A paleomagnetic study of the late paleocene sedimentary succession in the xigaze forearc basin, southern tibet, and its tectonic implications

Abstract

This study aims to constrain the paleolatitude of the southern margin of the Lhasa terrane during the late Paleocene and refine the constraints on intracontinental shortening within Asia resulting from the India–Asia collision. An integrated paleomagnetic and petrographic study was conducted on the upper Paleocene Jialazi Formation in the Xigaze forearc basin, southern Tibet. The limestone in the Jialazi Formation was demonstrated to reliably preserve primary remanence. Combined with previously published data, the tilt-corrected mean direction was Ds = 166.6° and Is = -38.2° with α₉₅ = 4.1 (n = 118), corresponding to a paleomagnetic pole at 75.3°N, 323.4°E, with an A₉₅ of 3.7°. Consequently, the paleolatitude of the Xigaze forearc basin from 56–59 Ma was estimated at ∼ 21.5°N for the reference point at 29.8°N, 84.9°E. Compared with data from the western Lhasa terrane, the Xigaze forearc basin and the Linzhou Basin, these findings suggest that the southern margin of the Lhasa terrane had an east–west orientation during the Late Cretaceous–early Eocene. A comparison with the apparent polar wander paths for Asia indicates that the intracontinental shortening between the Lhasa terrane and stable Asian interior has been 890 ± 470 km since the late Paleocene.