24 May 2023
 | 24 May 2023
Status: this preprint is open for discussion and under review for Climate of the Past (CP).

Middle Eocene Climatic Optimum (MECO) and its imprint in the continental Escanilla Formation, Spain

Nikhil Sharma, Jorge E. Spangenberg, Thierry Adatte, Torsten Vennemann, László Kocsis, Jean Vérité, Luis Valero, and Sébastien Castelltort

Abstract. The Middle Eocene Climatic Optimum (MECO) is a global warming event mainly described in the marine domain but less in the terrestrial domain. This study presents a comprehensive geochemical record of the MECO from the Escanilla Formation, a fluvial sedimentary succession in the southern Pyrenees, Spain, based on a suite of sampled paleosols, fluvial stromatolites and pedogenic nodules. Our multiproxy approach involves using carbon and oxygen stable isotope compositions to identify the regional preservation of the MECO, calculate chemical weathering intensity and identify the clay mineralogy of paleosols, as well as to estimate mean annual precipitation using temperature estimates based on clumped isotope compositions of carbonates. Results indicate that the Middle Eocene interval in the south central Pyrenees was characterized by low weathering rates under warm and arid climatic conditions. This is further supported by the presence of smectite, palygorskite, illite, and chlorite, which suggest seasonal rainfall but under generally dry conditions resulting in weak chemical weathering. Importantly, an isotopic excursion indicates a regional, terrestrial impact of the MECO, highlighting that fluvial sedimentary successions even in active foreland basins can represent particularly interesting terrestrial archives of past changes in global climate.

Nikhil Sharma et al.

Status: open (until 19 Jul 2023)

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Nikhil Sharma et al.


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Short summary
The Middle Eocene Climatic Optimum (MECO) is an enigmatic global warming event with scarce terrestrial records. To contribute to this issue, this study documents a new comprehensive geochemical record of the MECO in the fluvial Escanilla Formation, Spain. Results demonstrate continental sedimentary successions as key archives of past climate and stable isotopes as a powerful tool to correlate difficult to date fluvial successions.