河流相地层相分异与沉积物体积分配规律

Facies differentiation and sedimentation volume partition of fluvial strata

李宏伟 袁士义 朱怡翔 田昌炳 范军侠 闫林

Li Hongwei Yuan Shiyi Zhu Yixiang Tian Changbing Fan Junxia Yan Lin

基准面升降伴随着可容纳空间的变化,导致沉积物在不同相域发生剥蚀、搬运、过路、沉积或欠补偿作用而形成旋回性沉积地层。陆相地层等时对比中的同期不等厚现象是相分异与沉积物体积分配作用的地层响应。在平行物源的方向上,岩相类型可以由辨状河相序向曲流河相序以及三角洲相序迁移;而在垂直物源的方向上,岩相类型可以由河流相的河道充填沉积向河道间的溢岸沉积与漫滩沉积变迁,或者由三角洲相的分流河道沉积相变为分流间湾沉积。相分异过程伴随着沉积物的体积分配,使同一时期发育的地层在不同相域内分配的体积不同。古地貌对河流相产层分布具控制作用。古水流的搬运作用形成沿层序界面之上可容纳空间较大的古地貌低势区展市的各地充填河道砂体。

Elevation and subsidence of base level,accompanying change of accommodation space,leading to denudation,transportation,passing by,sedimentation or undercompensation of sediments in various facies tracts,would result in cyclic sequences.The phenomena of synchronic formations having different thicknesses seen in isochronal correlation of terrestrial formations are the stratigraphic responses to facies differentiation and sedimentation volume partition.In the direction parallel with sources,lithofacies types might change from braided channel facies sequence to meandering stream and delta facies sequences;while in the direction perpendicular to the sources,the fluvial facies might change from channel fill to interchannel washover and flood plain deposits,or the delta facies might change from distributary channel deposit to inter-distributary bay deposit.Facies differentiation accompanied by sedimentation volume partition would result in different volume partitions of synchronous deposit in different facies traets.Palaeogeomorphology might have controlled the distribution of fluvial facies reservoirs.Transportation of palaeocurrent might lead to the deposition of channel sandbodies on the sequence boundary where valleys have been developed in the palaeogeomorphologic low-land with relatively large accommodation space.

10.11743/ogg20050315