陆相断陷湖盆异重流与滑塌型重力流沉积辨别

异重流和滑塌型重力流是依据沉积物供给条件划分的2种重力流类型，代表了近年来重力流沉积学研究的新进展，但在实际应用中还存在概念混淆和沉积物识别的不确定性问题。基于渤海湾盆地黄骅坳陷歧口凹陷的钻井岩心、测井和砂岩粒度分析资料，对比分析异重流和滑塌型重力流沉积在岩石学、沉积构造和粒度分布特征上的差异和识别标志，研究结果表明，二者在陆相断陷湖盆中的有利发育场所为断控陡坡带扇三角洲前、断阶带辫状河三角洲前和具挠曲坡折的缓坡带三角洲前。异重流沉积突出表现为发育砂基支撑的砂砾岩，砾石磨圆度好，发育粗尾正递变层理或逆递变层理，粒度分布直方图呈双峰式，累积概率曲线呈二级台阶式。相比之下，滑塌型重力流沉积突出表现为分选较好，发育含较多泥岩碎块（撕裂屑）的块状砂岩，具有滑塌构造、液化变形构造和包卷层理，粒度分布直方图呈正态单峰式，累积概率曲线呈上拱式。异重流和滑塌型重力流沉积的差异在于沉积物供给条件和重力流流态的不同。异重流受洪水流物源供给，具有高含水量、低密度和低黏度的特征，主要表现为浊流流态；滑塌型重力流受控于滑塌作用和二次沉积机制，具有低含水量、高密度的特征，主要表现为砂质碎屑流流态。

Differentiation between hyperpycnal flow deposition and slump-induced gravity flow deposition in terrestrial rifted lacustrine basin

Two types of gravity flow, i.e., hyperpycnal flow and slump-induced gravity flow, are divided according to the sediment supply conditions, representing the new progress in research on gravity flow sedimentology in recent years. However, there are still conceptual confusions and uncertain identifications of sediments in practical applications. Based on the data of drilling core, logging and sandstone grain size from Qikou sag, Huanghua depression, Bohai Bay Basin, a comparative analysis is performed on the differences and the identification marks of depositions between hyperpycnal flow and slump-induced gravity flow in petrology, sedimentary structure and characteristics of grain size distribution. Studies show that the favorable development sites for these two types of gravity flow in terrestrial rifted lacustrine basin are the fan delta front at fault-controlled steep slope zone, braided river-delta front at fault terrace zone, and delta front at the gentle slope zone with bending slope break. The hyperpycnal flow deposition is characterized by the development of sandy conglomerate with good psephicity of gravels, developing coarse-tail normal graded bedding or reverse graded bedding, and showing bimodal and stepwise cumulative probability distribution in grain size analysis. In contrast, the slump-induced gravity flow deposition is characterized by good sorting massive sandstones, containing plenty of mudstone fragments (ripped-up mud clasts), developing slump structure, liquefaction structure and convolute bedding, and showing normal unimodal and convex cumulative probability distribution in grain size analysis. The difference between hyperpycnal flow and slump-induced gravity flow lies in the variations of sediment supply conditions and gravity flow patterns. Fed by the flood flow, the hyperpycnal flow is mainly turbidity flow in flow pattern, with the characteristics of high water content, low density and low viscosity. Controlled by the mechanism of slumping process and secondary deposition, the slump-induced gravity flow is mainly sandy debris flow in flow pattern, with the characteristics of low water content and high density.