Middle Miocene environmental change : a multi-proxy study from the eastern Atlantic Ocean at the Porcupine Basin (IODP Leg 307)

• Main Authors: Quaijtaal, Willemijn, Schouten, Stefan, Donders, Timme, Louwye, Stephen
• Format: Conference Object
• Language: English
• Published: 2012
• Subjects: Earth and Environmental Sciences; Antarctic; East Antarctic Ice Sheet; Antarc*; Ice Sheet
• Online Access: https://biblio.ugent.be/publication/4414148; http://hdl.handle.net/1854/LU-4414148

During the Middle Miocene Climatic Optimum (MMCO; 17-14.5 Ma) the relatively warm climate of the Miocene reached peak values. 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. Associated events are East Antarctic Ice Sheet growth and potential Northern Hemisphere ice expansion. The causes and consequences of the Mi-events are not well constrained yet. For this reason we aim 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 or reduce regional changes in North-western Europe. Integrated Ocean Drilling Program (IODP) Leg 307 recovered a high resolution record from the Middle Miocene of the Porcupine Basin (offshore south-western Ireland), a region under influence of the Gulf Stream. We have extracted well-preserved palynomorphs (mainly organic-walled dinoflagellate cysts (see figure), acritarchs, some pollen) and organic molecules for paleothermometry (e.g. TEX86 and UK’37) from core 1318B. With these proxies, the development of the Mi-4 event is reconstructed on high resolution, by assessing e.g. temperature, sea level, thermocline depth and productivity. First results indicate a pronounced cooling during Mi-4 as recorded simultaneously in dinoflagellate cyst assemblages, TEX86 and Uk’37. The presented results will focus in detail on the phasing and rates of change in the reconstructed Mi-events.