Magnetostratigraphy and paleoenvironmental record of late Cenozoic sediments in the Taiyuan Basin, North China

Abstract

The Taiyuan Basin is of importance for intraplate tectonic deformation in North China and contains Cenozoic strata with a maximum thickness of 3800 m. A ∼853.5-m-deep borehole (ZK01) with an overall core recovery rate of 85.09% was drilled at Yuci (37°35′37ʺN, 112°39′47ʺE) in the central Taiyuan Basin, to obtain high-resolution records of paleomagnetism, paleoclimatic and paleoenvironmental conditions, and depositional environment of the sediments. The obtained magnetic polarity sequence consists of 13 normal and 12 reverse zones, which correspond to C1n–C4An.2n of the geomagnetic polarity time scale. Magnetostratigraphic data show that the evolution of ZK01 core covers the interval from 8.1 Ma to the present, and the bottoms of Pliocene, Quaternary, and Middle Pleistocene were identified in Taiyuan Basin, with a sedimentary accumulation rate ranging from 62.5 m/Ma to 175.9 m/Ma. Geochemical data reveal that the source rocks in the study area underwent intense weathering and the sediments mainly formed in a semi-arid and oxygen-rich conditions. In addition, paleoclimatic changes occurred at ∼7 Ma, 3.8 Ma, and 1.7 Ma, which can be closely related to the tectonic uplift of the Loess Plateau and Tibetan Plateau, as well as the variations in the Asian monsoon and associated regional and global climatic change.