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

摘要

San Sebastian Bay is a large, semicircular coastalembayment situated on the Atlantic coast of Tierra del Fuego,Argentina. It is a high-energy, subantarctic environment with atidal range of 10.4m, influenced by large waves of Atlantic andlocal origin and swept by constant, strong westerly winds. A 17kmlong gravel spit protects the Northern part of the Bay giving rise toa gradient in sedimentary processes. From south to north, are sevendistinct sedimentary environments, Coastal sedimentation startedat least 5200 years before present (BP) and a rapid progradationrelated to a relative sea-level drop has infilled about 6 kilometresof the Bay with a sedimentary sequence 10-11m thick. 14-C datingof unabraded shells in the Chenier ridges of the relict part of thecomplex allows for a precise reconstruction of the stages of theprogradation, that has slowed from 2.35m/year at 5000 years BPto 0.6m/year at present. The possible causes of the sea-level dropare discussed.