Mid-Burdigalian Paratethyan alkenone record reveals link between orbital forcing, Antarctic ice-sheet dynamics and European climate at the verge to Miocene Climate Optimum

摘要

The Early Ottnangian Cooling (EOC), a distinct cold-spell in European climate at similar to 18 Ma preceding the Miocene Climate Optimum, is frequently reported in Paratethys records; however, the duration, magnitude, and underlying causes are poorly understood. A new palaeoclimatic data-set provides unexpected insights into this event. U-37(K')-based sea-surface temperatures > 24 degrees C between similar to 18.1 and 17.7 Myrs substantially exceed existing estimates, and indicate a significantly warmer European climate than previously assumed for this usually poorly recovered time interval. The EOC is expressed as an average drop of 2-3 degrees C in Paratethyan water temperatures between similar to 18.1 and 17.8 Myrs with two distinct cold snaps at similar to 17.86 Ma and similar to 17.81 Ma. The short duration of the EOC excludes Tethyan Seaway closure as its underlying cause, although the enhanced palaeoclimatic sensitivity of the Paratethys due to this palaeogeographic configuration potentially contributed to the magnitude of SST deterioration during the EOC. The revealed palaeoclimatic pattern shows a strong correlation with isotope event Mi-1b in deep-sea delta O-18 records, and we propose a tight palaeoclimatic link between the Southern Ocean and the Paratethys/Mediterranean realm as an alternative hypothesis. The interplay of modulations in the long-term (similar to 400 kyrs) and short-term (similar to 100 kyrs) eccentricity cycles most likely acted as pacemaker of this palaeoclimatic interaction. (C) 2014 The Authors. Published by Elsevier B.V.