The Miocene Torres del Paine Granite is a sill-like subhorizontal laccolithic body. It is elliptical in plan view and its major axis extends for more than 12 km. In profile the section is strongly asymmetric, with a maximum thickness decreasing from 2.5 km in the west towards zero in the east. The laccolith is emplaced along a shallow to subhorizontal thrust fault (the Rio Nutrias Fault), that is associated with internal folding and faulting developed during an early, pre-intrusion, thin-skinned tectonic phase that affected the Cerro Toro Formation. Where the intrusive shows its thicker section it connects downwards with a feeder dyke that dips more than 70 degrees west. This feeder dyke is emplaced along and reutilizes an old high-angle reverse fault (probably an inherited normal fault) that juxtaposes the Cerro Toro (to the east) and the Punta Barrosa (to the west) formations. This fault, thought to be related with a period of thick skinned tectonic shortening, causes a several kilometer uplift of the western block and consequent erosion of the stratigraphic cover. The compressional reactivation of faults at an angle equal to or greater than the mechanical frictional lock-up angle (approximately 60 degrees) requires, at least locally, the development of prefailure supralithostatic fluid pressures (lambda greater than or equal to 1 or P-m greater than or equal to S-v = S-3) The principal stress orientation during high-angle reverse fault reactivation implies the synchronous generation of dilation-extension structures. In this case, these would have been lenticular and horizontal, giving rise to several lenses that were connected with and filled by magma along the fault. In the case of Torres del Paine, faulting and syntectonic intrusion were possible only in those faults that were large enough to connect themselves with a reservoir or magma chamber that provided the required fluid or lubricant to enable displacement. The formation of the laccolith corresponds to the contemporaneous dilation of the extensional structure associated with the reverse faulting, developed at a depth of about 5 km below the paleosurface, an amount that is is significantly larger than the undeformed stratigraphic thickness of the overlying rocks. From these calculations, and from the geological evidence, it is concluded that the overburden consisted of preintrusion structural repetitions of the stratigraphy.