Tectosedimentary evolution of the Payogastilla Group and and its relationto Cenozoic volcanic arc, in the Calchaquí, Tonco and Amblayo valleys, Salta province, Argentina

Acta geológica lilloana 26 (1): 2014

Abstract

The stratigraphic and sedimentological characteristics of Payogastilla Group depositsare very important to study tecto-sedimentary evolution of the Andean foreland basin in north-western Argentina. The lower stratigraphic boundary of Payogastilla Group with the LumbreraFormation (Santa Barbara Subgroup, Salta Group) deposits is a paraconformity. The upperstratigraphic boundary, the Colorados Formations is a paraconformity and a unconformity, thesubsidence of the basin was uniform and the duration of the initial deposit was about ~35 to21 Ma. During the middle to upper Miocene, represented by Angastaco Formation deposits,with a thickness of 4550 m (in Calchaquí river) and 1500 m (in Tonco) it took place a major tectonic influence, which delimited the basin depocenter in Angastaco basin. This event start-ed in Tonco valley (>13.7 Ma) and later continued in Calchaquí valley (~13 Ma). Also in the~13 Ma it have developed two orographic barriers (Los Colorados and León Muerto ranges),in the eastern, that during the Late Miocene (10-5 Ma) would have been reactivated to animportant orographic chains form. During the Pliocene the tectonic uplifts would have reacti-vated, being registered as alluvial fans with a strong provenance from the east. Levels tuffdeposits intercalated in Angastaco and Palo Pintado formations, show a clear signature of thearc indicating their origin of the arc active to those times with features that indicate a crustalcomponent in their magmas participant. While pyroclastic levels intercalated in San FelipeFormation, with higher peraluminous character and lower Na20 K20 content regarding, whichlie in the area of the type S granites, giving different cortical components idea