E/I-corrected inclination shallowing in Cenozoic redbeds from the northern Tarim Basin, NW China: Possible causes and paleogeographic implications

Because of their widespread occurrence and ability to carry stable remanence, continental redbeds in central Asia are frequently used in paleomagnetic studies. However, the paleomagnetic inclinations recorded by redbeds are much shallower than the expected values, as redbeds are usually subjected to inclination shallowing. To recognize and correct the inclinations recorded by the Cenozoic redbeds, the paleomagnetic data that were used for mag-netostratigraphic studies in the Kuqa Depression, northern Tarim Basin, are reanalyzed in this study. The mean inclinations of the four groups of samples (Eocene, Oligocene, Miocene, and Pliocene) are systematically similar to 20 degrees shallower than the expected values calculated from the apparent polar wander paths (APWPs) of Eurasia, indicating the presence of inclination shallowing. We apply the elongation/inclination (E/I) method to correct the inclination shallowing. The mean inclinations of the Eocene, Oligocene, Miocene, and Pliocene sedi-ments are corrected from 40.5 degrees to 63.1 degrees, 41.0 degrees to 63.8 degrees, 42.0 degrees to 63.8 degrees, and 44.7 degrees to 63.2 degrees, within 95% confidence limits between 55.1 degrees and 71.6 degrees, 53.7 degrees and 70.4 degrees, 51.5 degrees and 72.7 degrees, and 52.2 degrees and 71.3 degrees, respectively, which are indistinguishable from the expected inclination values. Our results suggest that inclination shallowing in the redbeds of central Asia can be reasonably corrected using the E/Imethod, and sedimentary processes such as compaction and/or imbri-cation in the very early stage of burial are important causes for inclination shallowing. Paleolatitudes calculated from the E/I-corrected inclinations show that the Tarim Basin should have reached or been at least close to its current latitude since the Cretaceous. The Cenozoic crustal shortening estimate of the northern Tarim Basin is not detectible for paleomagnetic study.