42. PLIOCENE-PLEISTOCENE PALEOENVIRONMENTAL HISTORY OF THE WESTERN MEDITERRANEAN: A SYNTHESIS OF ODP SITE 653 RESULTS1

• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: North Atlantic; Planktonic foraminifera
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.502.5451; http://www-odp.tamu.edu/publications/107_SR/VOLUME/CHAPTERS/sr107_42.pdf

Micropaleontological and oxygen isotopic studies of ODP Site 653 provide a nearly continuous and detailed record of the Pliocene-Pleistocene paleoenvironmental history of the Tyrrhenian Sea. Although the planktonic fauna and flora indicate that relatively warm conditions prevailed in the Mediterranean during the early Pliocene, the oxygen isotopic and paleontologic records show that this was not a period of "stable " climatic conditions. The first indications of a cooling trend in this region occur at approximately 4.1 Ma and 3.8 Ma with the introduction of a warm-temperate planktonic foraminiferal fauna and a major change in the calcareous nannofossil assemblage. The cooling trend is accentuated at approximately 3.1 Ma. At this time the warm water planktonic foraminiferal fauna is almost totally replaced by a temperate fauna, the cool water Coccolithus pelagicus shows a significant increase in abundance, and the oxygen isotope record shows a sudden cooling. During this part of the Pliocene, the benthic fora-miniferal fauna present in the Tyrrhenian Sea was very similar to the deep water fauna of the adjacent North Atlantic suggesting the existence of deep water exchange between these basins. The development of major Northern Hemisphere glaciation which has been well documented in the open ocean at approximately 2.4 Ma can easily be recognized in the Site 653 oxygen isotope record and in the sharp reduction in pro-ductivity of the discoasterids. The anti-estuarine circulation that characterizes the modern Mediterranean appears to have been established at this time. Another significant cooling is observed across the Pliocene-Pleistocene boundary, with cool water planktonic foraminifera becoming the dominant component of the overall assemblage. The Pleistocene 6180 record contains two modes of variability, a feature typical of open ocean records. The lower Pleistocene is dominated by low amplitude glacial/interglacial cycles, whereas the upper Pleistocene contains high am-plitude fluctuations.