The Relationship between Sea Level Change and Cave Formation Sequence

Sequence stratigraphy provided a theory and significant tool for the global or regional stratigraphic isochronous correlation, it was also suitable for karst events analysis and regional correlation of caves related to sea level changes. The main topic for this paper is to discover the fundamentals in the intersecting domain between paleokarst and sequence stratigraphy through the study of the relationship between the sea level change and the cave formation sequence followed by the principle of the water table changed with sea level and the cave formation was only developed in the period of standing sea level. By the study of Yate (in U.S.A.) and Tahe (in Tarim basin) oil field, outcrop of Emei Mountain, as well as the integrated analysis of previous study, 3 general models about the relationship between the sea level change and the cave formation sequence are provided including that one is for the multiple karst island lenses corresponding to sedimentary cycles within the sequence-stratigraphic framework in which developed a normal succession of cave formation (the upper the younger, the lower the older); and the other two are for paleokarst in the continent carbonate blocks, in which it could develop the normal or reversed cave formation sequence followed by sea level intermissive rising or dropping. With the direct or indirect evidences, such as the started outcropping time of carbonate blocks, paleokarst environments and other geological conditions, the characteristics of karst and the deposits in the horizontal caves, indicating that the great cave system in the residue of Ordovician of Tahe oil field were developed in a sea level intermissive rising half cycle of 2-order sequence. The isochronous relationship of depositional sequence and cave can be applied in dating the paleokarst events, predicating the possible depth of caves; it has significant value in minerals exploration and engineering geology.