publisher Copyright:
©2020. American Geophysical Union. All Rights Reserved.

Keywords

calcareous nannofossils
greenhouse-icehouse transition
orbital forcing (eccentricity, obliquity)
paleoclimate modeling
X-ray fluorescence

ASJC Scopus subject areas

Oceanography
Atmospheric Science
Palaeontology

Access to Document

10.1029/2020PA003887

Cite this

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title = "The Eocene-Oligocene Transition in the South-Western Neo-Tethys (Tunisia): Astronomical Calibration and Paleoenvironmental Changes",

abstract = "A detailed biostratigraphic, chemostratigraphic, and chronostratigraphic study was carried out in the South-Western margin of the Neo-Tethys ocean (Tunisia) covering the Eocene-Oligocene interval to report potential paleoenvironmental and paleoclimatic changes associated with the growth of the Antarctic ice sheet (AIS). The studied section consists of marls and limestones extending from the Helicosphaera compacta nannofossil Zone (CNE21) to the Reticulofenestra umbilicus Zone (CNO2). The Bc of Clausicoccus subdistichus coincides in northeastern Tunisia with the extinction of hantkeninids and is thus used here to define the Eocene/Oligocene boundary (EOB) at 34.03 Ma. Calcareous nannofossil assemblages suggest a significant change from oligotrophic/warm surface waters during the late Eocene to eutrophic/cool waters during the early Oligocene. The observed changes in trophic conditions are synchronous with a shallowing trend testified by an increase in nearshore species and enhanced terrigenous input. Major environmental changes occurred at the EOB and across glaciation event Oi-1a whereas we record a poor imprint of glaciation event Oi-1. Three orbital configurations have been distinguished: (1) The late Eocene is characterized by a prominent 405-kyr cycle and a weak obliquity component; (2) the onset of cooling at 34.35 Ma coincides with the rosette-shaped discoaster extinction and is reflected by a shift toward enhanced obliquity and short-eccentricity cycles. The installation of a fully developed AIS (event Oi-1a, 32.75 Ma) shows the most pronounced obliquity imprint reflecting an increased influence of high-latitude climate processes; (3) after 31.75 Ma, the obliquity decreases in coincidence with the return to a dominant long-eccentricity cycle.",

keywords = "calcareous nannofossils, greenhouse-icehouse transition, orbital forcing (eccentricity, obliquity), paleoclimate modeling, X-ray fluorescence",

author = "Messaoud, {Jihede Haj} and Nicolas Thibault and Chokri Yaich and Johannes Monkenbusch and Hamdi Omar and Jemai, {Hela Fakhfakh Ben} and Watkins, {David K.}",

note = "Funding Information: We are grateful for the Department of Geoscience and Natural Resources Management, Copenhagen University, for financing the isotope and XRF analyses. We thank the UNESCO International Geoscience Program (IGCP 652) for their cyclostratigraphic courses and training. J. M. and N. T. were financed through Carlsberg Foundation Project CF16‐0457. Warmly thanks to Haithem Briki and Bilel Souidi for guidance and help in the field. The anonymous reviewers are kindly acknowledged for their thoughtful comments that helped to improve the manuscript significantly. We also thank the Editor Stephen Barker for the time he dedicated in processing our manuscript. Funding Information: We are grateful for the Department of Geoscience and Natural Resources Management, Copenhagen University, for financing the isotope and XRF analyses. We thank the UNESCO International Geoscience Program (IGCP 652) for their cyclostratigraphic courses and training. J. M. and N. T. were financed through Carlsberg Foundation Project CF16-0457. Warmly thanks to Haithem Briki and Bilel Souidi for guidance and help in the field. The anonymous reviewers are kindly acknowledged for their thoughtful comments that helped to improve the manuscript significantly. We also thank the Editor Stephen Barker for the time he dedicated in processing our manuscript. Publisher Copyright: {\textcopyright}2020. American Geophysical Union. All Rights Reserved.",

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AU - Yaich, Chokri

AU - Monkenbusch, Johannes

AU - Omar, Hamdi

AU - Jemai, Hela Fakhfakh Ben

AU - Watkins, David K.

N1 - Funding Information: We are grateful for the Department of Geoscience and Natural Resources Management, Copenhagen University, for financing the isotope and XRF analyses. We thank the UNESCO International Geoscience Program (IGCP 652) for their cyclostratigraphic courses and training. J. M. and N. T. were financed through Carlsberg Foundation Project CF16‐0457. Warmly thanks to Haithem Briki and Bilel Souidi for guidance and help in the field. The anonymous reviewers are kindly acknowledged for their thoughtful comments that helped to improve the manuscript significantly. We also thank the Editor Stephen Barker for the time he dedicated in processing our manuscript. Funding Information: We are grateful for the Department of Geoscience and Natural Resources Management, Copenhagen University, for financing the isotope and XRF analyses. We thank the UNESCO International Geoscience Program (IGCP 652) for their cyclostratigraphic courses and training. J. M. and N. T. were financed through Carlsberg Foundation Project CF16-0457. Warmly thanks to Haithem Briki and Bilel Souidi for guidance and help in the field. The anonymous reviewers are kindly acknowledged for their thoughtful comments that helped to improve the manuscript significantly. We also thank the Editor Stephen Barker for the time he dedicated in processing our manuscript. Publisher Copyright: ©2020. American Geophysical Union. All Rights Reserved.

PY - 2020/8/1

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N2 - A detailed biostratigraphic, chemostratigraphic, and chronostratigraphic study was carried out in the South-Western margin of the Neo-Tethys ocean (Tunisia) covering the Eocene-Oligocene interval to report potential paleoenvironmental and paleoclimatic changes associated with the growth of the Antarctic ice sheet (AIS). The studied section consists of marls and limestones extending from the Helicosphaera compacta nannofossil Zone (CNE21) to the Reticulofenestra umbilicus Zone (CNO2). The Bc of Clausicoccus subdistichus coincides in northeastern Tunisia with the extinction of hantkeninids and is thus used here to define the Eocene/Oligocene boundary (EOB) at 34.03 Ma. Calcareous nannofossil assemblages suggest a significant change from oligotrophic/warm surface waters during the late Eocene to eutrophic/cool waters during the early Oligocene. The observed changes in trophic conditions are synchronous with a shallowing trend testified by an increase in nearshore species and enhanced terrigenous input. Major environmental changes occurred at the EOB and across glaciation event Oi-1a whereas we record a poor imprint of glaciation event Oi-1. Three orbital configurations have been distinguished: (1) The late Eocene is characterized by a prominent 405-kyr cycle and a weak obliquity component; (2) the onset of cooling at 34.35 Ma coincides with the rosette-shaped discoaster extinction and is reflected by a shift toward enhanced obliquity and short-eccentricity cycles. The installation of a fully developed AIS (event Oi-1a, 32.75 Ma) shows the most pronounced obliquity imprint reflecting an increased influence of high-latitude climate processes; (3) after 31.75 Ma, the obliquity decreases in coincidence with the return to a dominant long-eccentricity cycle.

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SN - 2572-4517

VL - 35

JO - Paleoceanography and Paleoclimatology

JF - Paleoceanography and Paleoclimatology

IS - 8

M1 - e2020PA003887

ER -

The Eocene-Oligocene Transition in the South-Western Neo-Tethys (Tunisia): Astronomical Calibration and Paleoenvironmental Changes

Abstract

Bibliographical note

Keywords

ASJC Scopus subject areas

Access to Document

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