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Abstract
Wang, Xin, John Suppe, Shuwei Guan, Aurelia Hubert-Ferrari, Ramon Gonzalez-Mieres, and Chengzao Jia,
DOI:10.1306/13251339M94389
2011 by The American Association of Petroleum Geologists.
Cenozoic Structure and Tectonic Evolution of the Kuqa Fold Belt, Southern Tianshan, China
Xin Wang,1 John Suppe2 Shuwei Guan,3 Aurelia Hubert-Ferrari,4 Ramon Gonzalez-Mieres5 Chengzao Jia6
1Department of Geosciences, Zhejiang University, Hang Zhou, China
2Department of Geosciences, National Taiwan University, Taipei, Taiwan; Also at: Department of Geosciences, Princeton University, Princeton, New Jersey, U.S.A.
3Research Institute of Petroleum Exploration and Development, PetroChina, Beijing, China
4Geomorphologie, Universite de Liege, Liege, Belgium
5Department of Geosciences, Princeton University, Princeton, New Jersey, U.S.A.; Present address: Saudi Arabian Chevron, Chevron Global Upstream and Gas, Houston, Texas, U.S.A.
6Research Institute of Petroleum Exploration and Development, PetroChina, Beijing, China
ACKNOWLEDGMENTS
This research was funded by the Tarim Oilfield Company of PetroChina, the China National Science Fund (grants 49972077 and 40372090), the U.S. National Science Foundation (grant EAR-0073759), Princeton University 3-D Structure Project, and the Swiss National Science Foundation (grant SNSF20020-101781). This research would have been impossible without the cooperation of the Tarim Oilfield Company that provided seismic and well data and supported our field work. We are particularly grateful to Lu Huafu of Nanjing University and Wang Zhaoming, Pi Xuejun, Li Qiming, Xie Huiwen, Pen Genxin, and Lei Ganlin of Tarim Oilfield Company for their hospitality and support of this work. Suppe is grateful for the hospitality of the Ludwigs-Maximillian University Munich and support of the Alexander Von Humboldt Foundation during the preparation of this manuscript.
ABSTRACT
The east–west-trending late Cenozoic Kuqa fold belt is a part of the compressive southern margin of the Tianshan Mountains in western China. Approximately 20,000 km (12,000 mi) of two-dimensional seismic reflection profiles are integrated with surface geology and well data to examine the deformation style and structural
evolution of the Kuqa fold belt. Mesozoic through Holocene strata in the northern Tarim Basin have been deformed in a thrust system that roots northward into the Paleozoic basement of the southern Tianshan. The south-vergent deformation is characterized by a series of forward-breaking thrust faults, fault-related folds, and detachment folds. Two major decollement levels exist: an upper detachment in salt-gypsum lithologies in the Paleogene–Miocene Kumgeliem, Suweiyi, and Jidike formations, and the lower detachment mostly within Jurassic coal and mudstone strata. Fault-propagation folds developed above both detachments and have been refolded in some cases by displacement on the lower thrust faults. Imbricate thrust faults and duplex structures linking the two detachments developed with salt that apparently flowed into the cores of the duplex structure. Near the high Tianshan mountain front, Mesozoic and Cenozoic strata are involved in deformation that began at approximately 25–26 Ma as documented by growth strata north of Kuqa. Toward the southward limit of the fold belt, Miocene through Holocene strata are folded in the Quilitage and Yaken anticlines, which began growing above a thrust system that propagated at about 5.5 Ma. The Yaken anticline at the south edge of the eastern Kuqa fold belt has only emerged as a topographic anticline in the last 0.2–0.3 Ma associated with an acceleration of the Quilitage-Yaken thrust system.
Structural
restoration suggests a shortening of 15–20 km (9–12 mi) across the eastern Kuqa fold belt. Considering that this shortening began about 25 Ma, the average shortening rate was about 0.7 mm/yr (0.03 in./yr). Because the frontal thrust system underlying the Quilitage and Yaken anticlines has a shortening of 6 km (3.7 mi) that began approximately 5.5 Ma, their average shortening rate is about 1.1 mm/yr (0.04 in./yr). However, the shortening rate on this frontal system from about 5.5 Ma to about 0.2–0.3 Ma is approximately 0.6 mm/yr (0.02 in./yr) followed by an acceleration to about 4–5 mm/yr (0.16–0.19 in./yr) at approximately 0.2–0.3 Ma, causing the topographic emergence of these structures. These results indicate that shortening rates in the Kuqa fold belt have increased in the late Pleistocene, which is consistent with more regional present-day geodetic shortening rates of about 9 mm/yr (0.35 in./yr) across the southern Tianshan, which also indicate a substantial acceleration relative to Neogene shortening rates.
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