Middle Miocene temperature and productivity evolution at a Northeast Atlantic shelf site (IODP U1318, Porcupine Basin) : global and regional changes

We present a high-resolution multiproxy middle Miocene sea surface temperature (SST) and productivity (SSP) reconstruction of Integrated Ocean Drilling Program Site U1318, from the upper slope edge (similar to 400 m water depth) of the Porcupine Basin continental margin, eastern North Atlantic Ocean. Biomarker and dinoflagellate cyst proxies reveal warm and mostly stratified waters during the Miocene Climatic Optimum (MCO) that cooled similar to 3 degrees C across the Miocene Climate Transition (MCT). The organic biomarker (TEX86 and UK ' 37) paleothermometers document a series of 11 transient cooling events (CEs), superimposed on the long-term climate evolution. These CEs are associated with increases in cold-water dinocysts and correlate to global benthic delta O-18 shifts, including the Mi-2, Mi-3, and Mi-4 events. Most CEs are also associated with increases in primary productivity. A prolonged interval of high SSP between similar to 13.8 and 13.6 Ma supports the idea that carbon production (and burial) in shallow areas represents a feedback mechanism contributing to long-term atmospheric CO2 decline and cooling during the MCT. SST comparison in three North Atlantic sites (Azores Site 608, Porcupine Basin Site U1318, and Rockall Plateau Site 982) reveals that MCO SSTs are much warmer at Site 608 than at the other two sites. The low-resolution SST record of Site 982 shows no decrease in temperature around the MCT. This may be linked to contemporaneous tectonic changes in the Tethys, Central American, and Arctic Seaways impacting local ocean circulation, superimposed on global drivers of climate change