Cenozoic sediments in the southern Tarim Basin: implications for the uplift of northern Tibet and evolution of the Taklimakan Desert

Abstract

Cenozoic sedimentary successions along the southern margin of the Tarim Basin, western China, reach up to 10 km in thickness. The two studied sections, the Yecheng and Aertashi, comprise c. 4.5 km and c. 7.0 km of clastic sedimentary rocks respectively. The base of the Yecheng section has been dated palaeomagnetically to be about 8 Ma. Age control of the Aertashi section is based on 87Sr/86Sr measurements (for the basal marine bed), together with magnetostratigraphy and regional stratigraphic correlation. The lower part of each section is mainly composed of fine-grained mudstone and fine sandstone, which makes up the Wuqian Group (Miocene). The palaeoenvironment is low-energy, meandering and braided streams. The middle part is composed of red mudstone, sandstone with thin conglomerate beds, which make up the Artux Formation (Pliocene). The palaeoenvironment is a distal- to mid-fan environment. The uppermost part of the section, known as the Xiyu Formation (Plio-Pleistocene), consists of cobble and boulder conglomerate intercalated with massive siltstone lenses, which formed as proximal alluvial fan and aeolian deposits. Neogene red beds passing upward into upward-coarsening conglomerate and debris-flow deposits record the change in palaeoslope related to uplift of the northern margin of Tibetan Plateau.The formation of aeolian dunes at c. 8 Ma, and underlying playa lake deposits (as at Aertashi), may indicate an arid, enclosed basin in the southern Tarim after this time. Sedimentological characteristics, together with grain size distribution and geochemistry of siltstone bands in the Xiyu and Artux Formations, point to an aeolian origin. This indicates that the Taklimakan Desert and the regional climate regime may have been fully developed by the Early Pliocene. The onset of aeolian sedimentation in the southern Tarim Basin coincided with uplift of the northern Tibetan Plateau, as inferred from the lithofacies change. Tibetan Plateau uplift resulted in the shift of sedimentary environments northwards into the southern Tarim Basin, and could well have triggered the onset of full aridity in the Taklimakan region as a whole.

Miocene Volcaniclastic Sequence Within the Xiyu Formation from Source to Sink: Implications for Drainage Development and Tectonic Evolution in Eastern Pamir, NW Tibetan Plateau

“…(2) The clasts of Xiyu Conglomerate in the Kekeya section and the Aertashi section show totally different compositions, with the former dominated by angular to subangular sedimentary rocks and the latter dominated by rounded to subrounded igneous and matamorphic rocks. (3) Paleocurrent analyses of the Xiyu Formation yielded east to NW flow directions at Aertashi (Zheng et al, , and this study) and northward flow direction at Kekeya (Zheng et al, ). (4) Isopach maps of different units of the Neogene strata in the southwestern Tarim Basin indicate a depression to the NNE of Kekeya (Wei et al, ), inconsistent with the idea of sediments being supplied via Aertashi.…”

“…(3) Paleocurrent analyses of the Xiyu Formation yielded east to NW flow directions at Aertashi (Zheng et al, 2010, and this study) and northward flow direction at Kekeya (Zheng et al, 2006). (4) Isopach maps of different units of the Neogene strata in the southwestern Tarim Basin indicate a depression to the NNE of Kekeya (Wei et al, 2013), inconsistent with the idea of sediments being supplied via Aertashi.…”

Tectonic Evolution of the Pamir Recorded in the Western Tarim Basin (China): Sedimentologic and Magnetostratigraphic Analyses of the Aertashi Section

“…The western Tarim basin forms part of a relatively undeformed crustal block of Archean and Proterozoic metamorphic units overlain by Palaeozoic, Mesozoic, and Cenozoic marine to continental sedimentary rocks (e.g., Zheng et al, ). During the Cenozoic, the western Tarim basin has been subjected to overthrusting along its margin by the Tien Shan in the north, the Kunlun Shan in the south, and the Pamir in the west (e.g., Burtman & Molnar, ; Cowgill, ; Jia, ; Yin & Harrison, ).…”

“…In order to better constrain this evolution, we studied the Cenozoic Aertashi sedimentary section that constitutes the most complete and best‐dated sedimentary Cenozoic sequences from the western Tarim basin (e.g., Wei et al, ; Yin et al, ; Zheng et al, , , ). This work follows and complements previous dating and provenance results from this section (Blayney et al, ; Bosboom et al, , ) by providing (1) a sedimentological analysis of depositional environments, (2) magnetostratigraphic dating, (3) anisotropy of magnetic susceptibility analysis for stress orientation, (4) vertical‐axis rotation analysis, (5) backstripping analysis, and (6) additional provenance data in key intervals.…”

Early middle Miocene tectonic uplift of the northwestern part of the Qinghai–Tibetan Plateau evidenced by geochemical and mineralogical records in the western Tarim Basin

“…In the Tarim Basin ( Fig. 1), magnetostratigraphic studies have demonstrated that the Atushi Formation is >4.6-3.5 Ma in the Yecheng section (Zheng et al 2000(Zheng et al , 2010, ~5.3-3.0 Ma in the Sanju section (Sun and Liu 2006;Sun et al 2008), and >5.5-2 Ma in the western Boguzihe section (Zhang et al 2013). However, there is an angular unconformity between the Pakabulake and the overlying Atushi Formations in the Sanju section , while it is a conformable contact in the Yecheng and studied sections (Zheng et al 2000(Zheng et al , 2010.…”