Geochemical characteristics and depositional environment of the Shahejie Formation in the Binnan Oilfield, China

Trace elements in sedimentary rocks are highly sensitive to palaeoaquatic environmental changes in a sedimentary environment, making them an effective means for studying the paleoclimate and paleoenvironment during the deposition of sediments. The trace elements and major elements of mudstone cores sampled in the Binnan Oilfield in China were tested by inductively coupled plasma mass spectrometry (ICP-MS). Strontium (Sr), barium (Ba), vanadium (V), nickel (Ni) and boron (B), which are all sensitive to the sedimentary environment, were selected as discriminant indicators, and the sedimentary environment of the Shahejie Formation in the Binnan Oilfield was studied by combining with sedimentary indicators. The results show that the equivalent B content and the Sr/Ba ratio discriminate the research area for salt water and freshwater sedimentary environments. The V/(V + Ni) ratio is between 0.65 and 0.81, meaning that this area has a highly reductive sedimentary stratum. The trend of the Rb/Sr curve indicates that the paleoclimate of the Shahejie Formation changed from dry to humid and then back to dry.