前陆盆地层序地层学研究中的几个问题

Sequence Stratigraphy Discussions for Research Foreland Basins

用层序地层学理论和工作方法来研究聚敛型活动大陆边缘的前陆盆地沉积地层时应力求使用术语上的统一，使用一级（旋回）层序、二级（旋回）层序、三级（旋回）层序等，每一级别的（旋回）层序可以划分低水位体系域、海（水）进体系域及高水位体系域、海（洪）泛面等。层序级别的划分以持续的时限为标准。各级别的层序界面以不整合面或沉积间断面或与之相应的整合面为标志。前陆盆地可容空间的变化主要受控于构造作用和全球海平面变化（假定物源供给稳定）。在造山构造活跃期，前陆挠曲作用占主导地位；在构造期后（构造宁静期），全球海平面变化主要控制可容空间。这两种因素都以不同内容和形式在沉积层序中得到响应。通过详细的岩石学、沉积学、地层学以及各沉积区（前陆盆地即前渊、前隆和隆后盆地）剖面的区域对比研究，并与“标准”的全球海平面变化曲线图进行对比，可以区分出二者对前陆盆地形成、发育、演化的不同影响。

Used sequence stratigraphy to study foreland basin depositional sequences,we should try our best to get the terminology uniform. It is the best choice to use first_order (cyclic) sequences,second_order (cyclic) sequences,third_order (cyclic) sequences,etc..And various orders may be divided into lowstand system tracts (LST),transgressive system tract (TST),highstand system tract (HST),flooding surface and so on.The durations of sequences can be regarded as a criteria to determine hierarchies of sequences.The sequence surfaces of various orders are usually bounded by hiatuses or unconformity surfaces or related conformity surfaces. The accommondation spaces of foreland basins are mainly controlled by tectonism and eustacy (Assumedly supply rates are stable).When tectonic movements,the tectonism is in the first position for formations of foreland basin depositional sequences,vice versa,the eustacy in the first position.These two factors are recorded in strata in different signatures and contents.We usually can recognize them through detailed research of petrology,sedimentology,stratigraphy,regional section correlations of the sedimentary areas (foreland basins,forebulges and back-bulge basins),and correlation with “standarded” eustatic curves.