摘要
古构造、古气候和古基准面控制着盆地活动性质、供源体系和沉积物粒度等，从而控制着三角洲前缘砂体的类型及分布。通过全盆地123口井的岩心（共4600m）、26条露头和1078口单井的系统分析，发现四川盆地上三叠统三角洲相砂体可细分为扇三角洲砂体、辫状河三角洲砂体和曲流河三角洲砂体3类。古构造、古气候和古基准面控制三角洲前缘砂体类型。古构造包括盆地古地形、盆地结构和构造活动特征。平坦古地形造成滨岸带宽度和底形摩擦力增大，从而滨岸带水体能量降低，三角洲前缘河道砂体发育。盆地结构控制着物源供给、地形坡降和水流性质，从而控制三角洲前缘砂体类型和分布。幕式运动造成构造平静期和活跃期交替，物源性质和地形坡降也随之改变，使三角洲前缘不同砂体交互出现。古气候变化造成季风性质和植被性质差异，季风盛行的干燥时期水体能量高，三角洲前缘水下分支河道砂体改造强烈，滩坝砂体大面积发育；季风不盛行的潮湿期水体能量低，物源供给较小，三角洲前缘砂体易于保存，河道砂体发育。基准面下降期，盆地水体收缩，三角洲砂体向盆地推进，河道砂体发育；基准面上升期，盆地水体改造能力强，三角洲前缘滩坝砂体发育。
Paleotectonics, paleoclimate and base level fluctuation control the attribute of basin activity, provenance system and sediment grain size, and thus determining the type anddistribution of delta and beach bar sand body. Based on the systematic analysis of cores from 123 wells （total length of 4 600 m ）, 26 outcrops and logging data of 1 078 wells, we found that delta sand body were developed in the 1st, 3rd and 5th Member of the Upper Triassic Xujiahe Formation, and beach bar sand body were developed in the 2nd, 4th and 6th Member of Xujiahe Formation. Delta sand body can be subdivided into fan delta, braided river delta and meandering river delta sand body; beach bar sand body can be subdivided into reverse graded and normal graded sand body. Paleotectonics, paleoclimate and base level fluctuation control the type and distribution of delta and beach bar sand body. Flat paleotopography results in the increase of seaboard width and bed form friction, due to which the seaboard water energy is low and the delta sand body is easily preserved. Basin structure controls the provenance supply, topographical gradient and flow properties, thereby determining the type and distribution of delta sand body. Episodic movement causes the alternation of tectonic quiet period and active period, thus the change of provenance properties and topographical gradient, resulting in the alternation of delta and beach bar sand body. Paleoclimate change leads to the variation of monsoon properties and vegetation： Water energy is high, delta sand body is strongly reformed and beach bar sand body is developed in a large area during the dry monsoon period; water energy is low, provenance supply is low and delta sand body is easily preserved during the mild non-monsoon period. When the base level descends, basin water covers a smaller area and delta sand body advances toward the basin ; when the base level ascends, basin water has a stronger reforming capacity and the beach bar sand body is well developed.
出处
《地质科学》
CAS
CSCD
北大核心
2017年第1期270-284,共15页
Chinese Journal of Geology(Scientia Geologica Sinica)
基金
国家自然科学基金项目“晚三叠世四川盆地不同类型三角洲内部构型及成因模式”（编号：41572079）资助.
关键词
三角洲
滩坝
古构造
古气候
基准面
上三叠统
四川盆地
Triassic
SichuanDeltaBasin
Beach bar
Paleotectonics
Paleoclimate
Base level
Upper
