NORTHERN CHILE SUBDUCTION PLATE-BOUNDARY AND QUATERNARY UPLIFT

At subduction plate boundaries, it is commonly expected that relatively strong vertical motions occur. The coast of northern Chile, like that of southern Peru (Goy et al., 1992; MacharC & Ortlieb, 1992; Ortlieb et al, 1995a; 1996) did register such positive vertical deformation that is linked to the subduction of the Nazca plate below the South-American plate (Barazangi and Isacks, 1976). Emerged marine terraces are preserved along long stretches of the northern Chile coast (Radtke, 1989). Recent studies focused on the idenufication, age determination and morphostratigraphy of the remnants of Pleistocene shorelines, to decipher the neotectonic behaviour of the 1000 km-long coastal segment located south of the Peruvian border. The methodology points to a quantification of the vertical deformation, at a 10'y scale, and to the detection of variations in locdregional uplift rates during the late and middle Quaternary. The study also deals with the determination of differential vertical movements between structural blocks, and the obtention of a chronostratigraphical framework for the reconstitution of Quaternary faulting activity in the coastal area.. At the present stage of the co-operative project, we completed a general reconnaissance of the Quaternary marine terraces in the whole study area, and realised detailed studies in the sector between Antofagasta and Hornitos (Ortlieb et al., 1995b 1997). Geological, paleontological an