DECIPHERING REGIONAL VERSUS GLOBAL CLIMATIC VARIATIONS USING PALEOSOLS: AN EXAMPLE FROM THE EARLY MIOCENE

Paleosols are an important tool in the paleoclimatic and paleoenvironmental interpretation of continental deposits and can provide a high resolution proxy for mean annual temperature and mean annual precipitation, particularly when there is a dearth of other paleoclimatic indicators, such as pedogenic carbonate or organic material. Early Miocene strata exposed at Sigena in the Ebro Basin, north-eastern Spain, have been identified as distal fluvial and lacustrine continental facies. Within the distal fluvial system, pedogenically altered channel and overbank deposits interfinger with ephemeral lacustrine facies. Paleosols were identified in the field on the basis of characteristics such as horizonization, ped morphology, root traces and ichnofossils, and whole-rock samples were analyzed using XRF. Results from geochemical climofunctions applied to these paleosols demonstrate that mean annual precipitation was the dominant control on paleosol type and indicate that the paleoclimate was considerably wetter during the Early Miocene, by up to 1150 mm yr-1 in comparison to modern values. The paleosols were formed in a sub-humid climatic regime rather than in an arid–semi-arid regime as previously suggested from sedimentological and paleontological research alone. By making comparisons with previously published data on paleoclimate during the Early Miocene, this presentation highlights the importance of regional climatic changes in global paleoclimatic interpretation.