CLIMATIC ZONING OF THE ATLANTIC, INDIAN AND PACIFIC OCEANS IN THE MIDDLE AND LATE MIOCENE

Abstract

To reconstruct the evolution of the climate, the authors mapped its zoning on the basis of planktonic forminifera characteristic of the end of the middle and the end of the late Miocene. The position of climatic zones in the three oceans was reconstructed by the palinspastic method [13] for the 10- and 5-m.y levels. The authors used the procedure employed for the Pliocene and the early Miocene [7-9], taking into account previous estimates of surface-water paleotemperatures derived from oxygen-isotope data. Results indicate that the middle and late Miocene climate was warmer than at present. Between 12.5 and 5.3 m.y. ago, the climate was more contrasting. During the middle and the late Miocene the southern hemisphere was colder than the northern, as indicated by the asymmetric position of the bipolar climate zones. Surface circulation in the ocean became more intense during the middle and the late Miocene, acquiring the broad features of its present pattern; there were analogs of many of the present currents and upwellings. However, the tradewind current flowed from the Atlantic into the Pacific through the Panama strait.