Introduction to the Cerro Toro Formation in the Silla Syncline

Abstract Outcrop accessibility: easy Outcrop Coordinates: 51.1199°S, 72.9701°W Refer to outcrops 4 and 5 on location map The Silla Syncline is located within the Torres del Paine National Park east of Lago Pehoe and south of Lago Nordenskjöld. The Cerro Toro Formation in the area comprises more than 1100 m of deep-water strata within which Crane (2004) recognized and mapped three major coarse-grained channel complexes. These correspond to the informally named Pehoe, Paine and Nordenskjöld members, from oldest to youngest (Figs. iii.1, iii.2). The Pehoe channel complex, consists of two conglomerate units, Pehoe A and B, separated by a 100-m-thick sequence of thick-bedded sandstones and thin interbedded mudstone units (see outcrop #4). The Paine member is subdivided into the Paine A, Paine B, Laguna Negra debris flow deposit, and the Paine C (see outcrop #5). Paine C is the largest channel in the section with a width of 2.5 to 3 km and a minimum thickness of 200 m (Figs. iii.1, iii.3 and iii.4). The Nordenskjöld member is exposed as a near continuous, roughly circular outcrop in the axis of the syncline north of the park highway (Fig. iii.3). This member is divided into two major subdivisions, Nordenskjöld A and Nordenskjöld B, separated by a thick debris flow deposit (Figs. iii.1 and iii.4). The various channel complexes throughout the Silla Syncline section shifted locations as they were emplaced. The