Evolution of the Early Paleozoic mélange at the eastern margin of the Argentine Precordillera

At the eastern margin of the Argentine Precordillera, Early Paleozoic clastic sediments occur which are interpreted to represent sedimentary mélange deposits of (? Ordovician-) Silurian age. Their olistolith content as well as different pebble types from conglomerate olistoliths provide information about the sedimentary history and the source areas of clastic input during preSilurian times. Gravitational sliding of the olistoliths into an eastern basin was followed by a compressional event during Late Devonian to pre-Upper Carboniferous times. The latter is interpreted to be the result of a ± W-E crustal shortening between the Eastern Precordillera and a basement complex to the east. Late Tertiary compression affected the already steeply inclined and deformed deposits. There was no evidence found to postulate large-scale strike-slip faulting between the Eastern Precordillera and the Sierras Pampeanas Basement Complex during Paleozoic and/or Tertiary times. The formation of both the eastern clastic deposits of the Precordillera and the western slope of the Cambro-Ordovician carbonate platform is interpreted to be the result of large-scale crustal extension with block rotations during Middle to Late Ordovician times.