An Alpine-style Ordovician collision complex in the Sierra de Pie de palo, Argentina: Record of A-subudction beneath the Famatina arc.

VAN STAAL, C.R.; VUJOVICH, G.I.; CURRIE, K.L.; NAIPAUER, M.

JOURNAL OF STRUCTURAL GEOLOGY

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2011 vol. 33 p. 343 - 361

0191-8141

The Caucete Group and structurally overlying Pie de Palo Complex in western Argentina are characterisedby two generations of west-verging folds and thrust-related shear zones, which formed underamphibolite facies conditions. The Caucete Group is separated from the Pie de Palo Complex by thePirquitas thrust. These structures are interpreted to have formed as a result of a progressive deformation,generated during Middle Ordovician, underthrusting of the Laurentian-derived Cuyania microcontinentbeneath the active Famatina margin. Geometrical relationships are most simply explained if the Pie dePalo Complex was basement to the Caucete Group prior to Ordovician orogenesis. We propose that thisbasement-cover relationship was established during Cambrian rifting of the Cuyania microcontinentfrom Laurentia. The Pirquitas fault may have been initiated during this extension prior to its long-livedremobilization as a thrust. We cannot rule out the possibility that the Pie de Palo Complex was exoticwith respect to the Caucete Group, but for this to be possible we have to introduce an extra generation ofstructures, for which no evidence is preserved.The deformation was characterised by early strain localization followed by a more homogeneouslydistributed non-coaxial flow during F2. Thermal softening probably dominated over fabric softeningduring this stage.