Geologica Acta, Vol.6, Nº 1, March 2008, 19-42 DOI: 10.1344/105.000000239 Available online at www.geologica-acta.com Structural geology of the Fuegian Andes and Magallanes fold-and-thrust belt – Tierra del Fuego Island 1 2 3 M. MENICHETTI E. LODOLO and A. TASSONE 1 Istituto di Scienze della Terra, Università di Urbino Campus Científico Universitario, 61029 Urbino, Italy. E-mail:
[email protected] 2 Istituto Nazionale di Oceanografia e di Geofisica Sperimentale 34010 Sgonico,Trieste, Italy. E-mail:
[email protected] 3 CONICET- INGEODAV, Dept. de Geología, FCEyN, Universidad de Buenos Aires, Argentina Ciudad Universitaria, 1428 Buenos Aires, Argentina.E-mail:
[email protected] ABSTRACT A synthesis of the structural geology of the Tierra del Fuego Island, which integrates a new data set derived from field surveys and literature data of the last few years, is here presented. The main geological features of the region developed during the Mesozoic-Cenozoic Andean orogenic cycle that started in the Middle to Late Jurassic with a back-arc extension, crustal stretching and widespread volcanism, related to the break-up of Gondwanaland. An extensional fault system deriving from the mechanical and thermal subsidence led the evolution of the Rocas Verdes marginal basin, which hosts the upper Jurassic volcanoclastic rocks, the lower Cretaceous turbiditic sequences and few isolated elongated ophiolitic complexes. From the Late Cretaceous onward, the orogenic cycle of the Fuegian Andes continued with the shortening and inversion of the back-arc margin through horizontal con- traction and crustal thickening. The uplift of the Cordillera, the emplacement of plutonic rocks, and the intraconti- nental polyphase deformation resulted from thick-skinned tectonics.