Salt tectonics in two convergent-margin basins of the Cyprus arc, Northeastern Mediterranean

Abstract

Seismic reflection profiles from the Adana–Cilicia and Iskenderun–Latakia Basin complexes in the NE Mediterranean Sea show the presence of linked extensional–contractional fault systems, detached at the base of the Messinian evaporites. The extensional domain is developed within the thick proximal part of the Plio-Quaternary delta succession in the inner part of each basin. It is characterized by imbricate fans of listric normal faults, which delineate turtle anticlines and their intervening syncline. The faults sole into the gently southwest-dipping detachment surface. In the inner basins, salt is largely evacuated toward the outer basins, but remnants occur as rollers in the footwalls of the listric extensional faults and small subdued pillows beneath turtle anticlines. The narrow synclines between the two turtle back growth anticlines record a more complicated history of rise and fall of the salt related to switch in vergence of the extensional fault fan. A large salt wall is developed at the toe of the delta complex in both basins. Two wide peripheral sinks are present within the Plio-Quaternary units on both flanks of the salt wall. Locally small segments of salt welds are present near the base of the salt wall. The contractional domain is characterized by a relatively thin Plio-Quaternary cover overlying a relatively uniform, 500–800 ms-thick salt substrate. A series of salt-cored growth folds are commonly associated with thrusts of variable vergence. The halokinetic structures in the Cilicia and Latakia Basins display a remarkable resemblance to detached and linked systems of extensional and contractional fault fans documented in classical salt provinces on passive margins. The study area also resembles scaled experiments which document synchronous development of extensional and contractional fault systems detached in a ductile substrate. However, a number of differences also exist, which may arise from several factors, including the nature of ductility contrast between the ductile portion of the evaporite layer and the supra-salt succession, the thickness ratio of overburden to evaporite unit, and the rate of progradation and the nature of sediment distribution during the evolution of the delta complex. The special aspect of these associations of linked gravity-driven extensional and contractional salt structures is that they are developed as a self-contained system wholly situated within a Plio-Quaternary transtensional basin.