Palaeomagnetic results from Palaeogene red beds of the Chuan-Dian Fragment, southeastern margin of the Tibetan Plateau: implications for the displacement on the Xianshuihe–Xiaojiang fault systems

Paleomagnetic Evidence for 25–15 Ma Crust Fragmentation of North Indochina (23–26°N): Consequence of Collision With Greater India NE Corner?

“…Geochemistry, Geophysics, Geosystems (mostly from the Lanping domain) the primary remanence is preserved and was unblocked over 640-680°C as the HT component. A similar dual polarity-presumably primary remanence unblocked in the 610-670°C to 690°C temperature range has been consistently reported from all domains of north Indochina (Chen et al, 1995;Huang & Opdyke, 1993;Kondo et al, 2012;Sato et al, 2001;Tanaka et al, 2008;Tong et al, 2013Tong et al, , 2015Tong et al, , 2016Wang, Yang, et al, 2016;Yoshioka et al, 2003). Given this pattern, it is surprising that the ChRMs from Lanping domain edges seem to preserve a primary magnetization, implying that no CRM overprint occurred here.…”

“…We make clear that the HT components were calculated by connecting only two demagnetization points (640 and 680 °C); thus, we admit that the HT component directions of our data set may be slight biased. However, several studies of red beds from Indochina have showed that the HT component is usually defined at a temperature range varying between 600–680 °C and 640–680 °C, never found to be higher than 670–690 °C (Chen et al, ; Huang & Opdyke, ; Kondo et al, ; Sato et al, ; Tanaka et al, ; Tong et al, , , ; Wang, Yang, et al, ; Yoshioka et al, ). Figure shows that—considering samples where a HT occurs—remanence directions change slightly from 600 to 640 °C, testifying the final unblocking of the MT components.…”

“…Several paleomagnetic 10.1029/2019GC008308 Geochemistry, Geophysics, Geosystems studies of north Indochina red beds report a paleomagnetic overprint-inferred by the occurrence of ubiquitous normal polarities in rocks of wide age ranges-coupled with a positive fold test, suggesting a pretilting (i.e., pre-25-15 Ma) remagnetization (Funahara et al, 1993;Gao et al, 2015Gao et al, , 2017Li, Yang, et al, 2017;Sato et al, 1999Sato et al, , 2007. However, other studies reported also dual polarities, and isolated a (presumably primary) remanence unblocked at very high temperatures, in the 610-670°C to 690°C temperature range (Chen et al, 1995;Huang & Opdyke, 1993;Kondo et al, 2012;Sato et al, 2001;Tanaka et al, 2008;Tong et al, 2013Tong et al, , 2015Tong et al, , 2016Wang, Yang, et al, 2016;Yoshioka et al, 2003).…”

“…Figure shows a general predominance of variable magnitude CW rotations from Jurassic‐Oligocene rocks, and Neogene sediments and deposits show barely significant rotations. The Chuandian domain yields a rather clear pattern of 15–20° CW rotations for Cretaceous‐Oligocene red beds (Funahara et al, ; Gao et al, ; Li et al, , ; Otofuji et al, ; Tong et al, ; Wang, Yang, et al, ; Yang, Sun, et al, ; Yoshioka et al, ; Zhu et al, ). Jurassic‐Oligocene red beds from the Baoshan, Lanping, and northern Simao domains provide highly variable CW rotations, in few cases exceeding 90° (Chen et al, ; Funahara et al, ; Gao et al, ; Huang & Opdyke, , ; Kondo et al, ; Li, Yang, et al, ; Li et al, ; Sato et al, , , ; Tanaka et al, ; Tong et al, , ; Yang, Yin, et al, ; Yang, Sun, et al, ).…”

New insights into the Cenozoic lateral extrusion of crustal blocks on the southeastern edge of Tibetan Plateau: Evidence from paleomagnetic results from Paleogene sedimentary strata of the Baoshan Terrane

“…However, the recent GPS and geodetic data set for areas internal to and surrounding the Tibetan Plateau indicate that crustal materials currently experience significant clockwise rotation around the Eastern Himalaya Syntaxis, along several N‐S trending fault systems, for example, the Xianshuihe‐Xiaojiang strike‐slip fault belt and the Dien Bien Phu strike‐slip fault belt and others. [ Chen et al ., ; Shen et al ., ; Gan et al ., ; Wang et al ., , ].…”