Comment on "Paleomagnetism of the Late Cretaceous Red Beds From the Far Western Lhasa Terrane: Inclination Discrepancy and Tectonic Implications" by Bian et al. Issue 4 (9th April 2021)

• Record Type: Journal Article
• Authors: Zhao, Qian; Huang, Baochun; Tao, Wei
• Is Part Of: Tectonics. Volume 40:Issue 4(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-04-09
• Subjects: finite strain -- inclination error -- Lhasa terrane -- magnetic fabric -- paleomagnetism; Geology, Structural -- Periodicals; 551.8
• DOI: 10.1029/2020TC006520
• Languages: English
• ISSNs: 0278-7407

Abstract

Abstract: Bian et al. (2020, https://doi.org/10.1029/2020TC006280 ) recently studied the paleomagnetism of the Late Cretaceous redbeds and summarized all the published paleomagnetic data obtained from the Lhasa terrane. A total of 25 poles from western and central‐eastern Lhasa terrane were collectively analyzed, of which they concluded 21 poles are reliable. These filtered directions, corrected for tilt and depositional biases following Tong et al. (2019, https://doi.org/10.1016/j.earscirev.2019.02.009 ), were then used to reconstruct the paleoposition and shape of the southern margin of the Asian continent. However, some of Bian et al.'s (2020, https://doi.org/10.1029/2020TC006280 ) interpretations are in conflict with the known geology of the Lhasa terrane. We argue that they have not applied the appropriate structural corrections to their data. The magnetic directions need to be corrected for a plunging fold axis and evaluated more thoroughly for post‐depositional strain. We recommend the data as presented in Bian et al. (2020, https://doi.org/10.1029/2020TC006280 ) should not be used for paleogeographic reconstructions. Moreover, cautions need to be given when applying paleomagnetic data with anisotropy of magnetic susceptibility analysis showing pencil structure to the deformational fabric to paleogeographic reconstructions. Key Points: The sampling unit and growth structure in the Geji area of western Lhasa are misidentified Tectonic strain contributes to the inclination discrepancy recorded in sedimentary rocks Only the data set showing primary or quasi‐primary sedimentary fabric can be used for paleogeographic reconstructions