Moreover , the system tracts in sequence are characterized by dualistic structure , namely transgressive - highstand system tracts , and tst > hst . the parasequences are divided into three types , which is respectively dominated by sandstones , mudstones , and shallowing - upward tidal flat system . and prograding sequence and retrograding sequence are composed of stacking parasequence set 層序中體系域具有二元結(jié)構(gòu)特征,即海侵?高水位體系域,且tst hst ,準(zhǔn)層序類型有三種,分別是以砂巖為主的準(zhǔn)層序、以泥巖為主的準(zhǔn)層序和以潮坪體系向上變淺的準(zhǔn)層序。