| 广西南丹六寨马平组上段的深水碳酸盐岩屑流及其地质意义 |
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| 引用本文： | 江纳言
,周祖仁
,黄占兴.广西南丹六寨马平组上段的深水碳酸盐岩屑流及其地质意义[J].地层学杂志,1987(4). |
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| 作者姓名： | 江纳言 周祖仁 黄占兴 |
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| 摘 要： | <正> 以南盘江大断裂与南丹一河池大断裂为界,构成了西南侧晚古生代滇黔桂盆地和北东侧台区的分野。沿此界线的广西南丹、贵州罗甸、紫云和镇宁等地二叠纪地层中多处发现有不连续的层状砾屑灰岩体,被认为系一套包括滑塌和重力流堆积在内的台前斜坡相沉积。这些沉积物的颗粒组分主要由浅水碳酸盐岩屑和浅水生物屑所组成,具有异地碎屑流成因的颗粒特征(分选性差,不明显的或差的磨圆度,有或不明显的粒度递变现象和其他特征)。根据砾屑灰岩体的沉积构造特征和围岩及夹层的性质(深色、薄层状泥晶灰
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Deep-water carbonate debris-flow in the Upper Maping Formation of Liu-zhai, Nandan of Guangxi |
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| Abstract: | During late Paleozoic, Zhenning, Ziyun and Luodian of Guizhou and Nandan of Guangxi were situated in the same slope depositional zone, which approximately extended along the Nanpanjiang abyssal fault in the west and the Nandan-Hechi abyssal fault in the east. Paleogeographically, the Dian-Qian-Gui (Yunnan-Guizhou-Guangxi) Basin and the carbonate platform of South China were on its southwestern and northeastern sides. During the earliest Permian (Asselian) in this area the deep-water carbonate debris-flow was well developed, but discontinued in transverse extension. Several stratoid carbonate debris sheets of 0.2-6m thick are intercalated in the Asselian dark grey, thin-to medium-bedded micrites. They, as a high-density gravity flow, are generally characterized by their poor-sorted and poor-to moderate rounded and dominant shallow carbonate fragments or bioclasts and afford a striking contrast to underlying or overlying micrite beds. The clasts of the sheet range in size from granule to boulder-sized. Some of rectangular rock blocks are more than 10m in dimension. The fragments consist mainly of fossiliferous grainstone (biosparudite, biosparenites and so on) and fossil algae, brachiopods, ammonoids, bivalves, corals fusulinids, non-fusulinid foraminifers, ostracodes, bryozoans, echinoderms, trilobites, radiolarians, sponge spicules. etc. The source area of the material was considered to be situated in the carbonate platform northeast to the abyssal faults. In spite of the mixed fossil assemblages in the sheet, it was believed that the various fossils could be recognized as appraximately simultaneous in age, on account of that the debris-flow took place on the upper slope not far from the source area. Therefore, the carbonate debris-flow in this area is of vital importance to the environmental interpretation and biostratigraphic analysis. |
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