Sea-land oxygen isotopic relationships from planktonic foraminifera and speleothems in the Eastern Mediterranean region and their implication for paleorainfall during interglacial intervals

摘要

The oxygen and carbon stable isotope compositions of cave speleothems provide a powerful method for understanding continental climate change. Here, we examine the question of the regionality of this isotopic record and its linkage with the marine isotopic record in the Eastern Mediterranean (EM) region. The study presents a new, accurately dated 250-kyr delta(18)O and VC record determined from speleothems of the Peqiin Cave, Northern Israel. Its comparison with the continuous 185-kyr isotopic record of the Soreq Cave speleothems from Central Israel reveals striking similarities. Thus, a strong regional climatic signal, brought about by variations in temperature and rainfall amount, is reflected in both cave records. Low delta(18)O minima in the Peqiin profile for the last 250- to 185-kyr period (interglacial marine isotopic stage 7) match the timing of sapropels 9 to 7 and are indicative of high rainfall in the EM region at these times. The combined Soreq and Peqiin 8180 record for the last 250 kyr excellently matches the published Globigerinoides ruber (G. ruber) marine delta(18)O record for the EM Sea, with the isotopic compositional difference Delta(G.ruber-speleothems) remaining relatively constant at -5.6 +/- 0.7%, thus establishing for the first time a robust, exploitable link between the land and the marine isotopic records. The correspondence of low delta(18)O speleothem values and high cave water stands with low G. ruber delta(18)O values during interglacial sapropel events indicates that these periods were characterized by enhanced rainfall in the EM land and sea regions. By use of sea surface temperatures derived from alkenone data as a proxy for land temperatures at the Soreq Cave, we calculate the paleorainfall delta(18)O values and its amounts. Maximum rainfall and lowest temperature conditions occurred at the beginning of the sapropel events and were followed by decrease in rainfall and increase in temperatures, leading to and conditions. The record for the last 7000 yr shows a trend toward increasing aridity and agrees well with climatic and archeological data from North Africa and the Middle East. Copyright (C) 2003 Elsevier Ltd. [References: 84]