Late Miocene northward propagation of the northeast Pamir thrust system, northwest China

Abstract

Piggyback basins on the margins of growing orogens commonly serve as sensitive recorders of the onset of thrust deformation and changes in source areas. The Bieertuokuoyi piggyback basin, located in the hanging wall of the Pamir Frontal Thrust, provides an unambiguous record of the outward growth of the northeast Pamir margin in northwest China from the Miocene through the Quaternary. To reconstruct the deformation along the margin, we synthesized structural mapping, stratigraphy, magnetostratigraphy, and cosmogenic burial dating of basin fill and growth strata. The Bieertuokuoyi basin records the initiation of the Pamir Frontal Thrust and the Takegai Thrust~5-6 Ma, as well as clast provenance and paleocurrent changes resulting from the Pliocene-to-Recent uplift and exhumation of the Pamir to the south. Our results show that coeval deformation was accommodated on the major structures on the northeast Pamir margin throughout the Miocene to Recent. Furthermore, our data support a change in the regional kinematics around the Miocene-Pliocene boundary (~5-6 Ma). Rapid exhumation of NE Pamir extensional domes, coupled with cessation of the Kashgar-Yecheng Transfer System on the eastern margin of the Pamir, accelerated the outward propagation of the northeastern Pamir margin and the southward propagation of the Kashi-Atushi fold-and-thrust belt in the southern Tian Shan. This coeval deformation signifies the coupling of the Pamir and Tarim blocks and the transfer of shortening north to the Pamir frontal faults and across the quasi-rigid Tarim Basin to the southern Tian Shan Kashi-Atushi fold-and-thrust system.

Neogene vegetation shift in the Nepalese Siwalik, Himalayas: A compound‐specific isotopic study of lipid biomarkers

“…A significant expansion of C 4 plants since 5.3 Ma has also been documented in Central Asia, north of the Tibetan Plateau (Sun et al, 2013;Shen et al, 2018). Collision and associated uplift of the Pamir Plateau and Tian Shan Ranges further blocked the eastward transport of the winter westerly moisture at the end of the Miocene (Thompson et al, 2015). The winter-season precipitation in the region, which is linked to westerlies carrying water vapour from the eastern Eurasian Paratethys Ocean, started to decline after ~8 Ma (Fortelius et al, 2014).…”

Latest Miocene to Quaternary deformation in the southern Chaiwopu Basin, northern Chinese Tian Shan foreland

“…The interpreted ~6 Ma tectonic event in the southern Chaiwopu Basin is nearly synchronous with deformation observed in the other sites of the Tian Shan [e.g., Huang et al ., ; Wang et al ., ; Sun et al ., ; Lu et al ., ], the Pamir [e.g., Thiede et al ., ; Thompson et al ., ], the Kunlun Shan [e.g., Zheng et al ., ; Sun et al ., ], and the northeastern Tibetan Plateau [e.g., Fang et al ., , ; Li et al ., ]. In foreland basins of the Tian Shan, acceleration of sediment‐accumulation rate and growth strata [ Huang et al ., ; Sun et al ., ; Lu et al ., ] and structural analysis [ Wang et al ., ] likewise identify the ~8–6 Ma uplift of the Tian Shan range and its resultant basinward encroachment.…”

Along‐Strike and Downdip Segmentation of the Pamir Frontal Thrust and Its Association With the 1985Mw6.9 Wuqia Earthquake

“…Its Quaternary slip rate, however, appears to be quite low (<1 mm/a), such that the regional convergence is now concentrated on the PFT, lying tens of kilometers north of the MPT (Arrowsmith & Strecker, ; Bufe et al, ; T. Li et al, , ; Thompson Jobe et al, ; Zubovich et al, ). The PFT initiated approximately 5–6 Ma, representing the latest, major forelandward propagation of the Pamir (Thompson et al, ). From west to east (Figure ), the fault is characterized by one or two splays in the Alai Valley, widens and branches into more splays at the eastern end of the Alai Valley, then connects with the primarily top‐to‐NE thrusts and folds at the western end of the Tarim Basin.…”