FAULT NETWORK IN RIO COLCA VALLEY BE TWEEN MACA AND PINCHOLLO, CENTRAL ANDES, SOUTHERN PERU

The network of faults and joints within the Mesozoic, Miocene and PleistoceneHolocene formations was studied in the Rio Colca valley, in the PincholloLariMaca area (Central Andes, southern Peru). A complex, multi-phase development of these structures was revealed. The results show that the structural framework of the Rio Colca valley consists of WNWESE and NESW faults, and a few WE faults. The strike of the most common fault sets is approximately parallel (longitudinal) or perpendicular (transverse) to the WE oriented strike of stratification surfaces in the Mesozoic sedimentary series and the WE fold macro-structures, developed in these strata. Diagonal faults and joints are less common, although at some localities they are numerous. The recurrence of major fault systems throughout the Mesozoic and Miocene series and the PleistoceneHolocene (mainly colluvial) deposits is proof of recent, tectonic activity in the study area. The recent faulting has led to the development of a system of distinct, primary fault scarps, tectonic grabens and horsts, as well as open fissures, which are well marked in the surface morphology, and in many cases have not yet been eroded.