Papers by Anne-Lise Develle
Quaternary Science Reviews, 2010
Late Quaternary paleoclimatic changes in the Levant are difficult to extract from carbonate oxyge... more Late Quaternary paleoclimatic changes in the Levant are difficult to extract from carbonate oxygen isotope records partly because the factors controlling the terrestrial d 18 O signals are not fully understood in this region characterized by sharp climatic gradients. Here, we address this purpose by presenting the first 14 C-dated isotope record from the northern Levant. The record is based on oxygen isotopes from ostracod shells from lacustrine-palustrine deposits accumulated in a small karstic, hydrologically open basin (Yammoû neh), located on the eastern flank of Mount Lebanon. We have first constructed a composite isotopic record obtained from three different ostracod taxa. This yields an oxygen isotope record of ostracods (d ost ) related to the most widespread species (Ilyocypris inermis), and converted to d 18 O values coeval with calcite precipitated in equilibrium (d C ) with the lake water (d L ). As with other records from the Mediterranean region, the Yammoû neh profile shows maximum and minimum d C values during the LGM and the early Holocene, respectively, and a slight late Holocene increase. In order to discuss the potential causes of the observed d 18 O values fluctuations (e.g., changes in the isotopic composition of the moisture source, temperature, precipitation minus evaporation (P-E) balance, or atmospheric circulation), we tentatively reconstruct the lake water isotope composition by correcting the d C values for lake water temperature using regional paleotemperature estimates. Inferred d L values were then corrected for the isotopic composition of the Eastern Mediterranean sea surface water (the moisture source) derived from planktonic foraminifera d 18 O values corrected for alkenone-based sea surface temperature. Our study suggests that Holocene d L fluctuations are primarily linked to changes in the sea surface water composition (source effect) amplified by enhanced inland rainfall during the early Holocene. During the LGM, low d L values at Yammoû neh are likely due to the ground-temperature effect on the rainfall isotope composition, possibly associated with a steeper altitudinal thermal gradient inland, and with changes in air mass trajectories over the Mediterranean Sea.
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Papers by Anne-Lise Develle