广西来宾—合山一带晚二叠世海底扇浊积岩相  

LATE PERMIAN SUBMARINE FAN TURBIDITE FACIES IN THE LAIBIN-HESHAN AREA OF GUANGXI

作　　者：邵龙义[1] 张鹏飞[1] 

机构地区：[1]中国矿业大学,北京100083

出　　处：《古地理学报》1999年第1期20-31,共12页Journal of Palaeogeography：Chinese Edition

基　　金：国家自然科学基金(49772129)

摘　　要：广西来宾蓬莱滩及合山马滩两地的晚二叠世地层中发育有典型的重力流沉积构造,如粒序层理、包卷层理、槽模、重荷模、碟状构造和滑塌褶皱等。通过对蓬莱滩合山组和大隆组以及马滩剖面的大隆组岩相特征的详细研究,提出来宾蓬莱滩晚二叠世合山组和大隆组以及合山马滩晚二叠世大隆组形成于海底扇环境,划分出具碟状构造的块状砂岩(B_1)、块状砂岩(B_2)、近基浊积岩(C)、远基浊积岩(D)、不规则互层的砂泥岩(E)、滑塌褶皱层(F)及含浮游生物化石的页岩、硅质岩(G)等岩相类型,同时归纳出外扇相组合、中扇舌状体相组合、中扇水道相组合、斜坡相组合及深切谷水道相组合等,还对这些海底扇浊积岩系的古地理意义做了讨论。桂中碳酸盐岩台地相区和云开古陆之间在晚二叠世为一发育海底扇浊积岩的深水盆地,其中来宾—合山—带在大隆组沉积期处于水深约300～1000 m的深水盆地环境,合山—带火山活动提供的火山物质及来自东侧云开古陆的陆源物质构成该区浊积岩的主要物源。Late Permian submarine fan turbidites are well developed in the Laibin-Heshan area and are particu-larly well exposed in the Matan and Penglaitan sections along the Hongshui River. Varieties of sedimenta-ry structures formed by sedimentary gravity flow have been found in the field sections, such as graded beddings, flute casts, load casts, dish structures, and slump-folded layers. The lithofacies of Late Per-mian Heshan Formation and Dalong Formation in the Penglaitan section and Late Permian Dalong Forma-tion in the Matan section have been studied in detail. It is proposed that these formations were formed in a submarine fan. Lithofacies such as massive sandstones with dish structures ( B1 ), massive sandstones (B2) , proximal turbidites (C) , distal turbidites (D), irregularly interbedded sandstones and mudstones (E), slump-folded layers (F), and shales and siliceous rocks with planktons (G) have been recognized in the study area. The outer fan, mid fan lobe, mid fan channel, slope and incised valley facies associa-tions have been summarised. The palaeogeographic implications of these turbidites are also discussed. It is here considered that these turbidites were formed in deep marine environments between the Central Guangxi carbonate platform and the Yunkai Oldland, with an average water depth between 300 m and 1 000 m. Provenance in the Heshan area was volcanic, while the sediments in the Laibin area were mainly terrestrial and were derived from the Yunkai Oldland to the east.

关 键 词：海底扇 浊积岩相 晚二叠世 古地理背景 广西 重力流沉积 

分 类 号：P512.2[天文地球—地质学] P534.46