陆相坳陷型和断陷型湖盆层序地层样式探讨

依据层序地层学基本理论,考虑中国中新生代陆相坳陷型和断陷型湖盆的盆地结构和沉积物充填序列特征,综合利用地质和地球物理资料,以松辽盆地白垩系和准噶尔盆地侏罗系、柴达木盆地第四系和渤海湾盆地第三系为研究实例,将坳陷型湖盆沉积层序细分成可以确定首次湖泛面和不能确定首次湖泛面的两种类型,建立了这两种类型湖盆的层序地层样式。前者由低位、湖侵和高位体系域组成,后者由湖侵和湖退体系域构成。在断陷型湖盆中,可将盆地缓坡由同生断裂活动造成的地势变化带作为地形坡折带(构造坡折带)并用于确定首次湖泛面,进而讨论了首次湖泛面和最大湖泛面的多种识别标志,建立了由低位、湖侵和高位体系域构成的断陷型湖盆层序地层样式。

Sequence Stratigraphic Models of Depression and Faulted-down Lake Basins

Under the guidance of theory of sequence stratigraphy originated from the study of marine basins in continental margin, this paper analyzed thoroughly the characteristics of basin texture and sediment filling sequence in Chinese Mesozoic-Cenozoic depression and faulted down lake basins, used the geological and geophysical data,took the Junggar ,Qaidam , Shongliao and Bohaibay basins as the cases for studying sequence stratigraphy, and pointed out the key of continental sequence stratigraphy study is to determine sequence boundary, first and maximum lake flooding surfaces. It does show that topographic break may be recognized in some depression and faulted down lacustrine basins. Therefore, the sequence stratigraphic models have been built in depression lake basin with or without topographic break. One sequence in depression lake basin with topographic break is composed of lowstand, transgressive and highstand systems tracts, but the sequence in depression lake basin without topographic break only is made up of transgressive and regressive systems tracts. In faulted down lake basin, there are some growth faults in gentle slope of a basin, the different activity of the growth fault produced a topographic change and formed a topographic break, so the sequence stratigraphic model of faulted down lake basin with topographic break has been built, which consists of lowstand, trangressive and highstand systems tracts .Also, this paper has discussed how to determine first and maximum flooding surfaces and sequence boundary according to geological, well-logging and seismic data.