Late Cenozoic deformation and uplift of the NE Tibetan Plateau: Evidence from high-resolution magnetostratigraphy of the Guide Basin, Qinghai Province, China

Abstract

The Cenozoic intramontane GongheGuide Basin in Qinghai Province, China, is tectonically controlled by the sinistral strikeslip framework of the Kunlun and Altyn Tagh-South Qilian faults in the northeastern Tibetan Plateau. The basin is fi lled with thick Cenozoic clastic sedimentary formations, which provide important evidence of the deformation of this part of the plateau, although they have long lacked good age constraints. Detailed magnetostratigraphic and paleontologic investigations of fi ve sections in the Guide Basin and their lithologic and sedimentary characteristics allow us to divide a formerly undifferentiated unit (the Guide Group) into six formations (where ages are now magnetostratigraphically well established, they are given in parentheses): the Amigang (1.8-2.6 Ma), Ganjia (2.6-3.6 Ma), and Herjia formations (3.6 to ca. 7.0-7.8 Ma), and the older Miocene Ashigong, Garang, and Guidemen formations. These rocks document a generally upward coarsening sequence, characterized by increasing accumulation rates. Increasing gravel content and sizes of its components, changes of bedding dips and source rock types, and marginal growth faults collectively refl ect accelerated deformation and uplift of the NE Tibetan Plateau after 8 Ma, punctuated by a sharp increase in sedimentation rate at ca. 3.2 Ma that refl ects the boulder conglomerates of the Ganjia formation. Interestingly, much of the vergence of the compressional deformation in the basin is to the south, accommodated by a sequence of six thrusts (F1-F6), which become active one by one progressively later toward the south, undoubtedly contributing to the uplift of this part of the plateau. F1 likely initiated the Guide Basin due to crustal fl exure in the Oligocene, F2 was active in the early Miocene, F4 and F5 at ca. 3.6 Ma, and F6 was active in the early Pleistocene. The detailed late Miocene and younger magnetostratigraphy allows us to place much improved time constraints on the deformation and, hence, uplift of northeastern Tibet, which, when compared with ages for events on other parts of the plateau, provides important boundary conditions for the geodynamical evolution of Tibet.

Late Cenozoic orogenic history of Western Qinling inferred from sedimentation of Tianshui basin, northeastern margin of Tibetan Plateau

“…The transition in the sedimentary succession (9.2-7.4 Ma) expressed by the variation of depositional environment and the acceleration accumulation rates may be linked to tectonic uplift (e.g., Meyer et al 1998;Tapponnier et al 2001;Fang et al 2005;Dai et al 2006;Liu et al 2011) or climatic fluctuation (e.g., Zhang et al 2001). The pollen result of Yaodian section reported by Li et al (2006) shows that conifer-broadleaf mixed forest dominated the interval 11.7-7.7 Ma and the climatic change occurred only after 7.7 Ma.…”

Late Cenozoic continuous aridification in the western Qaidam Basin: evidence from sporopollen records

“…10e). The eastern part of the Qaidam Basin shows some evidence of tectonic activity at about ∼ 14.7 Ma events; the NW part after Zheng et al, 2000;Chen et al, 2002;Wang et al, 2003;Sun et al, 2004Sun et al, , 824 2005Sun et al, , 2007Sun et al, , 2009Charreau et al, 2005;2006;Huang et al, 2006;Heermance et al, 2007Heermance et al, , 2008825 Sun and Zhang, 2008;Tang et al, 2011 and; the NE part after Li et al, 1997;826 Song et al, 2001a, b;Zhao et al, 2001;Fang et al, 2003Fang et al, , 2005aZheng et al, 827 2006;Lin et al, 2010;Wang et al, 2010;and Wang et al, 2011a, b), and (g) the presumed 828 paleoaltimetry history after An et al (2006). 829 , tectonic uplift events in (e) the Qaidam Basin (rectangle showing the tectonic events; the western basin after Chang et al, 2012; the eastern basin after Fang et al, 2007, andXiong, 2009) and (f) the northern Tibetan Plateau (rectangles showing the tectonic events; the NW part after Zheng et al, 2000;Chen et al, 2002;Wang et al, 2003;Sun et al, 2004Sun et al, , 2007Sun et al, , 2009Charreau et al, 2005Charreau et al, , 2006Huang et al, 2006;Heermance et al, 2007Heermance et al, , 2008Tang et al, 2011, and; the NE part after ...…”

“…H. Song et al, 2001;Y. G. Song et al, 2001;Chen et al, 2002;Fang et al, 2003Fang et al, , 2005aWang et al, 2003;Sun et al, 2004Sun et al, , 2007Sun et al, , 2009Charreau et al, 2005Charreau et al, , 2006Huang et al, 2006;Heermance et al, 2007Heermance et al, , 2008Lin et al, 2010;Wang et al, 2010;W. T. Wang et al, 2011;Tang et al, 2011;Zhang and Sun, 2011;Nie et al, 2013) (Fig.…”

“…H. Song et al, 2001;Y. G. Song et al, 2001;Zhao et al, 2001;Fang et al, 2003Fang et al, , 2005aZheng et al, 2006;Lin et al, 2010;Wang et al, 2010;and W. T. Wang et al, 2011;, and (g) the presumed paleoaltimetry history after An et al (2006). ∼ 12 Ma (Lu and Xiong, 2009), ∼ 8.1 Ma and ∼ 3.6 Ma (Fig.…”

Disentangling the roles of late Miocene palaeogeography and vegetation – Implications for climate sensitivity

“…On land the palaeorecord suggests major uplift of the Himalayas (Fang et al, 2005;Harrison et al, 1992;Molnar et al, 1993;Rowley and Currie, 2006), the Andes (Garzione et al, 2008;Gregory-Wodzicki, 2002), the North American Rockies (Morgan and Swanberg, 1985), the East African Plateaus (Saggerson and Baker, 1965;Yemane et al, 1985), and the Alps (Kuhlemann, 2007;Spiegel et al, 2001) during the late Miocene. Figure S1 details the boundary condition used in our late Miocene simulations and highlights the major differences to the modern geography.…”