| 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. |