Neotectonics in the foothills of the southernmost central

ANDRÉS FOLGUERA, VÍCTOR A. RAMOS, REGINALD HERMANNS, JOSE NARANJO

TECTONICS

AMER GEOPHYSICAL UNION

Año: 2004 vol. 23 p. 1 - 23

0278-7407

The Antinir-Copahue fault zone (ACFZ) is the eastern orogenic front of the Andes between 38 and 37S. It is formed by an east vergent fan of high-angle dextral transpressive and transtensive faults, which invert a Paleogene intra-arc rift system in an out of sequence order with respect to the Cretaceous to Miocene fold and thrust belt. 3.1–1.7 Ma volcanic rocks are folded and fractured through this belt, and recent indicators of fault activity in unconsolidated deposits suggest an ongoing deformation. In spite of the absence of substantial shallow seismicity associated with the orogenic front, neotectonic studies show the existence of active faults in the present mountain front. The low shallow seismicity could be linked to the high volumes of retroarc derivedvolcanic rocks erupted through this faultsystem during Pliocene and Quaternary times. This thermally weakened basement accommodates the strain of the Antin˜ir-Copahue fault zone, absorbing the present convergence between the South America and Nazca plates dextral transpressive and transtensive faults, which invert a Paleogene intra-arc rift system in an out of sequence order with respect to the Cretaceous to Miocene fold and thrust belt. 3.1–1.7 Ma volcanic rocks are folded and fractured through this belt, and recent indicators of fault activity in unconsolidated deposits suggest an ongoing deformation.