摘要
辽河、浑河、太子河、大凌河等河系从山区进入下辽河断陷盆地后,共同塑造了宽阔的下辽河平原;并在平原周边形成了一系列掩埋的第四纪冲积扇.本文就冲积扇形成的构造背景,扇体形态类型、扇体结构等进行了研究,对扇体沉积进一步划分为扇顶、扇中、扇缘亚相;通过对沉积物粒度分析、石英颗粒电镜扫描,表现了冲积扇碎屑沉积物的动力机制属于激流型强水动力条件所形成,具有供水意义.
River system such as Liaohe River, Hunhe River, Taizi River Daling River etc.enters into Lower Liaohc Graben Basin form moutains, modeling the vast Lower Liaohe Plain and forming a series of buri-cdQuaternary alluvial fans on periphery area of the plain which arc perfect resources of supplyiyg water for Shenyang, Anshan, Jinhou and othetr cities.
Lower Liaohe Plain is a rift basi in Middle Cenozoic. Since Quaternary neotectonic movement is inherited settle.The piedmont on periphery of the plain is strong place of tcctonization. So the structural slope belt on the piedmont is the premise condition which buried alluvial tan is formed.The plain area not only has huge terrihcnous clastic sediment (6000m-8000m) but also is the centre of Quaternary sediment in Liaoning province (more than 400m) .
Flowing out of mountain gaps, rivers form a series oflarge Quternary alluvial fans, there are Liaohe Fan, Hunhe Fan, Taizihe Fan, Dalinghe Fan. The area of only one fan is 1000to 1500 spuare kilometres, belong to large or middle-type.The shape and plane distribution of the fans are controlled by landform conditions which rivetrs flow out of mountain gaps.They usually distribute in the form of regular fan of tongue.The vertical shape of the alluvial fans is controlled by structure of basement.If the moutain gap has deep fracture or step fracture, the form of alluvial fans is sphenoid or step; if the mountain gap is sagged slowly, the form is lens. The lithofacies structure of the alluvial fans have obvious horizontal banding.The body of fans can be further divided into sedimentary subfacies of top, middle and edge of fans according to the lithological characters, thickness and its space position.The study on grain size of sediment and electron microscope scanning of quart grain shows that dynamic mechanism of coarse clastic sediment on the top of fans is strong hydrodynamism of rapids-type.The lithological characters of the top are gravel, grouan and sand which content is about 60-80 percent, the greatest thicknees is 100m, it is major place which water resources in city exploited recently.The edge of fan is clay which content is 60-90 pocrcnt.Water in it is very little, so it has no meanihg of supplying water.
These superposed alluvial fans formed from Late Middle Plcistoene of Late Pleistocene.
The vertical variations of grain size data of the fans body reflects thqt dynamic state and sedimentary environment change with time, φ values of grain in Late Middle and Late Pleistocene is more coarse than in middle.It shows that the climate was warm and the flow of river is large, it is the characters of flood period, identical with the climate characters rcpresntcd by data of sporo pollen and panning.
出处
《沉积学报》
CAS
CSCD
北大核心
1989年第3期63-72,共10页
Acta Sedimentologica Sinica
