Reconstruction of the Middle Pleistocene climate of south Mediterranean using the Wadi Sannur speleothem, eastern Desert, Egypt

• Autores: Rifai I. Rifai
• Localización: Carbonates and Evaporites, ISSN 0891-2556, Vol. 22, Nº. 1, 2007, págs. 73-85
• Idioma: inglés
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• Resumen

  • The Wadi Sannur speleothems record climate changes spanning 188 and 136 kyr before present. Petrographically, the studied speleothem laminae are made up entirely of fibrous calcite except for one lamina that displays microspar fabric. Time-series analysis of the data set reveals regular changes in Sr/Ca and Mg/Ca at a scale that matches the thickness of the different laminae. d18O values of the stalactite laminae range from -7.2 to -10.1 VPDB%o The lower d18Ocalcite values, which are correspond to the second oldest lamina (WSS5), indicate that the drip-waters were likely affected by evaporative fractionation and that the speleothem activity has probably stopped due to the very arid conditions that followed the pluvial period. The variations of the d13C values between -5.0 and -2.3%o VPDB argue that the drip water composition is influenced by the interaction with the overlying grass-covered ecosystem and the degree of aridity rather than the bedrock (d13C -0.9%o VBDP).87Sr/86Sr ratios of the interglacial lamina are low (0.70781-0.70808), whereas the glacial lamina display higher ratios (0.70826-0.70859) in comparison with the nummulitic limestone bedrock (0.70753).