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GUBBELS, T. L., and B. L. ISACKS, Cornell University, Department of Geological Sciences, Ithaca, NY, and J. M. ELLIS, Chevron Overseas Petroleum Inc., San Ramon, CA

ABSTRACT: Applications of Satellite Imagery and Digital Topography to the Construction of a Crustal-Scale Transect Across the Central Andes at 20 degrees S Latitude

The central Andean plateau is one of the Earth's most remote and poorly mapped regions. The plateau has an average elevation of 3.7 km, and extends from central Peru to at least 30 degrees S latitude. The plateau and flanking Subandean foldthrust belt (FTB) reach their greatest width near 20 degrees S, and at this latitude both the FTB and the basin within the plateau (Altiplano basin) are areas of active hydrocarbon exploration. We have used Landsat TM imagery, stereoscopic SPOT imagery, and digital topography to construct a crustal-scale transect across the central Andes in order to better understand Andean tectonics at this latitude.

Beginning at the Peru-Chile trench and continuing to the east, the transect crosses the Coastal Cordillera, Longitudinal Valley, Active Magmatic Arc, Altiplano basin, Eastern Cordillera, Subandean fold-thrust belt, and Subandean foreland basin. A digital elevation model across the entire region illustrates that the magmatic arc, Altiplano basin, and Eastern Cordillera all lie within the plateau region. Satellite imagery across the transect illustrates the characteristic geology, structure, and geomorphology of each of the major morphotectonic regions, as well as the nature of their boundaries.

The transect has led us to a number of new insights on Andean tectonics at this latitude. Most importantly, it supports a two-stage model of Andean Cenozoic growth in which a widespread Oligocene to mid-Miocene compressional deformation in the Altiplano and Eastern Cordillera is followed in the late Miocene and Pliocene by thrusting localized east of the Eastern Cordillera, forming the Subandean fold-thrust belt.

AAPG Search and Discovery Article #90988©1993 AAPG/SVG International Congress and Exhibition, Caracas, Venezuela, March 14-17, 1993.