Geochemistry and mineralogy of Quaternary sediments in the northern Bohai Bay Basin, North China: implications for provenance and climate change

Abstract

The Bohai Bay Basin, located in the eastern North China Block, is an important sedimentary basin for studying the Quaternary climate and environment of northern China. Although sporo-pollen analyses have been used to study the paleoclimate, quantitative research via geochemistry had not been conducted. The sedimentary sequence, geochemistry, and mineralogy of Quaternary sediments from core GJ01 in the Yongding River fluvial plain, northern Bohai Bay Basin, were studied to determine their provenance and investigate climate change during the Quaternary. The stratigraphic sequence of the Quaternary was mainly formed by fluviation by a meandering river, showing a typical dual structure. The sediments have relatively high SiO2 and CaO concentrations, and low Al2O3, Na2O, and Fe2O3T concentrations. In terms of trace elements, most large ion lithophile elements are slightly enriched, and Rb and K concentrations are close to those of post-Archean Australian shale (PAAS); most high field strength elements are slightly to moderately depleted. Rare earth elements (REEs) vary significantly, with light rare earth elements (LREEs) obviously enriched relative to heavy rare earth elements (HREEs). A slightly negative Eu anomaly is present, with nearly no Ce anomaly. Mineralogical analysis shows that the main minerals in the fine-grained sediments are quartz, plagioclase, and K-feldspar. The geochemistry and mineralogy of the sediments indicate that the main provenances were recycled sedimentary rocks and felsic igneous rocks. The sediments have low chemical index of alteration (CIA) values, demonstrating that the source rocks underwent slight weathering. The mean annual precipitation and temperature of the studied area during the Quaternary varied from 531 to 875 mm and from 4.1 to 11.8 °C, respectively.