Deciphering Paleocene‐Eocene Thermal Maximum Climatic Dynamics: Insights From Oxygen and Hydrogen Isotopes in Clay Minerals of Paleosols From the Southern Pyrenees

• Published in: Paleoceanography and Paleoclimatology 2024-11, Vol.39 (11), p.n/a
• Main Authors: Jaimes‐Gutierrez, Rocio, Adatte, Thierry, Pucéat, Emmanuelle, Vennemann, Torsten, Prieur, Marine, Wild, Amanda L., Khozyem, Hassan, Vaucher, Romain, Castelltort, Sebastien
• Format: Article
• Language: English
• Subjects: Air temperature; Annual precipitation; Annual rainfall; Annual temperatures; Arid climates; Body temperature; Catchment area; Catchment scale; Chemical composition; Chemical degradation; Chemical precipitation; Clay; clay mineralogy; Clay minerals; Climate change; Climatic conditions; Denudation; Earth Sciences; Eocene; Extreme values; Extreme weather; Flood discharge; Floodplains; Fractionation; Geochemistry; Global temperatures; Global warming; High temperature; Hydrogen; Hydrogen isotopes; Isotope composition; Isotopes; Limiting factors; Minerals; Oxygen; Oxygen isotopes; Palaeocene; Paleocene; paleoclimatology; Paleosols; PETM; Precipitation; Precipitation variability; Rainfall; Rocks; Sciences of the Universe; Sediments; Smectites; Soils; stable isotopes; Surface temperature; Temperature; Weathering
• ISSN: 2572-4517; 2572-4525; 2572-4525; 1944-9186
• DOI: 10.1029/2024PA004858

This study focuses on the Paleocene‐Eocene Thermal Maximum (PETM), a hyperthermal event characterized by a rapid increase in global temperature (5–8°C) over 20 ka, in the Southern Pyrenean Foreland Basin. Although there is evidence of increased flood discharge and erosion in the Southern Pyrenees, how paleoclimatic conditions and weathering evolved remains to be assessed. This study focuses on the catchment scale climatological changes recorded in the clay minerals of floodplain paleosols, giving insights into how rainfall affected the weathering regime during and after the hyperthermal event. The oxygen (δ18O) and hydrogen (δD) isotope compositions were analyzed in two clay fractions in paleosols of the Esplugafreda continental section. The clay minerals comprise a dominant smectite‐rich assemblage, which indicates a predominantly seasonal, semi‐arid climate throughout the section. Two positive excursions in the δ18O record during the Pre‐Onset Excursion (POE) and the Syn‐PETM support an increase in air near‐surface temperature. Using the δD and δ18O smectite fractionation factors, we estimate a Mean Annual Air Temperature (MAAT) of 24.2 ± 1.0°C for the POE and 27.0 ± 0.8°C for the Syn‐PETM. The δD values show a relatively stable composition during the climatic disturbance, which suggests that this mid‐latitude catchment was overall characterized by low yearly rainfall, with a peak in extreme events during the body of the PETM and a trend toward aridification during the recovery phase of the PETM, supported by the paleosol morphotype. These climatic conditions suggest a kinetically controlled weathering regime, where physical transport of the sediments played a primary role as a denudation mechanism. Plain Language Summary We investigate the Paleocene‐Eocene Thermal Maximum (PETM), a global warming event occurring 56 million years ago, and its local impact on the Spanish Pyrenees' climate. During the PETM, global temperatures rose by 5–8°C, prompting us to examine its influence on local mean annual temperature and precipitation. To understand how mountain rocks underwent physical and chemical breakdown into smaller, compositionally different minerals (weathering), we aim to unravel the processes of local climatic change during the PETM. Our study presents the hydrogen and oxygen isotopic composition of clay minerals in river floodplains, reflecting the climate in which they formed. A rise in heavy oxygen isotopes is observed before and during the PETM, co