APPLYING A MULTI-PROXY APPROACH TO THE DEVELOPMENT AND INFLUENCE OF A MEDITERRANEAN-TYPE CLIMATE ON THE IBERIAN PENINSULA

The five Mediterranean-type climates (MTC) host some of the most biodiverse ecosystems on the globe, collectively supporting one sixth of global flora. Today, the Mediterranean Basin experiences this climate, which is characterized by mild wet winters and hot dry summers. The combination of an MTC, environmental variation, geographical isolation, and heterogenous edaphic factors are thought to be responsible for the high biodiversity. However, this climate regime was not always in place, and is theorized to have appeared about 3.3 Ma, replacing a subtropical environment. In light of climate change threatening this water-limited region, it is important to understand the dynamics between climate shifts and the related vegetational responses. Does the vegetation change synchronously with the onset of a summer drought? Is there a vegetational response to climate shifts in the region? The purpose of this study is to apply stable oxygen isotope data from soil carbonates in Teruel, Spain as a paleo-rainfall proxy to advance understanding of the onset of the MTC in the basin. By evaluating stable oxygen isotopes from these carbonates, changes in the rainfall regime can be inferred. We can then compare this indicator of climate change with charcoal and previously published pollen and magnetic parameter records to better understand the vegetational-climatic relationship in this region. Our preliminary data shows a negative excursion of 1.8‰ from -5.2‰ to -7‰ at ~3.3 Ma, falling in line with the estimated onset of the MTC in this region and Marine Isotope Stage (MIS) M2, and a subsequent decrease of 1.5‰ from -4.7‰ to -6.2‰ during the onset of the Northern Hemisphere Glaciation (~3.1-2.7 Ma). These negative shifts in δ¹⁸O could result from a shift to winter-dominated rainfall, which has a lower δ¹⁸O value than summer rainfall, either through the onset of a summer drought or the intensification of winter rainfall through the southward shifted North Atlantic (NA) storm track during global cooling. Published work by our group of χ_fd records in the Teruel Basin suggest intensified precipitation during 3.3-3.18 Ma, which is synchronous with our recorded negative isotope excursion during the MIS M2 event and may provide support for the influence of a southward shifted NA storm track.