Publication Date:
2011-01-19
Description:
The Tian Shan range formed in the late Cenozoic in response to the northward propagation of deformation related to the India-Eurasia continental collision. Precise timing of the Tian Shan uplift is required to understand possible mechanisms of continental lithosphere deformation and interactions between climate, tectonism and erosion. Here, we provide magnetostratigraphic age control on the northern Chinese Tian Shan foreland successions. A thorough rock magnetic analysis identifies haematite- and magnetite-bearing alluvial fan deposits in the upper portion of the sampled strata as more reliable palaeomagnetic recorders than magnetite-bearing fluvial and lacustrine deposits that are often maghaemitized in the lower part of the record. As a result, a robust correlation to the geomagnetic polarity time scale is obtained from 6 to 2Ma while a tentative correlation is proposed from 6 to 16Ma. Sediment accumulation rates increase from 155 to 260mMyr-1 at 3.9±0.3Ma. This change coincides with a gradual lithologic transition from fluvial (sandstone-dominated) to alluvial fan (conglomerate-dominated) deposits that likely records an approaching erosional source related to tectonically increased subsidence rather than differential compaction. Clear evidence for growth strata starting at an estimated age of ∼2Ma provides a minimum age for folding. These results are compared with previous magneotstratigraphic studies from the same and other sections of the northern Tian Shan foreland basin fill, thus enabling a critical assessment of the reliability of magnetostratigraphic dating and the significance of sediment accumulation rate variations with respect to facies variations and growth strata. Our results in the Taxi He section provide a sequence of events that is consistent with enhanced tectonic forcing starting at ∼4Ma, although a climatic contribution must be considered given the close relationship of these ages with the Pliocene climate deterioration. © 2010 The Authors. Basin Research © 2010 Blackwell Publishing Ltd, European Association of Geoscientists & Engineers and International Association of Sedimentologists.
Print ISSN:
0950-091X
Electronic ISSN:
1365-2117
Topics:
Geosciences
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