Paleomagnetic results from the Upper Permian of the eastern Qiangtang Terrane of Tibet and their tectonic implications

Abstract

Paleomagnetic samples were collected from red intercalations within the Upper Permian Tuoba Formation from the eastern Qiangtang Terrane of Tibet. Progressive thermal demagnetization has revealed a prefolding, possibly primary, characteristic remanent magnetization (ChRM), which yields a tilt-corrected mean direction ofD/I=25.2°6.7° (α 95 = 8.6°). The equatorial paleolatitude for the Qiangtang Terrane indicated by this result and the similarity of Late Permian fauna and flora shared by the Qiangtang Terrane and South China Block (SCB) suggest that the two terranes were in close proximity during the Late Permian. A Late Permian paleogeographic reconstruction involving the major terranes of the present-day East Asia is constructed, in which the Songpan-Garze Sea is surrounded by Laurasia, the North China Block (NCB), the SCB and the Qiangtang Terrane. The Permian development of the Songpan-Garze Sea appears to be related to the rifting of the Qiangtang Terrane off the SCB. Its Triassic evolution may resemble that of the Solomon Sea today in the southwestern Pacific.