Development of a continental forearc: A Cenozoic example from the Central Andes, northern Chile

In order to understand the response of a continental forearc to changes in subduction-zone geodynamics, we constructed a high-resolution chronostratig raphic cross section across the Central Andean forearc of northern Chile (2 1 degrees-24 degrees S), The tectono-stratigraphic development of the forea rc differs from established models. No relationship was found between chang es in rate of relative plate convergence and amount and style of deformatio n. Forearc response to continual compression since the Oligocene has been u plift and segmentation into discrete tectonostratigraphic zones. From west to east, these zones are the extensional Coastal Cordillera, the extensiona l and/or transtensional Central depression, and the transpressional and/or compressional Precordillera-Preandean depression. Each area has recorded al most continuous sedimentation from Oligocene (?Eocene) time to the present day, Accommodation space has been generated by basin-margin uplift rather t han active subsidence, We propose a model in which uplift of the leading ed ge of the South American plate is driven by subcrustal accretion of materia l removed at the trench by subduction erosion. Uplift and subduction erosio n result in the trenchward gravitational collapse of the plate edge. The te ctono-stratigraphic complexity exhibited within the Central Andean forearc is likely to be representative of Cordilleran-type margins and would be dif ficult to recognize in an ancient continental forearc.