| Based on such factors as boundary texture, extension, erosion and cessation of deposition,6 grades of sequence boundaries have been recognized in Xichang Basin,which include 3 mega order,4 super-order,3 Ⅰst order, 2 Ⅱnd order,7 Ⅲrd order,and 59 Ⅳth order boundaries.Different grades of sequences show different textures, characteristics and distributions. On such a basis in conjunction with tectonic and basin natures, basin-mountain transformation and sea-level change, 78 sequence boundaries in Xichang Basin can be grouped into 6 sorts of genetic types, namely, orogenic erosion, elevation erosion, subaerial erosion, exposed erosion, transgressive overlapping, and submarine cessation, of which each possesses its own formational background and mechanism. Furthermore, the relationship between the sequence boundary with strata division, basin evolution and petroleum reservoir has also been investigated in detail. It is revealed that the sequence boundary plays an important role not only in petroleum exploration but in the solution of such problems as strata surface and basin analysis as well. |