Late Holocene marine palynological evidence for short-term cold climatic conditions in the Cormoranes Archipelago, Beagle Channel, southern Tierra del Fuego, Argentina

BORROMEI A.M.; CANDEL, M.S.; MARTINEZ M.A.; QUATTROCCHIO M.; RABASSA J.

Bahía Blanca

Simposio; XIII Simposio Argentino de Paleobotánica y Palinología; 2006

Universidad Nacional del Sur

A fossil marine sequence from Río Ovando (54º 51’ S, 68º 35’ W), Archipiélago Cormoranes, Beagle Channel, has been studied for palynological and marine mollusks content in order to reconstruct paleoenvironmental conditions during the Middle-Late Holocene. The dinoflagellate cyst assemblages from Río Ovando sequence reflect fjord (estuarine) environments close to terrestrial ice field, affected by glacier meltwater discharge, and characterized by short-term oscillations of sea-surface water parameters. At the base of the section, about ca. 4160 14C yr B.P. (4736 cal yr B.P.) (Palynological Subzone RO-2c), is characterized by a high species dinocyst and mollusk diversity followed by a subzone (Palynological Subzone RO-2b) characterized by the presence of Echinidinium-Islandinium complex and monospecific Mytilus mollusk assemblage. This subzone register an inverse correlation between Nothofagus dombeyi type and Echinidinium-Islandinium complex concentration values during ca. 4160 14C yr B.P. (4736 cal yr B.P.) - 4064 14C yr B.P. (4540 cal yr B.P.), suggesting a variable climatic condition, probably related to Neoglacial episodes occurred in the southern Patagonia Andes during this interval. The pollen assemblages led to direct correlations with the onshore palynostratigraphy from southern of Tierra del Fuego. The high percentages of Nothofagus dombeyi type recorded throughout most of the profile strongly suggest the presence of a closed forest, confirming the existence of a variable, cool and wet climate for the Archipiélago Cormoranes area during the Middle-Late Holocene.