New paleomagnetic results from Late Ordovician rocks of the Yangtze Block, South China, and their paleogeographic implications

Abstract

AbstractThe paleogeographic relationship between South China and Australia during the Ordovician is important for understanding the configuration of South China in Gondwana. However, high‐quality Ordovician paleomagnetic results for the Yangtze Block are scarce. Here we report the results of a new paleomagnetic study of the Late Ordovician limestones of Wangcang County in the northern Yangtze Block, performed in order to constrain the paleoposition of South China. Two magnetic components were isolated by detailed stepwise thermal demagnetization. The low‐temperature component falls close to the local current Earth's field direction. The site‐mean direction obtained from the high‐temperature component (HTC) carried by magnetite is D/I = 132.6°/−35.2° (α95 = 3.6°) after bedding correction, yielding a paleomagnetic pole at 45.8°S, 191.3°E (dp = 2.4°, dm = 4.2°). The HTC direction passed reversal and fold tests, and its corresponding pole differs from the available paleomagnetic poles since the Silurian of the South China Block. These results suggest that the remanent magnetization was probably acquired during the earliest stage of sedimentation. The high‐temperature component yields a paleolatitude of 19.5°S, implying that the Yangtze Block was at tropic latitudes during the Late Ordovician. These new and reliable paleomagnetic results bridge the Ordovician data gap and favor the proximity between South China and Australia during the Late Ordovician.