Paleoclimatic investigations using isotopic signatures of the Late Pleistocene-Holocene groundwater of the stratified aquifers in Kuwait

Abstract

The study attempts to determine paleo recharge sources for two major aquifer units of Kuwait, namely, Kuwait Group Aquifer (KGA), and Dammam Formation (DFm) were collected and analyzed for major ions and isotopes. The obtained results of 14C ages indicated that the groundwater samples ranged from 31.9 Ky to 3.9 Ky in DFm and 23.3 Ky to 0.8 Ky in KGA. The variations in δ18O signatures with respect to age reflected that there were two major sources of rainwater such as enriched southern Indian Ocean monsoon and the depleted northwesterly (Mediterranean) vapor source. The samples found to show variations during the three marine isotopic stages (MIS 1–3), Heinrich events, Bolling-Allerod, and Dryas time periods in both aquifers. A shift in the Intertropical convergence zone (ITCZ) was witnessed in the groundwater of both aquifers from 7.8 Ky to 4.9 Ky. The variation in the Holocene climate is mainly due to the influence of tropospheric easterly jet governed by the swing in ITCZ , as a result of Holocene volcanism. The mean δ18O values of DFm samples (-3.81‰) reflect depletion than KGA samples (-2.31‰), and the d-excess values were −0.95‰ and 2.05‰ respectively. Thus it could be inferred that the DFm was predominantly recharged during Late Pleistocene period and it was in a relatively cooler climate than recharge environment of KGA. The study infers that KGA was recharged between 26oN and 26.8oN latitudes, and that of the DFm was noted to be recharged (south west of Kuwait) in two different patches between 25.8oN and 26.2oN and 26.7oN-27.4oN latitudes during Late Pleistocene. The KGA was concluded to be recharged between 25.5oN and 27.5oN latitudes, south of Kuwait, during Holocene.