THE PALAEOENVIRONMENT OF BYERS PENINSULA, SOUTH SHETLAND ISLANDS, ANTARCTICA

PARICA, C.; REMESAL, M. B.; SALANI, F. M.

Otro; 22th Latinoamerican Colloquium; 2011

Byers Peninsula exposes marine outcrops of Jurassic times with deep marine deposits (Anchorage Formation). After a transitional period, a non marine regime took place in cretaceous times, established near 130 Ma and dated on volcanic rocks emplaced in a continental environment (Parica et al., 2007). The outcrops of several basaltic and basandesitic lava flows with columnar junction are representative of water presence. Former papers from other authors considered these structures as subvolcanic bodies (Cerro Negro, Clark Nunatak and others). This non marine basin is ferns rich and a strong volcanism marked the features since the Cretaceous to Tertiary. Based on the study of sedimentary rocks and their structures a seasonal regime, with rainfalls, and high energy environment could be defined, inferred. Sedimentary rocks and their structures are typical of a seasonal regime, with rainfalls, and high energy environment The carbonate deposits in lagoons were the tool to apply stable isotopes studies (δ18O for palaeotemperatures, and δ13C for environment). Anyway, some peperitic breccias in the Ratón Hill suggest the simultaneity in shorts distances of sea water and fresh water in the non marine environment. Data from the analyzed samples have values for δ13C since -10.6 to -15.9‰ and δ18O de 0.5 a -2.8‰. These sensitive data confirm the non marine regime for the deposited carbonates,and the equilibrium rank of temperatures was established in between 15 to 20°C. The upper Mesozoic and Tertiary environmental setting is determined by the palaeoflora, sedimentary features and the stable isotopes analytical data (Parica, 2008). Some of the family ferns determined still continue alive in the Patagonian Andean forests (Cesari et al., 1998).