查干凹陷下白垩统层序构型与沉积充填特征

The Sequence Configuration and Depositional Infilling Characteristics of Lower Cretaceous in Chagan Sag

查干凹陷下白垩统层序构型复杂多样,时空变化快,为研究该区层序构型特征,提出采用一种"A/B"分式表征层序构型的新方法。通过综合分析地质、钻测井和地震资料,下白垩统划分为2个构造层序、4个超层序、7个(三级)层序和17个体系域。在等时层序地层格架下,运用该方法研究各层序内部地层结构特征,下白垩统三级层序可划分为L/LTH型、T/LTH型、H/LTH型、TH/LTH型、L/LT型、T/LT型、LT型、T/TH型、H/TH型、TH型、T型、H型12种层序构型,及LTH型、TH型2种层序类型。进而详析各层序的层序构型类型与空间分布及体系域的沉积充填特征,揭示不同地质演化阶段层序构型特征有明显差异。

Researches show that the Lower Cretaceous sequence configuration of Chagan sag is complicated and multipie. and has a quick space-time change. A new method of adopting the fraction of A/B to characterize sequence configu- ration is put forward in order to more wholly and clearly reveal the internal architectural features of sequences in the re- gion.Through the comprehensive analysis of the geological, well-drilling, well-logging and seismic data, the Lower Cretaceous in Chagan sag is subdivided into two tectonic sequences, fbur super sequences, seven third-order sequences and seventeen system tracts, and the isochronous sequence stratigraphic framework of Lower Cretaceous is established. In the stratigraphic framework this method is used to study the stratum structure characteristics of every sequence, all the third-order sequences of Lower Cretaceous in Chagan sag are divided into twelve sequence configuration types in- cluding L/LTH type, T/LTH type. H/LTH type, TH/LTH type, L/LT type, T/LT type, LT type. T/TH type, tUTH type, TH type, T type, H type, and two sequence types including LTH type and TH type.On this basis the sequence configuration types and their spatial distribution, and the depositional infilling characteristics of system tracts of every sequence are analyzed in detail. It is indicated that different geological evolution stages have apparently different se- quence configuration characteristics.