3D seismic analysis of circular evaporite dissolution structures, Eastern Mediterranean

摘要

Buried circular collapse structures above a tabular evaporitic body are recorded by recently acquired 3D seismic data on the Levant Basin and continental margin, offshore Israel (Eastern Mediterranean). The structures formed during the Pliocene as buried Messinian (late Miocene) evaporites underwent extensive dissolution in a submarine, deep-water setting. Three-dimensional seismic analysis is used to describe the detailed morphology of the structures and the associated overburden, allowing the reconstruction of their origin and development. It is proposed that evaporite dissolution led to the collapse of the weakly lithified overburden, and this deformed with a series of concentric extensional faults. From the structural analysis of the overburden, the estimated maximum duration of the dissolution event is 0.75–1 Ma. The mechanism proposed for the creation of the circular collapse structures is subjacent dissolution of the more soluble evaporites in the Messinian evaporites, as a result of focused vertical fluid flow at the base of the evaporitic series. Rapid release of overpressured fluids, as, for example, during an earthquake, is thought to have initiated the focused fluid flow, which impinged on the evaporitic seal to the point where dissolution occurred, creating the localized circular collapse structures in the overburden.