摘要:
四川盆地中西部(图1)上三叠统(即原“香溪群”)几个主要砂层的沉积环境,经与许多古今沉积对比,发现它们与现代河口地区的水(海)进河床充填砂体(简称水进河床砂体或水进河床沉积,下同)颇为相似,于是将其定为此种微相类型。所谓水进河床充填砂体,是水进期间沉积物填充河湖(或海)交汇地带的河道所形成。这种沉积体,近年来先后在我国长江口、珠江口、滦河口的现代沉积中被发现。据报导,非洲的尼日尔,美国的密西西比与拉瓦卡等河的河口附近亦有此类砂体存在。从许多古代沉积的实际资料看,在河湖(海)交汇地带,水进期的河道充填砂体更常见。
Abstract:
Certaiin Upper Triassic sand-bodies in the middl一western Part of the Sichuan Basin possess the pasitive Grain-si rhythm with urdcrlying strata of terrestr-ial facics and ovcrlying strata of lacustrine facies. Their bedding is underdevel-oped and scouring unclear.They contain glauconite and have a grain-size prob-ability curve of three-section type, which reflects bidirectional flow ression cauce filling and conta-ins bisaltational components, quite similar to the peculiarities of the water-transgression cauce filling sand-bodies in recent stream-mouth regions. Theref-ore,they can be classified as this kind of sedimentation.They are sediments fi-lling cauce during the water-transgrained sediments formed at the intervals above the stream-mouth while the water surface of the basin was rising gradually, and the stream-mouth was retrogressing upstream.They have certain similarities and some obvious differences as compared with the river course sand-bodies and delta front stream-mouth bar sand-bodies. The mechanism is quite different, and so it is nccessary to differentiate them from each other.
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