摘要
陕西榆林延安组湖滨下三角洲平原沉积中决口扇三角洲具如下特点:(1)发育在湖滨下三角洲平原的分流间地区;(2)平面上垂直主分流河道向外呈扇形或朵叶状;(3)剖面上呈透镜状夹在两个煤分层之间;(4)前三角洲沉积的厚度小,前缘中植物碎屑含量高;(5)发育时间短,一般不超过1万年。决口扇三角洲沉积体间的排列关系受控于压实沉降作用,不同的排列形式导致煤层出现叠瓦状分叉和环状分叉。
<ABSTRACT>
Yanan Formation, which makes up the major coal measures in the study area, is depos-
ited under large lacustrine deltaic environments which may be, to some extent, compared
with marine deltaic environments. The lacustrine delta deposits can be divided into the up-
per lacustrine delta plain deposits, the lower lacustrine delta pIain deposits and the
subaqueous lacustrine delta plain deposits. The splay deltas recognized in drillcores and out-
crops are one kind of the important component in the interdistributary area of the lower
lacustrine delta plain. Several sedimentary characteristics of the splay deltas summed up in
this study are as fo11ows: (1)The splay deltas are deposited in the interdistributary area of
the lower lacustrine delta plain; (2) The sandbodies of splay deltas are lobe--like or fan--like
in form; (3) In cross sections, the splay deltas take the lens--like shape between two coai
seams, (4) Thickness of the prodelta deposits is thin and there is abundant p1ant debris in
the splay delta front deposits; (5) Usually, the age, in which one of the splay deltas develops
continually, is less than 10000 years.
The relationship between splay delta bodies controlled by compaction and subsidence
shows as two types: imbrication and overriding. Respectively, the coal seam splits in two
forms: repeated split and ringed split. So the recognization of splay deltas in mining area
will benefit the correlation of coal and minimg production.
出处
《现代地质》
CAS
CSCD
1990年第3期51-59,T001,共10页
Geoscience
关键词
决口扇
三角洲
湖滨
下三角洲
平原
: splay delta, lower lacustrine delta plain, compaction and subsidence,Ordos basin
