Paleotemperature Reconstruction Using Environmental Isotopes and Noble Gases in Groundwater in Morocco

A Turonian limestone-dolomite aquifer from the Tadla basin of Morocco was analysed using a multi-tracer approach (δ 18 O, δ 2 H, δ 13 C, 3 H, 14 C and noble gases) to reconstruct the paleotemperature evolution from the late Pleistocene to the Holocene. The Turonian aquifer was found to be suitable for a groundwater-based paleoclimate reconstruction, representing the Holocene–late Pleistocene epochs. After correction for young water contribution, mean residence times (MRTs) of groundwater were calculated using the Pearson radiocarbon model. Additionally, terrigenic helium content was used as an age indicator. Noble gas temperature (NGT) results from wells with groundwater ages corresponding to glacial periods showed an average of 17.2 ± 1.7°C. In contrast, samples of recent recharge water gave a mean NGT of 25.2 ± 1.3°C. This reveals a temperature difference of 8.0 ± 2.1 °C between the Holocene and late Pleistocene. This significant Pleistocene–Holocene temperature difference observed in Africa has considerable significance and can be extended to address an important topic relating to the nature of the wet epochs during which the fossil aquifers of North Africa were recharged. It is evident that this aquifer was recharged during both interglacial (warm) and glacial (cool) wet periods.