Abstract
The Salar de Atacama basin of northern Chile preserves stratigraphic evidence for the evolution of the Andean cycle. It has evolved from a non-arc-related rift, through back-arc and inter-arc stages, to a Neogene fore-arc basin. Accumulation of the sedimentary succession was mainly due to extensional faulting. Important but short-duration contractional episodes do link to known fast-order plate-margin changes, but their stratigraphic effect appears to be restricted to uplift/erosion rather than creation of significant flexural subsidence.
The Salar de Atacama basin originated as part of a regional rift system during Permian time and contains 2 km of Permo-Triassic continental detritus and volcanic rocks. The area remained above depositional base level throughout Late Triassic to Late Cretaceous time. Syn-rift continental red beds were deposited to a thickness of at least 2 km on a parallel rift segment in the Domeyko area to the west. Continued Triassic-Jurassic extension in the Domeyko basin resulted in a classic continental to marine transition, with deposition of a 2 km+ Jurassic mixed carbonate/clastic sequence.
In latest Cretaceous-Eocene time, the Salar basin was an arc-related basin and accommo-dated some 4 km+ of continental detritus (Purilactis Group) due to back-arc extension, sediment being derived from the Domeyko Cordillera and arc rocks to the west. Late Eocene right-lateral strike-slip faulting and associated restraining bend uplift were driven by a high rate of oblique convergence between the Farallon and South American plates. This deformation complicated the stratigraphy of the Purilactis Group and inverted the western basin margin, which formed the dominant provenance area for a 2-km-thick Oligocene continental basin-fill component (Paciencia Group).The Oligocene basin was an extensional to trans-tensional basin.
The Miocene-Holocene Salar basin is a continental fore-arc basin. This latest segment of the basin fill comprises pyroclastic and continental sedimentary rocks thrust over Quaternary gravels in many places. The Cordillera de la Sal is an intrabasinal uplift, initiated as a thin-skinned contractional feature. Thus, the superposed basin-fill components represent responses to distinctly different geodynamic settings.
