Geology and Geochronology of Cabo Blanco, Santa Cruz

Abstract

Cabo Blanco is located on the Atlantic coast, at the southern end of Golfo San Jorge (47°12' LS). The cape exposes rocks that were first identified by Darwin as quartzites comparable to those currently included in the Bahía Fox Formation of the Malvinas Islands. This correlation was followed by several authors who worked in the area up to the present. However, other authors interpreted these rocks as volcanic and included them within the Jurassic volcanism of extra-Andean Patagonia. In order to confirm the age of the possible Paleozoic quartzitic rocks, a field reconnaissance and a geochronological study were carried out. The zircons analyzed by U-Pb from two samples showed an age of 182.47 ± 2.01 Ma and 174.60 ± 2.46 Ma. According to the geological and geochronological study carried out, the occurrence of Paleozoic metamorphic and/or sedimentary rocks at Cabo Blanco as mentioned by different authors since the 19th century are discarded. The interpretations that the outcropping rocks at Cabo Blanco are of volcanic and sedimentary origin and of Jurassic age included within the Chon Aike magmatic province are confirmed.