tuffs. To the southeast of Cáchira, Norte de Santander, andesitic porphyry copper deposits in mineralizations of chalcopyrite and bornite occur in the Girón Formation. Stratigraphy and depositional environment The Girón Formation in large areas of its extent overlies the Precambrian Bucaramanga Gneiss, in the northern area the Arboleda Granite, and the Carboniferous to Permian Diamante Formation in the area around Toledo, Norte de Santander. In this part, the formation is overlain by the Río Negro and Tibú-Mercedes Formations. In the central area at the type locality in the Lebrija River valley, the formation unconformably overlies the Bocas Formation and is overlain by the Tambor Formation. On the Mesa de Los Santos and the Bucaramanga Massif, the formation overlies the Jordán Formation with an angular unconformity dipping 10 to 15°. In the central part it is overlain by the Rosablanca Formation. In the southernmost extent of the formation, along the road from Busbanzá to Corrales, the Girón Formation unconformably rests upon the Floresta Formation. The formation forms the economic basement in the Middle Magdalena Valley. The age has been estimated to be Late Jurassic, ranging from Oxfordian to Tithonian, based on ostracods and palynomorphs. Stratigraphically, the formation is time equivalent with the Buena Vista Breccia of the proximal area of the Llanos Basin and the Arcabuco Formation to the west of the Boyacá Fault. The formation was deposited in an alluvial to fluvial or fluvio-lacustrine terrestrial environment, with fast-flowing braided rivers and in certain parts meandering river deposition to a deltaic environment. Towards the top of the stratigraphic unit, the deposition became shallow marine. The overall tectonic regime represented an extensional basin setting. The rifting of the Jurassic and Early Cretaceous, resulting from the break-up of Pangea, caused large variations in thickness of the Girón Formation. Provenance The grains composing the Girón Formation have been analyzed using X-ray diffraction, resulting in quartz as principal component (73 to 97%), and clay minerals belonging to the kaolinite group (2 to 4%) and illite-mica (3-19%). It has been suggested a main component of the provenance for the sediments was the Devonian Floresta Formation. Tectonics The Girón Formation probably deposited as a result of regional uplift of the Santander and Floresta Massifs in the Late Jurassic. The formation is folded in an anticline around the type locality producing the Los Cobardes Anticlinal that extends to Contratación. Transpressive tectonic movements after deposition produced five sets of