济阳坳陷古近系区域层序地层格架地层特征对比

Correlation of stratigraphic features in regional sequence stratigraphic framework of the Paleogene in Jiyang Depression

综合生物地层学、磁性地层学(ESR测年法)、地震地层学及层序地层学等地层学的研究成果,通过对断陷盆地区域等时界面的识别、界面级次和界面性质的分析与对比,以三级层序为基本组构单元建立了济阳坳陷古近系区域层序地层格架系统。通过分析济阳坳陷4大次级凹陷古近系各二级层序和隐蔽油气藏最为发育的重点三级层序的可对比性,认为二级层序完全受构造幕的直接控制,具有很好的可对比性。4个次级凹陷的重点三级层序的旋回性质具有一致性,标志性沉积物出现于相同或类似的旋回位置。然而,T2(沙一段底)、T4 (沙三段上亚段底)和T6(沙三段中亚段底)三级层序界面的性质在不同凹陷问具有明显的差异性。从层序成因动力学角度来解释,这种旋回性质的相似性和界面性质的差异性分别表明了:同一层序地层格架中沉积环境对沉积物类型起决定性的影响作用,以及渤海湾盆地构造沉降、沉积中心的迁移对层序界面性质具有主要的控制作用。

According to the comprehensive research achievements of stratigraphy such as biostratigraphy, magnetostratigraphy （ESR dating method ）, seismic stratigraphy and sequence stratig raphy and by means of the recognition of regional isochronous sequence boundaries, the analysis on boundary orders and the correlation of boundary properties in the faulted basin, a regional sequence stratigraphic framework of the Paleogene in Jiyang Depression is established on the basic unit of thirdorder sequences. Then the analysis on the comparison of all second-order sequences and major third-order sequences in which subtle reservoirs were developed, shows that the second-order sequences are directly controlled by tectonic episodes in the four sub-sags of the Jiyang Depression, therefore, they are similar in characteristics. The cyclicity of major third-order sequence stratigraphic framework coincides with each other among the four sub-sags, with the marker sediments developed in the same or similar cycle positions. However, the third-order sequence boundary properties of T2, T4, and T6 are apparently different among different sub-sags. According to the sequence genesis dynamics, the consistency of cycle properties and the difference of boundary properties respectively indicate that the sedimentary environments control the sediment types in the same sequence stratigraphic framework and the migration of tectonic depocenters and sedimentary centers in the Bohai Bay Basin controls the sequence boundary properties.