|
Circum-Pacific and Caribbean Orogens |
Department of Geology and Mineralogy, University of Adelaide, South Australia 5001
The Andean orogen varies considerably along its length. Between the Galapagos and Chile Rises, from approximately 0° to 46° S., the orogen is flanked by the Peru-Chile submarine trench to the west and by the Gondwana Shield with its platform cover to the east. A major change in trend occurs at about 18° S. and the orogen is widest in the region of this inflexion. The segment studied, which is notable for its largely non-marine and highly volcanic character, lies immediately south of the inflexion. Continuity of the eastern zones in the segment with more southerly parts of the orogen is interrupted by the Pampean Ranges which project into the belt from the south-east (Fig. 1).
Segment: the segment described here lies between 20° and 25° S. and is 600 km long measured parallel to the strike. For the main Mesozoic geosyncline of the Western Andes, the segment is extended to 29° S. (i.e. a total length of 1000 km) for some data.
Zones: six zones are distinguished. From west to east they are—1. The Coast Range, composed of eugeosynclinal Jurassic rocks, deformed and intruded at the end of the Jurassic and block-uplifted in Tertiary times. 2. The Longitudinal Valley zone, comprising miogeosynclinal Jurassic and Cretaceous, deformed and intruded in U. Cretaceous times. 3. The Central Andes (Puna zone), a platform in the Mesozoic, with continental U. Cretaceous-Tertiary basins, Tertiary deformation and major later Tertiary volcanism. 4. The Pampean Ranges of Argentina, a block-faulted zone with significant Devonian deformation. 5.
...
This 250-word extract was created in the absence of an abstract.
