The growth of northeastern Tibet and its relevance to large‐scale continental geodynamics: A review of recent studies

Abstract

[1] Recent studies of the northeastern part of the Tibetan Plateau have called attention to two emerging views of how the Tibetan Plateau has grown. First, deformation in northern Tibet began essentially at the time of collision with India, not 10-20 Myr later as might be expected if the locus of activity migrated northward as India penetrated the rest of Eurasia. Thus, the north-south dimensions of the Tibetan Plateau were set mainly by differences in lithospheric strength, with strong lithosphere beneath India and the Tarim and Qaidam basins steadily encroaching on one another as the region between them, the present-day Tibetan Plateau, deformed, and its north-south dimension became narrower. Second, abundant evidence calls for acceleration of deformation, including the formation of new faults, in northeastern Tibet since~15 Ma and a less precisely dated change in orientation of crustal shortening since~20 Ma. This reorientation of crustal shortening and roughly concurrent outward growth of high terrain, which swings from NNE-SSW in northern Tibet to more NE-SW and even ENE-WSW in the easternmost part of northeastern Tibet, are likely to be, in part, a consequence of crustal thickening within the high Tibetan Plateau reaching a limit, and the locus of continued shortening then migrating to the northeastern and eastern flanks. These changes in rates and orientation also could result from removal of some or all mantle lithosphere and increased gravitational potential energy per unit area and from a weakening of crustal material so that it could flow in response to pressure gradients set by evolving differences in elevation.

Folded fluvial terraces in a young, actively deforming intramontane basin between the Yumu Shan and the Qilian Shan mountains, NE Tibet

“…The most recent (Mid-Late Quaternary in this study) lateral extension of the Yumu Shan and the deformation of the Dahe Fluvial terrace deformation in a young intramontane basin, NE Tibet | RESEARCH region reveal the lateral growth of the décol-lement on the NE edge of the Tibetan Plateau, which also suggests that from the north edge of the Qaidam to the Yumu Shan, the mountain ranges and intramontane basins have been gradually added to the crustal accretionary wedge since ca. 20 Ma (Yuan et al, 2013;Zheng et al, 2013b). The uplifting and folding of the Dahe region provide evidence that between the parallel mountain ranges on the NE Tibetan Plateau, intramontane basins (such as the Dahe region, the Heihe valley, the Changma He valley, and the Danghe valley) are also experiencing a certain amount of shortening and uplift above a south-dipping décollement.…”

“…1) and spans a width of ~350 km from south to north. The deformation structures in the orogenic belt were interpreted to record a gradual northward growth since the Early Miocene (Burchfiel et al, 1989;Tapponnier et al, 1990;Yuan et al, 2013). In interpreting the crustal shortening across this region, most studies have relied on fault slip rates for the thrust faults along the mountain edge (e.g., Hetzel et al, 2004Hetzel et al, , 2006Palumbo et al, 2009;Zheng et al, 2013aZheng et al, , 2013bZheng et al, , 2013c.…”

Relationship between the regional tectonic activity and crustal structure in the eastern Tibetan plateau discovered by gravity anomaly

“…Along the southern margin of the Qaidam basin, the Kunlun Mountain uplifted between *35 and *20-15 Ma (Fig. 1b) due to crustal shortening that occurred during that time along with the acceleration of exhumation near 15 Ma (Yuan et al 2013;Lu et al 2012). The initial left-lateral slip of the Kunlun fault zone began at *20-15 to *8 Ma on the E-W strike in the western part of the fault system (Jolivet et al 2003).…”

“…A major phase of exhumation of the Longmenshan fault zone started at 8-11 Ma (Godard et al 2009). The Kunlun fault zone is the northern boundary of Songpan-Garze fold belt, and the initiation age becomes younger toward the east (Yuan et al 2013). …”

“…Red lines are the locations of faults. QHNS Qinghainanshan fault, GHNS Gonghenanshan fault, LJS Lajishan fault, JSS Jishishan fault, KLF Kunlun fault, DBWDF Diebu-Bailongjiang fault, XREF Xiarier fault, TZF Tazang fault, AWCF Awancang fault, LRBF Longriba fault zone, XSF Xueshan fault, MJF Minjiang fault, HYF Haiyuan fault, QCF Qinchuan fault, LMSFZ Longmenshan fault zone, GZYSF Garze-Yunshu fault, XSHF Xianshuihe fault, XJF Xiaojiang fault (Modified from Tapponnier et al 2001;He and Chéry 2008;Yuan et al 2013;Ren et al 2013;Guo et al 2015) a whole and focused on the regional crustal feature in a map view to determine the lateral contact relationship between crustal structure and tectonic activity.…”