基底倾斜对冲断变形的控制作用——以龙门山冲断带为例
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1.中国石油大学北京地球科学学院;2.山东农业大学 资源与环境学院;3.中国石化胜利油田分公司物探研究院;4.山东石油化工学院;5.中国石化胜利油田分公司;6.中国石化胜利油田分公司勘探开发研究院

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国家自然科学基金项目(面上项目,重点项目,重大项目)


The basement dipping’s control on the structural deformation of the Longmenshan thrust belt
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1.College of Geosciences, China University of Petroleum (Beijing);2.College of Resources and Environment, Shandong Agriculture University;3.Geophysical Research Institute of Shengli Oilfield, SINOPEC;4.Shandong Institute of Petroleum and Chemical Technology;5.Shengli Oilfield Company;6.Exploration and Development Research Institute,Shengli Oilfield Company,SINOPEC

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    摘要:

    基底倾斜是控制冲断带构造变形的重要因素。目前,学者对龙门山冲断带基底倾斜变形的研究较为薄弱。本文解译地震剖面发现,龙门山冲断带北、中、南段的基底变形亦具有差异性:北段整体向前陆倾斜2.6°,形成于冲断席的隆升作用;中段向后陆倾斜3.2°,形成于多期前陆压陷作用;南段向后陆倾斜2.6°,形成于早期伸展断陷和后期前陆压陷作用;新近纪以来,中、南段的后陆基底在青藏高原隆升作用下显著隆升。数值模拟实验表明,基底向后陆倾斜、水平沉降均会抑制构造变形向前陆扩展、产生冲断席叠加,而基底先存倾角的控制作用则反之;基底保持水平或向前陆倾斜时,后陆冲断席的隆升作用强于前陆,会造成基底整体向前陆倾斜;基底向后陆倾斜、浅表沉积时,楔形地层会促进斜坡带发育反向冲断。结合低温热年代学证据,数值模拟验证了龙门山冲断带南段基底的构造演化:晚白垩世以前,南段发育伸展断陷,沉积西厚东薄地层,基底向西倾斜;晚白垩世—始新世,南段发育前陆盆地,基底向后陆倾斜沉降;渐新世—中新世,南段的冲断变形向盆内强烈传递,基底基本无沉降;上新世以来,南段的后陆基底在青藏高原隆升作用下隆升,形成现今陡变地形。

    Abstract:

    The basement dipping is an important factor controlling the structural deformation of thrust belts. However, rare attentions have been paid on the basement dipping characteristics of the Longmenshan thrust belt. Based on interpretations of seismic profiles, this paper found that the Longmenshan thrust belt in the northern, central and southern segments underwent different basement dipping. The basement dipped 2.6° toward foreland in the northern because of the uplift of thrust sheets. The basement dipped 3.2° toward hinterland in the central due to several phases of loading. The basement dipped 2.6° toward hinterland in the southern which was the result of earlier rifting and later loading. The numerical experiment shows that the basement dipping toward hinterland or horizontal subsiding will suppress the forward propagation of thrusting deformation, and superimposed the thrusting sheets. While the control effect of the pre-existing basement dip is opposite. When the basement remains horizontal or dip toward the foreland, the thrust sheets in hinterland uplifted stronger than that of the foreland, which will cause the basement dipping toward the foreland as a whole. When the basement dipped backward with syn-sedimentation will result in the back-thrusting in slope zone. Numerical simulation proved the basement evolution in southern segment of the Longmenshan thrust belt. Before the Late Cretaceous, it was in an extensional regime with thick strata in the west and thin strata in the east, and its basement dipped to the west. During the Late Cretaceous—Eocene, a foreland basin developed, and the basement dipped toward hinterland because of the loading. During the Oligocene—Miocene, the thrusting deformation strongly propagated into the basin, and the basement almost had no dipping. Since the Pliocene, the basement in hinterland has been uplifted because of the Qinghai-Tibet Plateau, which resulted in the sharp topography.

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  • 收稿日期:2023-12-01
  • 最后修改日期:2024-01-07
  • 录用日期:2024-02-25
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