The relatively warm climate of the Miocene reached peak values during the middle Miocene Climatic Optimum (MMCO; 17-14.5 Ma). After the MMCO, the global climate started cooling. This happened through several short-lived cooling events, represented by positive oxygen isotope excursions: the Mi-events. These disturbances can be associated with growth of the East Antarctic Ice Sheet and potentially Northern Hemisphere ice expansion. The causes and consequences of the Mi-events are not well constrained. For this reason we want to examine the role of the Gulf Stream in the cooling and subsequent warming of the Mi-events, since it is a possible mechanism to amplify regional changes in northwestern Europe. Integrated Ocean Drilling Program (IODP) Leg 307 recovered a high resolution record from the middle Miocene of the Porcupine Basin, offshore southwestern Ireland and therefore under the influence of the Gulf Stream. We have extracted well-preserved palynomorphs (mainly organic-walled dinoflagellate cysts, acritarchs, some pollen) and organic molecules for paleothermometry (e.g. TEX (sub 86) and U (super K') (sub 37) ) from core 1318B. With these proxies the development of the Mi-3 and Mi-4 events are reconstructed on high resolution, by assessing e.g. temperature, sea level, thermocline depth and productivity. First results indicate a pronounced cooling as recorded simultaneously in TEX (sub 86) , U (super k') (sub 37) and dinoflagellate cyst assemblages during Mi-4. The presented results will focus in detail on the phasing and rates of change in the reconstructed Mi-events.

West: -11.4400 East: -11.3300 North: 51.2700 South: 51.2200

Expedition: 307

Provider: SEDIS Publication Catalogue

Data set link: http://sedis.iodp.org/pub-catalogue/index.php?id=2013-027514 (c.f. for more detailed metadata)

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