Quaternary activity of the range front thrust system in the Longmen Shan piedmont, China, revealed by seismic imaging and growth strata

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• 作者：Zhigang Li ; Jing Liu‐Zeng ; Dong Jia ; Chuang Sun ; Wei Wang ; Zhaode Yuan ; Baojin Liu
• 刊名：Tectonics
• 出版年：2016
• 出版时间：December 2016
• 年：2016
• 卷：35
• 期：12
• 页码：2807-2827
• 全文大小：3.8MB
• ISSN：1944-9194

文摘

Reliable estimates of Quaternary or Cenozoic upper crustal shortening in the Longmen Shan fold-and-thrust belt are rare. In this paper, we report on our use of high-resolution 2-D and 3-D seismic reflection profiles at various scales, together with borehole data, to investigate the structural geometry of the Longmen Shan piedmont. The results reveal a thrust system beneath the Longmen Shan, termed the range front thrust system, which consists of the range front blind thrust and its upward splay faults. Moreover, on these faults we identified growth strata that provide an excellent opportunity for assessing the activity of this thrust system. Analyses of the growth strata reveal early to late Pleistocene activity on the range front blind thrust, with minimum dip slip and horizontal shortening rates of 1.1 ± 0.2 mm/yr and ~1 mm/yr. Accordingly, the maximum accumulated slip on the range front blind thrust is calculated to be 7.5 ± 0.3 km in the Longmen Shan. Using the new horizontal shortening rate and other published data, we also estimated that the long-term shortening rate across the Longmen Shan fold-and-thrust belt is 1–3 mm/yr, which is comparable to the short-term GPS rate. The similarity of these rates suggests that the Longmen Shan attained a steady state condition over the past 2 Myr. An additional highlight of our results is that we show Quaternary activity around the Tibetan Plateau to have been nearly synchronous in different regions, including in the Longmen Shan, the Himalayas, the western Kunlun Shan, and the northern Qilian Shan.