Changing moisture sources over the last 330,000 years in Northern Oman from fluid-inclusion evidence in speleothems

Speleothems from Hoti Cave in northern Oman provide a record of continental pluvial periods over the last 330,000 yr. Periods of rapid speleothem deposition occurred from 6000 to 10,500, 78,000 to 82,000, 120,000 to 135,000, 180,000 to 200,000, and 300,000 to 330,000 yr ago, with little or no growth during the intervening periods. During each of these five pluvial periods, deltaD values of water extracted from speleothem fluid inclusions (deltaD(FI)) are between - 60 and - 20%o (VSMOW) and delta(18)O values of speleothem calcite (delta(18)O(c)) are between - 12 and -4% to (VPDB). These values are much more negative than modern rainfall (for deltaD) or modern stalagmites (for delta(18)O). Previous work on the isotopic composition of rainfall in Oman has shown that northern and southern moisture sources are isotopically distinct. Combined measurements of the deltaD values of fluid-inclusion water with calculated delta(18)O values from peak interglacial speleothems indicate that groundwater was predominantly recharged by the southern (Indian Ocean) moisture source, when the monsoon rainfall belt moved northward and reached Northern Oman during each of these periods. (C) 2003 University of Washington. Published by Elsevier Inc. All rights reserved.