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Sedimentary evolution of the foreland basin in the NE Tibetan Plateau and the growth of the Qilian Shan since 7 Ma

Hu Xiaofei, Chen Dianbao, Pan Baotian, Chen Jinjun, Zhang Jian, Chang Jing, Gong Changsheng and Zhao Qiming
Sedimentary evolution of the foreland basin in the NE Tibetan Plateau and the growth of the Qilian Shan since 7 Ma
Geological Society of America Bulletin (April 2019) Pre-Issue Publication

Abstract

We studied the magnetostratigraphy and sedimentary facies of a 550-m-long drill core from the Jiudong Basin in the NE Tibetan Plateau. Our aims were to reconstruct the late Cenozoic sedimentary evolution of this foreland basin, and to determine the spatiotemporal pattern of growth of the Qilian Shan. The magnetostratigraphy indicates that the sedimentary sequence was deposited during ca. 7-0 Ma. From ca. 6.7-3.0 Ma, the sediment accumulation rate increased gradually from approximately 30 mm/k.y. to 120 mm/k.y., which was associated with the gradual evolution of sedimentary facies from a shallow lake/delta front to braided rivers. The progradation of the depositional system from 7 Ma to 3 Ma probably reflects the growth of the relief of the Qilian Shan caused by tectonic uplift. The occurrence of a continuous braided river environment from 3 Ma to the present suggests that the high relief of the Qilian Shan developed before 3 Ma. An abrupt decrease of the sedimentation rate to approximately 46 mm/k.y. during 3.0-1.8 Ma, and the deposition of coarse-grained sediments, indicates the uplift of the basin center. We interpret this to reflect the propagation of the thrust system of the Qilian Shan into the basin along a southward-dipping decollement from ca. 3 Ma. Climatic changes may have influenced the sedimentary sequence by introducing long-distance-transported thin coarse sand/gravel layers which are sandwiched within the sequence, and likely were a response to cooling events or climatic transitions. The widespread occurrence of deformation within the basin region in the NE Tibetan Plateau at ca. 3 Ma indicates that this date marks the basinward growth of the deformation system.


ISSN: 0016-7606
EISSN: 1943-2674
Coden: BUGMAF
Serial Title: Geological Society of America Bulletin
Serial Volume: Pre-Issue Publication
Title: Sedimentary evolution of the foreland basin in the NE Tibetan Plateau and the growth of the Qilian Shan since 7 Ma
Affiliation: Lanzhou University, College of Earth and Environmental Science, Lanzhou, China
Published: 20190430
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 106
Accession Number: 2019-046847
Categories: StratigraphyStructural geology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: GSA Data Repository item 2019148
Illustration Description: illus. incl. 1 table, geol. sketch maps
N39°27'48" - N39°27'48", E99°25'60" - E99°25'60"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 2019
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