Late-Quaternary Folding of the Mingyaole Anticline Southwestern Tip, Pamir-Tianshan Convergent Zone
详细信息
- 责任者：Li Tao (State Key Laboratory of Earthquake Dynamics ; Institute of Geology ; China Earthquake Administration ; Beijing 100029 ; China) ; Chen Jie
- 刊名：Seismology and Geology
- 出版年：2013
- 卷期：35(2)
- 关键词：背斜 ; anticlines ; 褶皱 ; folds ; 天山 ; Tianshan Mountains ; 帕米尔高原 ; Pamirs
- 页码：p.234-246
- 图表：illus., 2 tables, 30 refs.
- 分类号：0300
- issnNo：ISSN0253-4967
- isbnNo：CN11-2192/P
摘要
Folding growth in three dimensions involves shortening in transversal direction,uplift in vertical direction and lateral propagation in longitudinal direction. The impact of these three components changes along the fold’s strike: the middle part is dominated by shortening and uplift,and deformation neighboring the fold tip involves not only shortening and uplift,but also strong lateral propagation. Previous studies are focused on the middle part,and the fold tip,a relatively special part,however,is poorly investigated. Thereby,how does the fold tip grow,what is the deformation difference between fold tip and the middle part,and how do terraces deform in response to folding growth? Our study to the southwestern tip of the Mingyaole anticline,located at the Pamir-Tianshan convergent zone,indicates terrace surfaces are strongly back-tilted,and display increasing dips with age,implying a limb rotation mechanism. According to the OSL ages of the T2b ,T3b and T4a ,a s well as a magnetostratigraphy age of underlying bedrock,rotation angle increments of the dip domain 46° display a parabola tendency with the age of < ～ 0. 35Ma,( 93. 9 ± 18. 7) ka,( 82. 6 ± 16. 5) ka and ( 19. 4 ± 2. 9 ) ka,and the average rotation rate is > ( 0. 13 ± 0. 01 ) ° /ka,( 0. 08 ± 0. 02 ) ° /ka, ( 0. 05 ± 0. 01) ° /ka and ( 0. 04 ± 0. 01) ° /ka,which display an obviously decreasing tendency too. However,the shortening rate absorbed by this dip domain keeps constant. The fluvial terraces display not only tilted and uplifted in response to the shortening and uplift of the fold,but deformed in response to lateral propagation. Toward west,density,width and depth of gullies on the terraces decrease,and elevation to the riverbed of the terrace surface,height of the terrace riser as well as rotation angles of terrace surfaces display a decreasing tendency too,both of which are consistent with the fold’s western-ward propagation. Based on the magnetostratigraphy age of ～ 1. 6Ma at the Kapake valley section,the average western-ward lengthening rate is about 16 ～ 16. 8mm/a.
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