Sedimentary record of Mesozoic deformation and inception of the Turpan-Hami basin, northwest China

Todd J. Greene, Alan R. Carroll, Marc S. Hendrix, Stephan A. Graham, Marwan A. Wartes, Oscar A. Abbink

Research output: Contribution to journalArticlepeer-review

Abstract

The Turpan-Hami basin is a major physiographic and geologic feature of northwest China, yet considerable uncertainty exists as to the timing of its inception, its late Paleozoic and Mesozoic tectonic history, and the relationship of its petroleum systems to those of the nearby Junggar basin. To address these issues, we examined the late Paleozoic and Mesozoic sedimentary record in the Turpan-Hami basin through a series of outcrop and subsurface studies. Mesozoic sedimentary facies, regional unconformities, sediment dispersal patterns, and sediment compositions within the Turpan-Hami and southern Junggar basins suggest that these basins were initially separated between Early Triassic and Early Jurassic time. Prior to separation, Upper Permian profundal lacustrine and fan-delta facies and Triassic coarse-grained braided-fluvial-alluvial facies were deposited across a contiguous Junggar-Turpan-Hami basin. Permian through Triassic facies were derived mainly from the Tian Shan to the south, as indicated by northward-directed paleocurrent directions. This is consistent with the sedimentary provenance of Triassic sandstone (mean Qm29F29Lt42, Qp 23Lvm49Lsm28, and Qm51P 25K24) and conglomerate (∼32% granitic clasts) in the northern Turpan-Hami basin. We interpret a relative increase in quartz and feldspar concentration and a relative decrease in volcanic lithic grains in the northern Turpan-Hami basin to reflect unroofing in the Tian Shan and exposure of late Paleozoic granitoid rocks. In addition, two basinwide unconformities of Late Permian-Early Triassic and Early Triassic-middle-Late Triassic age attest to deformation within the Turpan-Hami basin and associated continued uplift and erosion of the Tian Shan. By Early Jurassic time, the Turpan-Hami basin and the southern Junggar basin became partitioned by uplift of the Bogda Shan, a major spur of the Tian Shan. In contrast to the thoroughgoing northward-directed Permian-Triassic depositional systems, Lower through Middle Jurassic strata begin to reflect ponded coal-forming, lake-plain environments within the Turpan-Hami basin. These strata contain paleocurrent indicators reflecting flow off the intervening Bogda Shan. Abasinwide Lower Jurassic- Middle Jurassic unconformity in the Turpan-Hami basin suggests continued uplift and erosion of the Bogda Shan, consistent with a return to more lithic-rich sandstone and volcanic-rich conglomerate compositions. These sedimentary facies, paleocurrent, and provenance data sets provide the best available constraints on the initial uplift of the Bogda Shan and the first documentary evidence of intra-Mesozoic shortening within the basin.

Original languageEnglish
Pages (from-to)317-340
Number of pages24
JournalMemoir of the Geological Society of America
Volume194
DOIs
StatePublished - 2001

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