异重流沉积过程和沉积特征研究

异重流是一种与河口相连、密度大于周围水体(湖泊或海洋)沿水底流动的流体,通常在干热气候、少植被的地区洪水期产生,也是一种持续型浊流。综合资料表明,异重流在流动过程中流量振荡频繁,但整体表现为先增强、后衰减的特点。由异重流形成的沉积岩被称为异重岩,其识别标志包括其垂向上为复合韵律,交错层理和块状层理砂砾岩的交替出现,层面富含有机质和陆源植物碎屑以及内部冲刷面发育等。异重流沉积垂向叠加厚度达数十米,平面主要表现为以具有水道、舌状体和堤岸沉积单元的点物源富砂型或富泥型海(湖)底扇为特征。由于异重岩具备形成优质储层的良好条件,因而具有重要的油气地质意义,可以作为有利的勘探目标。

Research on Sedimentary Process and Characteristics of Hyperpycnal Flows

Hyperpycnal flow, one of the most significant sediment delivery systems to deep water, has aroused a great concern for a considerable number of marine geologists and sedimentologists in recent years. It is a kind of subaquatic flows which have higher density than the ambient water (lakes or oceans) discharging from river mouth, and usually occurs during the flooding period of some areas that lack of vegetation under extreme dry and hot climate. Hyperpycnal flows are sustained turbidity currents, containing bed-loads and suspended-loads to transport sediments. They could vibrate frequently during the flowing process, but mainly wax initially and wane later. Hyperpycnites are hyperpycnal flows deposits. The remarkable recognitions of hyperpycnites include vertical composite rhythm, repetitive alternation of cross bedding and massive layers, organic matters, a large amount of plant debris and internal scouring surfaces. The thickness of stacking ancient hyperpycnites vertically could be more than ten meters, and they also behave as a point-source sand-rich or mud-rich submarine (sublacustrine) fan with channels, levees and lobes laterally. Hyperpycnites could play crucial role in oil and gas geological merits and economic values because of extraordinary conditions to be high quality reservoirs and could be rather promising exploring targets.