川东北类前陆盆地须家河组盆-山耦合过程的沉积-层序特征  

Depositional Sequence Features during Coupling Process Between Basin and Mountain of the Xujiahe Formation of Upper Triassic in the Foreland Basin,NE Sichuan

作　　者：郑荣才[1] 朱如凯[2] 戴朝成[1] 高红灿[1] 翟文亮[1] 

机构地区：[1]成都理工大学'油气藏地质及开发工程'国家重点实验室,成都610059 [2]中国石油勘探开发研究院油气储层重点实验室,北京100083

出　　处：《地质学报》2008年第8期1077-1087,共11页Acta Geologica Sinica

基　　金：中国石油天然气总公司攻关项目“前陆盆地油气成藏与富集规律研究”(编号06-01A-02-01)资助成果

摘　　要：根据层序界面识别和沉积序列综合分析,将川东北地区须家河组划分为2个超长期和5个长期基准面旋回层序。此二个级别的层序结构和演化序列,较为清晰地反映了川东北前陆盆地晚三叠世须家河期盆-山耦合过程,特点为:须二段—须三段"下成盆"期米仓山-大巴山造山带以低幅隆升为主,对应的川东北坳陷沉降幅度小,物源供给与可容纳空间增长率稳定和基本持平,以发育辫状河三角洲-湖泊沉积体系为主,其层序结构以上升与下降相域厚度近于相等的对称型为主,反映地层基准面相对稳定和均衡的盆-山耦合过程;须四段—须六段"上成盆"期米仓山-大巴山开始进入强烈逆冲推覆和构造隆升阶段,川东北前陆盆地坳陷幅度急剧加大,碎屑物供给量骤然和增多至远大于可容纳空间增长率,以发育冲积扇-扇三角洲-辫状河三角洲等粗碎屑岩为主的沉积体系为主,其层序结构以上升相域厚度大于下降相域的不完全对称型,在造山带前缘则以发育仅保留上升半旋回沉积记录的非对称型结构为主,反映地层基准面升、降变化大的非均衡盆-山耦合过程。Using the multifactorial analysis of identification of boundary sequence and depositional sequences, the Xujiahe Formation in NE Sichuan can be divided into two extremely long and five long base-level cycle sequences. The sequence structure and evolution of both sequences have clearly reflected the coupling process between basin and mountain of the Xujiahe Formation of Upper Triassic in the northeastern Sichuan foreland basin. It is characterized mainly by low-amplitude uprising of the Mingcanshan-Daban orogenic belt during the lower basin-forming period of T3x^2-Tax^3 member, and by low-amplitude subsiding of the northeast depression. Material supply was basically balanced with the low amplitude of accommodating space. Braided river delta - lake sedimentary system was main system developed, and its sequence is characterized by that the thickess of rising equals to that of subsiding, reflecting a relatively stable coupling of basin and mountain. During the upper basin-forming period of T3x^4-T3x^6 members, the Micangshan-Dabashan Mountains entered an stage of intensive thrusting-napping and uplifting, resulting in a sudden, rapid subsidence of the foreland basin in NE Siehuan. Clastic sediments increased so dramatically that accommodation space was unable to store. Therefore, alluvial fan-fan delta braided river delta sedimentary system developed, with uplifting thickness more than that of subsiding. The rising cycle of base-level sedimentary sequence, retained in the front of orogenic belt, is asymmetric, reflecting a great imbalanced coupling process of basin and mountain with the base-level sequence uplifting and subsiding.

关 键 词：川东北 上三叠统须家河组 前陆盆地 盆-山耦合 基准面旋回 沉积序列 层序-岩相古地理 

分 类 号：P618.13[天文地球—矿床学]