Title
Evidence of miocene crustal shortening in the North Qilian Shan from cenozoic stratigraphy of the Western Hexi Corridor, Gansu Province, China
Author
Bovet, P.M.
Ritts, B.D.
Gehrels, G.
Abbink, A.O.
Darby, B.
Hourigan, J.
TNO Bouw en Ondergrond
Publication year
2009
Abstract
New sedimentologic, stratigraphie, and compositional data from the Paleogene-Neogene stratigraphie succession exposed in the northwest Hexi Corridor and within the North Qilian Shan, provide evidence to suggest that crustal shortening in the North Qilian Shan fold-thrust belt initiated during die Miocene. The section is composed of four lithostratigraphic units: Oligocene-Miocene fine- to coarse-grained Unit 1, Miocene conglomeratic Unit 2, and Pliocene-Pleistocene conglomeratic Units 3 and 4. Unit 3 lies in angular unconformity over both Units 1 and 2, and Unit 4 contains a progressive unconformity. The onset of conglomerate deposition at the base of Unit 2 suggests an increase in depositional energy, which we interpret as me result of proximal orogenesis in the North Qilian Shan fold and tíirust belt. Supporting evidence includes the appearance of strongly northeast-trending paleocurrents, indicat-ing paleoflow away from the Qilian Shan, clast lidiologies that match sources in the North Qilian Shan, and sandstone with detrital framework modes that indicate a recycled orogen source. In contrast, Unit 1 contains paleocurrent indicators that are variable but generally trend northward and sandstone and clast compositions which are more diagnostic of a continental block source. Detrital zircon age determinations from Unit 1 are also not consistent with a source in the North Qilian Shan; rather, they suggest a provenance in hinterland regions within the South Qilian Shan and North Qaidam terranes. In sum, these results are all consistent with initiation of proximal uplift of the North Qilian Shan during deposition of the gradational transition from Unit 1 to Unit 2, demonstrating shortening in the Qilian Shan before die late Miocene. This comprehensive study tightens our understanding of when far-field stress related to the India-Eurasia continent-continent collision reached the northeastern edge of the Tibetan Plateau.
Subject
Geosciences
age determination
Cenozoic
conglomerate
crustal shortening
fold and thrust belt
lithostratigraphy
orogeny
sandstone
sequence stratigraphy
uplift
zircon
Asia
China
Eurasia
Far East
Qilian Mountains
Qinghai-Xizang Plateau
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TNO identifier
241474
ISSN
0002-9599
Source
American Journal of Science, 309 (4), 290-329
Document type
article