A STRUCTURAL OUTLINE OF THE SERRA DE TRAMUNTANA OF MALLORCA (BALEARIC ISLANDS)

The structural and stratigraphic aspects of the Balearic Islands are described by outlining the geology of the Serra de Tramuntana. This range is part of the southeastern margin of the Valencia trough and has the typical features of thrust tectonic areas. A stratigraphic column, a structural map and three cross-sections show the main features of this range. Thrusts dip to the southeast and are arranged in an imbricate system with a transport direction to the NW. The thrusts recorded involve Upper Paleozoic to Middle Miocene rocks. Imbricates-bearing thin slices and duplexes developed where thin sequences with pronounced competency contrasts exist. Folds are also present: they usually trend NE-SW, except in local areas where they are interpreted as being associated with oblique ramps. Fold axes plunge sub-horizontally and folds face the northwest. Thrust displacements of up to 10 km are deduced from the existence of klippes and windows, and shortening of around 50% is deduced from a comparison of deformed and restored cross-sections. The onset of the main contractional event is pre-Miocene (probably Late Oligocene) in age, but major thrust emplacement occurred during the Middle Miocene. The widespread occurrence of compression structures in the Balearic Islands developed from late Oligocene to Middle Miocene put strong constraints on the models explaining the origin of both the Valencia trough and the Algerian basin. The first must be considered, at least in part, as the Balearic foreland basin and the second could be superimposed on the internal zone of the western Mediterranean orogenic belt.