Paleoclimate interpretation in northern Ordos Basin: Evidence from isotope records of groundwater

The hydrogen and oxygen stable isotopes are the indicative evidences of paleoclimate change. δD and δ18O composition of groundwater is commonly used to provide information on the climate record. This study focuses on the isotopic evidences of paleoclimate variations in the Northern Ordos Basin, where the Cretaceous groundwater have different ages since the middle age of Late Pleistocene. The hydrogen/oxygen stable isotopic compositions are analyzed and groundwater age is calculated by 14C based on 59 groups of data collected from 16 boreholes in the study area. The δD and δ18O data indicate that the temperature is relatively low in the middle age of Late Pleistocene, and it became to get warmer since the Holocene, which coincides with the variation of global scale. It is also found that the δD and δ18O could be divided into two groups in terms of groundwater age, the Holocene (<15 ka BP) and the middle stage of Late Pleistocene (31-19 ka BP). There exists a remarkable gap of groundwater age in the late stage of Late Pleistocene (19-15 ka BP), which corresponds to the last glacial maximum (LLM), it is concluded that this gap may be caused by the periglacial covered over the northern of Ordos Basin in these period when the groundwater recharge from precipitation is prevented by ice sheet or frozen soil. The results obtained in this study will provide useful insights for paleoclimate reconstruction in Ordos Basin.