Magnetostratigraphy of the fluvio-lacustrine sequence of core DY-1 in the Datong Basin and its implications for the evolution of the Shanxi Rift System in northern China

Abstract

The Shanxi Rift System is an intracontinental rift system located between the North China Plain and Ordos Plateau, which was infilled with thousands of meters of Cenozoic fluvio-lacustrine deposits. A comprehensive chronological framework will help better understand the formation and evolutionary process of the rift system. Here, we present a new magnetochronology for the Datong Basin sedimentary sequence in the northern Shanxi Rift System based on high-resolution magnetostratigraphic investigations of the DY-1 core. Correlation of the recognized magnetic polarity sequence of the DY-1 core with the Astronomically Tuned Neogene Time Scale shows that the fluvio-lacustrine sequence in the Datong Basin spans from Chron C3Bn to Chron C1n. The age of the Datong Basin sedimentary sequence can thus be paleomagnetically constrained to an interval from the late Late Miocene to Middle Pleistocene. The basal age of the sediments is ca. 7.0 Ma, which indicates that the initial extension of the northern segment of the Shanxi Rift System was no later than 7.0 Ma. The Datong Basin in the northern Shanxi Rift System has experienced a three-stage evolution: During the initial stage (7.0–4.2 Ma), fluvial environments are dominant. Then during 4.2–1.8 Ma, lacustrine environments are developed due to dip-slip fault activities, as part of the Nihewan paleolake. After 1.8 Ma, the lake gradually shrank. The northeastward progressive growth and expansion of the Tibetan Plateau may have driven the evolution of the Shanxi Rift System.