Eocene (50-55 Ma) greenhouse climate recorded in nonmarine rocks of San Diego, CA, USA

This is a Preprint and has not been peer reviewed. The published version of this Preprint is available: https://doi.org/10.1038/s41598-024-53210-0. This is version 3 of this Preprint.

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Adrian Broz , Devin Pritchard-Peterson, Sarah Schneider, Diogo Spinola, Greg Retallack, Lucas C.R. Silva


Nonmarine rocks in sea cliffs of southern California store a detailed record of weathering under tropical conditions millions of years ago, where today the climate is much drier and cooler. This work examines early Eocene (~50-55 million-year-old) deeply weathered paleosols (ancient, buried soils) exposed in marine terraces of northern San Diego County, California, and uses their geochemistry and mineralogy to reconstruct climate and weathering intensity during early Eocene greenhouse climates. These Eocene warm spikes have been modeled as prequels for ongoing anthropogenic global warming driven by a spike in atmospheric CO2. Paleocene-Eocene thermal maximum (PETM, ~55 Ma) kaolinitic paleosols developed in volcaniclastic conglomerates are evidence of intense weathering (CIA >98) under warm and wet conditions (mean annual temperature [MAT] of ~17° C ± 4.4° C and mean annual precipitation [MAP] of ~1500 ± 299 mm). Geologically younger Early Eocene climatic optimum (EECO, 50 Ma) high shrink-swell (Vertisol) paleosols developed in coarse sandstones are also intensely weathered (CIA >80) with MAT estimates of ~20 °C ± 4.4° C but have lower estimated MAP (~1100 ± 299 mm), suggesting a less humid climate for the EECO greenhouse spike than for the earlier PETM greenhouse spike.




Chemistry, Climate, Earth Sciences, Geochemistry, Geology, Physical Sciences and Mathematics, Soil Science, Stratigraphy


San Diego, Paleosols, Paleocene-Eocene Thermal Maximum, Early Eocene Climatic Optimum, kaolinite, Deep Weathering Profile


Published: 2023-08-08 10:17

Last Updated: 2023-09-22 18:25

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