Article, 2023

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

Palaeogeography Palaeoclimatology Palaeoecology, ISSN 0031-0182, 1872-616X, Volume 626, Page 111712, 10.1016/j.palaeo.2023.111712

Contributors

Messaoud, Jihede Haj 0000-0002-6825-7051 (Corresponding author) [1] Thibault, Nicolas Rudolph 0000-0003-4147-5531 [2] De Vleeschouwer, David 0000-0002-3323-807X [3] Monkenbusch, Johannes 0000-0002-0833-836X [2]

Affiliations

  1. [1] King Abdullah University of Science and Technology
    2. [NORA names: Saudi Arabia; Asia, Middle East];
  2. [2] University of Copenhagen
    3. [NORA names: KU University of Copenhagen; University; Denmark; Europe, EU; Nordic; OECD];
  3. [3] University of Münster
    4. [NORA names: Germany; Europe, EU; OECD]

Abstract

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.

Keywords

CaCO3, CaCO3 content, Earth, Eocene, Eocene Climatic Optimum, Eocene warming, Hilbert, Hilbert transform, Lower, Mediterranean, Middle Eocene Climatic Optimum, Nummulites, Southern, Spearman rank correlation, Tethyan, Tethyan margin, Tunisia, URL, Upper, abundance, abundance of benthic fauna, amplitude, amplitude modulation, analysis, archival, astrochronology, bed, benthic biota, benthic fauna, biota, carbon, carbon isotope excursion, carbonate platform, central Tunisia, climate, climatic optimum, components, conditions, content, control, control of climate, correlation, cycle, d18O, decomposition analysis, detrital input, eccentricity, eccentricity modulation, ecosystem, enhanced detrital input, environment, eustatic sea level, events, excursion, fauna, filter, flooding surfaces, formation, future environments, greenhouse, greenhouse conditions, high sea level, hyperthermal events, input, instantaneous amplitude, interval, isotope excursion, isotopes, levels, limestone units, low abundance, lowpass, lowpass filter, magnetic susceptibility, margin, marine ecosystems, marl interval, maximum abundance, maximum accumulation, maximum flooding surface, mesotrophic environment, middle, middle Eocene, modulation, nature, negative excursion, oblique component, optimum, peak, peak warming, platform, potential introduction, power, precession control, precession cycle, reaction, regional climate, response, sea level, sea-level cycles, sedimentary archives, shallow water carbonate platform, short eccentricity, site to site, sites, southern Mediterranean, stable isotopes, study, surface, susceptibility, time, transformation, tuning, units, variation, warming, warming climate, warming events, warming peak

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