RISE, CLOSURE AND REACTIVATION OF THE BICORB-QUESA EVAPORITE DIAPIR, EASTERN PREBETICS, SPAIN

The Bicorb-Quesa diapir belongs to a complex system of evaporite diapi rs located in the SE Iberian Peninsula. It was emplaced along the axis of a graben system flanked by two syn-diapir growth basins filled by Miocene sediments. The Miocene evolution of the diapir may be divided into three major phases: an initial extensional phase during which the graben system formed and the diapir rose; a second phase during which regional shortening closed the diapir; and a third phase characterize d by normal faulting during which diapirism was reactivated, cutting t he previously-formed thrusts and folds. This evolutionary trend demons trates that diapirism was initiated and promoted by regional extension . During the two extensional phases, the diapir grew by reactive, acti ve and passive rise. Sedimentation during the reactive stage was chara cterized by strong basin subsidence, sharp changes in sediment thickne sses, and major coarse-grained sediment input. During the active stage , the coeval basin-fill sequence displays progressive angular unconfor mities, gravitational deposits and subtle changes in thickness with th e sediments unconformably overlying most of the earlier-formed faults. Finally, during the passive stage, the sediments synchronous with dia pir formation include abundant components from the extruding rocks, an d show gentler changes in thicknesses, a progressive decrease in the i nput of coarse sediments, and the deposition of mudstones and/or lacus trine carbonates that clearly extend onto the faulted basin margins.