A Stable Southern Margin of Asia During the Cretaceous: Paleomagnetic Constraints on the Lhasa‐Qiangtang Collision and the Maximum Width of the Neo‐Tethys

Abstract

The timing of the north-south collision between two terranes can be determined by the overlap of their paleolatitudes or the change of their convergence rate. For example, the overlapping paleolatitudes of the Lhasa terrane and Tethyan Himalaya and the dramatic decrease in the velocity of the Indian plate are usually ascribed to the India-Asia collision at~55 Ma. However, little is known about the paleolatitudinal evolution and velocity change of the Lhasa terrane resulting from the Lhasa-Qiangtang collision during the Jurassic-Cretaceous period. To better constrain the velocity change of the Lhasa terrane during this period, to constrain when and where the Lhasa-Qiangtang collision occurred, and to assess the distribution of land and sea in the Tethyan realm, we provide a high-quality Cretaceous paleomagnetic pole obtained from the limestone from the western part of the Lhasa terrane, which yields a paleolatitude of~16.8°± 1.9°N for the sampling area (32.2°N, 80.8°E) during the time interval of 113-72 Ma. We compile existing paleomagnetic results from the Lhasa terrane, Qiangtang terrane, Tethyan Himalaya, and India and reveal that the Lhasa-Qiangtang collision most likely occurred at or near the J/K boundary at~19°N for the reference point at (32°N, 88°E) and that the Neo-Tethys reached its maximum width (≥~7450 km) during this period.

New Paleomagnetic Results From Middle Jurassic Limestones of the Qiangtang Terrane, Tibet: Constraints on the Evolution of the Bangong‐Nujiang Ocean

“…The crystal sizes of the magnetic minerals in this study ranged from a few to tens of micrometers. The large magnetite grains may carry a stable remanence (Ma et al, ; Yang et al, ). The rock magnetic results and EDS analysis (Figures e–h) revealed that the magnetic minerals are mainly composed of magnetite and goethite.…”

“…However, the ChRM was obtained at temperatures higher than 120 °C in this study, the unblocking temperature of goethite. Furthermore, magnetite coexisting with Fe‐oxyhydroxides may represent initial detrital iron phases (Ma et al, ). These findings imply that magnetite may have a detrital origin (Abrajevitch & Kodama, ; Ma et al, ).…”

“…Furthermore, magnetite coexisting with Fe‐oxyhydroxides may represent initial detrital iron phases (Ma et al, ). These findings imply that magnetite may have a detrital origin (Abrajevitch & Kodama, ; Ma et al, ). Based on the above evidence, magnetite is interpreted as of detrital origin and the magnetic carrier of primary remanence in the studied section.…”

Precollisional Latitude of the Northern Tethyan Himalaya From the Paleocene Redbeds and Its Implication for Greater India and the India‐Asia collision

“…The remaining 16 poles consist of 199 volcanic and 167 sedimentary rocks sites (Table S2). Noticeably, though some of the studies showed that the Cretaceous sedimentary results from the Lhasa terrane might result from significant (Tan et al, ) or a small amount (Ma et al, ) of inclination shallowing, as well as Huang et al () provide good evidence that some Eocene sedimentary rocks from the Lhasa terrane have significant inclination shallowing, considering that the 199 reliable Cretaceous volcanic sites (groups) yield an inclination‐only mean of 27.6 ± 2.0° and a corresponding paleolatitude of 14.6° ± 1.2°N, which is consistent with 26.1 ± 1.7° and 13.8 ± 1.0°N deduced from the 167 reliable Cretaceous sedimentary sites (Tables and S2), we used the paleolatitude of 14.2 ± 0.8°N calculated from the inclination‐only mean for all the 366 reliable Cretaceous paleomagnetic sites (groups) as the precollisional paleolatitude for the southern margin of Asia (Figure ).…”

Paleomagnetism of the Late Cretaceous Red Beds From the Far Western Lhasa Terrane: Inclination Discrepancy and Tectonic Implications

“…Because the Lhasa terrane (LT) was located at the southern margin of Asia prior to India‐Asia collision (Figure 1a), reliable Cretaceous paleomagnetic data from the LT are essential to constrain the locations and geometries of the precollisional margins of Asia. However, the published Cretaceous paleomagnetic data sets from both volcanic and sedimentary rocks yielded a wide range of inclinations range from 17.7° to 41.9°, with the consequence that the obtained paleolatitudes vary from 9.9°N to 26.7°N (Cao, Sun, Li, et al, 2017; Ma et al, 2018; Pozzi et al, 1982; Sun et al, 2008, 2012; Tan et al, 2010; Tang et al, 2013; Tong et al, 2017; Yang, Ma, Zhang, et al, 2015; Yi et al, 2015). These conspicuous inconsistencies of Cretaceous paleolatitudes of the LT provided different geometries of the Asian southern margin prior to India‐Asia collision.…”