A new Late Cretaceous to Present APWP for Asia and its implications for paleomagnetic shallow inclinations in Central Asia and Cenozoic Eurasian plate deformation

Abstract

Based on a compilation of 533 Cretaceous to present-day palaeomagnetic poles obtained from both sedimentary and igneous rocks, we present a new analysis of the so-called 'Asian inclination anomaly' and demonstrated the anomaly to be twofold: a 2nd-order anomaly, characterized by high palaeolatitudes in Indochina and low palaeolatitudes over Tibet and Central Asia, is superimposed on a 1st-order anomaly, characterized by Cenozoic low palaeolatitudes found all over northeastern Asian stable blocks. The analysis herein convincingly shows that the Europe Apparent Polar Wandering Path (APWP) can no longer be used to interpret palaeomagnetic data East of the Urals, including interpretation of Asian Tertiary deformation related to the India-Asia Collision. We, thus, construct a new APWP for East Asia, based on palaeopoles from blocks assumed to be stable. This new APWP is consistent with and reinforces previous analyses of Asian tectonics, such as the age (∼55 Ma) and locus (∼5-10°N) of the Indo-Asian collision, the lateral extrusion of SE Asian continental blocks and the intracontinental shortening in Central Asia. Possible origins of the 1st-order palaeolatitude anomaly are: (1) a geomagnetic origin, due to long-lasting non-dipolar contribution to the magnetic field and (2) a tectonic hypothesis, in which a newly defined East Asia Plate was located ∼10° farther south than expected from the current Europe APWP. Based on a set of six new reconstructions from 90 Ma to present, we show that our tectonic model reconciles geophysical, geological and tectonic observations throughout Eurasia, from Siberia to Europe, including kinematics in the Arctic Ocean, up to northwestern Arctic Alaska. Beyond possible occurrences of non-dipolar field contribution and/or local inclination flattening in the sedimentary data, our model leads us to conclude that Cenozoic tectonics is the dominant contributor to the observed 1st-order ∼10° low palaeolatitude anomaly over Asia during the Tertiary.