A biomarker isotope record of hydrologic change in NE Spain from the late Eocene to early Oligocene

Abstract:

The Eocene-Oligocene transition (EOT) (34-33.5 Ma) is one of the most dramatic climatic changes in the Cenozoic and represents a shift from global “hothouse” to “icehouse” conditions. Climatic and hydrologic data from across the globe indicate a high degree of heterogeneity in the terrestrial climatic response to this global cooling, with the largest changes observed at high latitudes. Recent data from northern Europe shows cooling across this interval associated with major faunal turnover. However, paleosol data from northeastern Spain suggests only modest changes to temperature and precipitation associated with this transition. We measured the hydrogen isotopic composition of higher plant-derived normal alkanes in Eocene to Oligocene sediments of Northeastern Spain to quantify changes to climate and isotope hydrology across this transition. Hydrogen isotopes of plant waxes provide a record of isotopes of precipitation and/or factors that influence stomatal regulation. Our data show a small increase in the average chain length of higher plant waxes across the EOT cooling event, which may reflect changes in water availability or ecosystem type. Hydrogen isotopes of higher plant waxes show a small positive shift in δD from the late Eocene to early Oligocene, but high-frequency variability prior to and after the Eocene-Oligocene transition. In total, when coupled with other paleoclimate proxy data, these suggest minimal changes to the hydrologic cycle in NE Spain from the late Eocene to early Oligocene.