Abstract The northeastern Arabian Peninsula has an extreme arid climate. To establish past variations in precipitation intensity during the late Quaternary, the oxygen isotope ratios (δ 18 O) of meteoric calcite cements of the late Quaternary aeolianites of the Ghayathi Formation in Abu Dhabi and Dubai have been analysed. The Ghayathi Formation is a carbonate-rich aeolianite, stabilised by calcite cement precipitated from rising groundwater during humid intervals. The calcite cements are well developed inside and outside a thin micrite rim of now hollow grains, formed by leaching of unstable carbonate grains. The δ 18 O values of cement analysed in thin sections by secondary ion mass spectrometry vary from −9.1‰ (VPDB) in coastal to +12.7‰ (VPDB) inland areas. This exceptionally wide range of the otherwise petrographically uniform aeolianite is due to the contrasts in humidity and evaporation rate between the coastal and inland areas. The δ 18 O values as low as −9.1‰ suggest intense precipitation in the late Quaternary, possibly due to the northward expansion of the intertropical convergence zone and intensified Indian summer monsoon. The exceptionally high values must be due to intense evaporation at low humidity in low-salinity, playa-type environments during intermittent arid intervals.
Sreenivasan et al. (Thu,) studied this question.
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