Field trip guide; Neogene evolution of the central Andean Puna Plateau and southern Central Volcanic Zone
Field trip guide; Neogene evolution of the central Andean Puna Plateau and southern Central Volcanic Zone (in Field trip guides to the backbone of the Americas in the Southern and Central Andes; ridge collision, shallow subduction, and plateau uplift, Suzanne Mahlburg Kay (editor) and Victor A. Ramos (editor))
Field Guide (Geological Society of America) (2008) 13: 117-181
This seven-day field trip is designed to examine the distinctive magmatic, structural, and sedimentological features of the late Oligocene to Recent evolution of the southern part of the high central Andean Puna plateau and the southern Central Volcanic Zone magmatic are. The stops for Days 1-5 between 23 degrees and 27 degrees S latitude in Argentina emphasize the distinctive magmatic and structural features of the Puna region, which comprises the southern half of the central Andean Puna-Altiplano plateau. Differences between the northern and southern Puna are highlighted. Among the features to be observed are (1) giant Miocene ignimbrites of the northern Puna, (2) distinctive normal and strike-slip faults and associated shoshonitic lavas of the central Puna, (3) the intraplate and calc-alkaline lavas of the southern Puna, (4) the silicic calderas of the southern Puna, and (5) internally drained salar basins. The stops for Days 6 and 7 between 26.5 degrees and 27.5 degrees S latitude in Chile present a view of the Miocene to Recent frontal arc region on the western side of the plateau. The stops particularly highlight the late Miocene to Pliocene displacement of the magmatic arc front from the Maricunga Belt on the western edge of the plateau to its present position in the Central Volcanic Zone. Evidence for the timing of plateau uplift, changes in the angle of the underlying subduction zone, delamination of the underlying continental crust and mantle lithosphere, and forearc subduction erosion are examined throughout the course of the trip. DISCLAIMER: This is not a geologic field guide to be used in the traditional sense of a detailed road log, but rather a survey of the southern Puna region that can be done with the use of Google Earth. Latitude and longitude coordinates are given for all stops in WGS84 (world geodetic system) coordinates that can be used with Google Earth (downloadable from the Web) or any other georeferenced imagery. Driving instructions are given where access is possible by paved or high-quality unpaved roads that are present on road maps that are generally available in the region. Due to the lack of information on available road maps, changing driving conditions, and the need for caution in accessing the sites, precise instructions are not given for others. A significant number of these stops are on primitive, unmaintained roads or tracks that require a serious four-wheel drive vehicle, an experienced off-road driver, and supporting equipment (winch, spare tires, jack, etc.) to navigate safely. Many of the stops are in the Atacama Desert, where there is almost no water. The majority of the stops are at high elevations-most are between 3500 and 4500 m (-11,500-14,750 ft); all are over 2000 m (6500 ft). Attention needs to be paid to the potential for altitude sickness (called the Puna in Argentina). There are no cell phone towers, no service stations, or towing facilities in most of the region to bail you out! The availability of fuel can be questionable at times. Contact a knowledgeable guide to the region before attempting to use this field guide in the more isolated parts of the area.