The central and eastern parts of the Sierra de Pie de Palo (Western Sierras Pampeanas, Argentina) are formed by a Mesoproterozoic basement and a Neoproterozoic sedimentary cover. Both were involved in an accretionary orogeny (penetrative deformation and metamorphism) along the southwestern margin of Gondwana in the Ordovician (i.e., Famatinian Orogeny). New U–Pb SHRIMP detrital zircon ages from the Neoproterozoic Difunta Correa Metasedimentary Sequence (DCMS), record the characteristics of this region at the time of sedimentation. Detrital zircon ages range from Neoarchean to Neoproterozoic, with main peaks at ca. 1.0–1.3 Ga and ca. 1.35–1.5 Ga. Geological and geochronological evidences from the DCMS suggest that the sediments were derived from both, the Grenville province and the Granite-Rhyolite province in the southeastern side of present Laurentia, and from the nearby Grenville-age basement of Western Sierras Pampeanas. This latter basement has been interpreted as the result of the accretion and reworking of the South American Paleoproterozoic MARA craton to southeastern Laurentia during the Grenvillian Orogeny, which remained juxtaposed throughout the Neoproterozoic. The detrital zircon patterns of the DCMS support the hypothesis that this sequence was deposited in the Puncoviscana/Clymene Ocean during the Ediacaran at the southeastern passive margin of MARA. This craton eventually broke away from Laurentia in the late Neoproterozoic-early Paleozoic, which led to the opening of the Iapetus Ocean. MARA drifted along the Proto-Pacific Ocean, and finally collided against the southwest Gondwana margin during the Cambrian (i.e., Pampean Orogeny).

MINECO/CGL2009-07984

Peer reviewed