Subantarctic macrotidal flats, cheniers and beaches in San Sebastian Bay, Tierra Del Fuego, Argentina

Abstract

San Sebastian Bay is a large, semicircular coastal embayment situated on the Atlantic coast of Tierra del Fuego,
Argentina. It is a high-energy, subantarctic environment with a tidal range of 10.4 m, influenced by large waves of Atlantic
and local origin and swept by constant, strong westerly winds. A 17 km long gravel spit protects the Northern part of the
Bay giving rise to a gradient in sedimentary processes. From south to north, are seven distinct sedimentary environments.
Coastal sedimentation started at least 5200 years before present BP. and a rapid progradation related to a relative sea-level
drop has infilled about 6 kilometres of the Bay with a sedimentary sequence 10–11 m thick. 14-C dating of unabraded shells
in the Chenier ridges of the relict part of the complex allows for a precise reconstruction of the stages of the progradation,
that has slowed from 2.35 mryear at 5000 years BP to 0.6 mryear at present. The possible causes of the sea-level drop are
discussed.