Tectonic Setting of the Magallanes Basin, Chile

Abstract

Abstract The Magallanes Basin is a retroarc foreland basin (Suarez and Pettigrew, 1976; Dalziel, 1981; Wilson, 1991: Fildani and Hessler, 2005) and the sedimentary sequence preserved in the Andean fold-thrust belt reflects the early extensional phase of basin evolution and the subsequent contractile phase with eventual uplift associated with Andean orogenesis (Figs. i.1 and i.2). In the latest Jurassic, extension associated with the initial breakup of southern Gondwana (Bruhn, et al., 1978; Gust, et al., 1985; Pankurst, et al., 2000; Calderón et al., 2007) culminated in the development of an oceanic backarc basin referred to as the Rocas Verdes Basin (Katz, 1963). Ophiolitic rocks exposed in the Cordillera Sarmiento, south and west of Parque Nacional Torres del Paine, represent the obducted remains of the floor of this backarc basin (Wilson, 1991; Fildani and Hessler, 2005; Calderón et al., 2007). Compression associated with the onset of the Andean orogeny resulted in rapid uplift along the western basin margin and concurrent foreland subsidence. A deep-water depositional phase, caused by flexural loading of obducted ophiolitic blocks over the attenuated crust, is marked by the turbidites of the Punta Barrosa Formation (Fig. i.1). The overlying shale-rich Upper Cretaceous Cerro Toro Formation represents the climax of deep-water sedimentation. Conglomerate-filled channel systems (channel belt up to 8 km wide) within the Cerro Toro Formation developed along much