GRAVITY MODELS OF THE ALPINE STRUCTURE IN THE SPANISH CENTRAL SYSTEM (ZONE NE)

The studied region is located in central Spain, between the Tajo and D uero basins, in the NE area of the Spanish central system. The aim of this paper is to describe the regional Alpine structures and to model them by means of a gravity survey. This region has a basement (Hercyni an metasediments, gneisses and granites) and a cover comprising Jurass ic, Cretaceous and Tertiary sediments. The structure is determined by conjugate wrench faults (N010-degrees-E sinistral and N140E dextral) a nd ENE-WSW north and south vergent thrusts. This structure has been de veloped, during the main compressive Alpine deformation phase (Middle to Upper Miocene); in this phase, the maximum shortening direction is NW-SE. Some structures are Hercynian basement reactivated faults. From a Bouguer anomalies map, the upper crust has been modelled in 2 1/2 D along several cross sections. Gravity models agree with high angle re verse faults affecting both the Mesozoic-Cenozoic cover and the Hercyn ian basement. Then, the thrust tectonics affect both cover and basemen t, without a decollement between them.