THE PALAEOENVIRONMENT OF BYERS PENINSULA, SOUTH SHETLAND ISLANDS, ANTARCTICA.

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

Heidelberg

Otro; 22nd International Collquium on Latein Amerikan Earth Sciences; 2011

Ruprecht-Karls-Universität Heidelberg

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, stablished near 130 Ma and dated on volcanic rocks emplaced in a non marine environment (Parica et al., 2007). The outcrops of several basaltic and basandesitic lava flows with columnar disjunction 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. Sedimentary rocks and their structures let to understand 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 environmental frame for the upper Mesozoic and Tertiary is sustained 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). According paleomagnetic reconstructions the location of the area for those times was close to the actual one, 62° South Latitude.