Benthic biota (nummulites) response to a hyperthermal event: Eccentricity-modulated precession control on climate during the middle Eocene warming in the Southern Mediterranean

Jihede Haj Messaoud*, Nicolas Thibault, David De Vleeschouwer, Johannes Monkenbusch

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Earth's future environment depends critically on how the marine ecosystems react to the current greenhouse conditions. Past warming events from the Middle Eocene can shed light on the nature of these reactions. Middle Eocene sedimentary archives from the Tethyan margins record the Middle Eocene Climatic Optimum (MECO) with varying carbon isotope excursions from site to site. The present study integrates stable isotopes, the abundance of benthic fauna, and astrochronology to look for the timing of the MECO peak warming and the maximum abundance of nummulites in the Southern Mediterranean (Tunisia). A mesotrophic environment during the lower Bartonian with high eustatic sea level promotes the formation of a shallow water carbonate platform in central Tunisia from 40.6 Ma to 39.8 Ma. Nummulites occur in low abundance in the Lower Reneiche Limestone unit (LRL, Bey et al., 2015) from 40.6 to 40.2 Ma, then increase, reaching maximum abundance at the Upper Reneiche Limestone unit (URL, 40.1 to 40 Ma). Maximum accumulation of nummulites and negative excursion of δ18O in the URL occurred during the MECO's warming peak (40.07 to 40 Ma), 200 kyr after the middle Eocene third-order maximum flooding surface. The nummulitic beds represent warmer climates and higher sea levels (arid to semi-arid climate), and the short marl intervals reflect enhanced detrital input (humid climate and lower sea level). The eccentricity modulations were extracted using a lowpass filter applied on a wide-band precession filter then we computed the instantaneous amplitude using Hilbert Transform. The Spearman-rank correlation assesses the potential introduction of amplitude modulations during tuning. Power Decomposition Analysis (PDA) indicates a dominant short eccentricity forcing on the regional climate during the MECO with a minor obliquity component. Variations in magnetic susceptibility and CaCO3 content suggest a combined control of climate and sea-level cycles controlled by eccentricity-modulated precession cycles.

Original languageEnglish (US)
Article number111712
JournalPalaeogeography, Palaeoclimatology, Palaeoecology
StatePublished - Sep 15 2023

Bibliographical note

Funding Information:
Funding for this study was ensured through internal funds from the University of Copenhagen allocated to J.H.M. via the double-degree Ph. D. program. We are very grateful to Prof. Frans van Buchem and the anonymous reviewers for the insightful revisions furnished. This manuscript contributes to the IGCP 739 project (Mesozoic - Paleogene hyperthermals events).

Publisher Copyright:
© 2023 Elsevier B.V.


  • Carbon isotope
  • MECO
  • Milankovitch cycles
  • Nummulites
  • Orbital-driven paleoenvironmental changes
  • South Mediterranean

ASJC Scopus subject areas

  • Oceanography
  • Ecology, Evolution, Behavior and Systematics
  • Earth-Surface Processes
  • Palaeontology


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