乌尔逊凹陷下白垩统高频层序特征及其控制因素分析

利用地质、地球物理等资料对乌尔逊凹陷下白垩统高频层序特征及其控制因素进行了分析。高频层序赋存于三级复合层序CSq7和CSq8内部,沿凹陷走向分布,总体以前积形态下超于复合密集段之上。层序边界属Ⅰ型性质,但不整合规模较小;层序内部包含3个体系域,准层序组总体呈加积-前积-退积-前积的叠加样式。研究区共识别出16个高频层序,平均周期为0.22~0.28Ma,沉积速率为0.57~0.76m/kyr。研究表明,低构造沉降速率和温暖潮湿气候条件下的高沉积物供给速率是控制高频层序发育的主要因素,三级基准面旋回高位稳定-缓慢下降阶段是高频层序发育的有利时期,盆缘地貌对高频层序几何学特征也有较大影响。

Analysis on Characteristics and Controls of High-Frequency Sequences of Lower Cretaceous Series in Wuerxun Depression

Based on the geological and geophysical data, this paper analyses characteristics and controls of high-frequency sequences of Lower Cretaceous Series in Wuerxun Depression. High-frequency sequences occur along the strike direction of the depression in third-order composite sequence 7 and 8, and show downlap of reflections onto the composite condensed section. Most of high-frequency sequences belong in type I, but the scopes of unconformities are very limited. There are three system tracts and parasequences stacking patterns from aggradation-progradation-retrogradation-progradation in high-frequency sequences. Sixteen high-frequency sequences are identified in this area. The average period and the sediment velocity of which is about 0.22 - 0.28 Ma and 0.57 - 0.76 m/kyr, respectively. This study suggests that high-frequency sequences have the greatest chance of forming under the conditions of low tec- tonic subsidence and high sediment supply during and that the marginal morphology of basin controls third-order base-level relative stabilizing and descending periods, the geometry of high-frequency sequences.