Ordovician back arc foreland and Ocloyic thrust belt development on the western Gondwana margin as a response to Precordillera terrane accretion -: art. no. TC4008

The Famatina belt, southern central Andes, records a circa 470 m.y. shortening episode (Ocloyic orogeny) affecting the peri-Gondwanan back arc basin in response to the accretion of the Precordillera terrane. Collision created distinct features across and along the margin, some of which persisted into the present Andean structure. From east to west, the Ocloyic deformation is recorded across the telescoped region of Famatina, represented by ( 1) an east vergent fold-thrust belt (EVFTB) involving a major angular unconformity between Early and Middle Ordovician rocks, ( 2) a highly deformed volcano-sedimentary belt, and ( 3) an east vergent ductile shear zone affecting Famatinian granites. Axis attitudes of Ordovician refolded anticlines in the EVFTB show west-east tectonic transport, in agreement with kinematics of Ocloyic high-strain belts, indicating shortening orthogonal to the present Pacific margin. Eastward displacement of the Ordovician volcanic arc at similar to27degreesS latitude together with a documented sinistral slip zone across the proto-Andean margin suggests tectonic indentation.