PALEOZOIC TERRANES OF SALAR DE NAVIDAD, A NTOFAGASTA REGION, CHILE

The Paleozoic rocks which crop out at Salar de Navidad, previously kno wn as 'Estratos del Salar de Navidad' were studied. Two formations can be distinguished: Formacion Sierra del Tigre and Formacion Cerros de Cuevitas. They differ in lithology, age, depositional environment and tectonic setting. A strong angular unconformity is observed between bo th formations. Formacion Sierra del Tigre is composed by a turbiditic sequence with 1,500 to 2,000 m thickness. A Devonian age is based on t he presence of Mucrospirifer. Flute casts suggest southern-southeast s ense of detrital supplies. Provenance of continental block and recycle d orogen is inferred from the composition of sandstones, although some volcanic influence is suggested. Diabasic sills and dikes of tholeiit ic affinity intrude the sequence. These sandstones are more feldspathi c, and different from coeval deposits of the High Cordillera of Antofa gasta. Structural characteristics are that of a broken formation, whos e structures evolved during a deformational event, contemporaneously o r prior to diagenesis. Abundant cracks were produced during the deform ation an subsequently filled with quartz, which is the proof that a hi gh fluid pressure dominated deformation. This formation is affected by a weak metamorphism characterized by the following mineral associatio n: white mica, chlorite, quartz and albite. Deposition, deformation an d metamorphism took place during the 'Toco Orogenesis'. Formacion Cerr os de Cuevitas is a 461 m thick sequence composed by quartzitic sandst ones, shales and conglomerates with interbedded coquinaceous limestone s and some tuffs. An Early Permian age is well documented for this for mation, that is inferred from the following fossil forms: Kochiproduct us peruvianus, Euconospira arizaroensis and Myalina. Stratigraphical a nd sedimentological characteristics suggest a stable platformal deposi tion environment.