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.; MARTÍNEZ, M.A.; QUATTROCCHIO, M.E.; RABASSA, J.

BAHÍA BLANCA

Simposio; 13º Simposio Argentino de Paleobotánica y Palinología; 2006

DEPARTAMENTO de GEOLOGÍA - UNIVERSIDAD NACIONAL del SUR

A fossil marine sequence from Río Ovando (54º 51’ S, 68º 35’ W), Cormoranes Archipelago, Beagle Channel, has been mainly studied for dinoflagellate cysts in order to reconstruct paleoenvironmental conditions during the late Holocene. The dinoflagellate cyst assemblage from Río Ovando sequence reflects fjord (estuarine) environments close to terrestrial ice-field affected by glacier meltwater discharge. The variability in dinoflagellate cyst assemblages could reflect short-term oscillations of sea-surface temperature and seasonal extent of sea-ice cover. The cold climatic conditions prior ca. 4100 14C yr B.P. (Palynological Subzones RO-2c and RO-2a) are interrupted by a coldest period (Palynological Subzone RO-2b). The suggested cooling, characterized by the increasement of “Islandinium-type cyst” and significant decrease in the Nothofagus dombeyi type concentration values (Palynological Subzone RO-2b) after ca. 4100 14C yr B.P., may correlate with Neoglacial episodes occurred in the southern Patagonia Andes Range. The pollen and spore assemblages led to direct correlations with the onshore palynostratigraphy. 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 Cormoranes Archipelago area during the late Holocene. A fossil marine sequence from Río Ovando (54º 51’ S, 68º 35’ W), Cormoranes Archipelago, Beagle Channel, has been mainly studied for dinoflagellate cysts in order to reconstruct paleoenvironmental conditions during the late Holocene. The dinoflagellate cyst assemblage from Río Ovando sequence reflects fjord (estuarine) environments close to terrestrial ice-field affected by glacier meltwater discharge. The variability in dinoflagellate cyst assemblages could reflect short-term oscillations of sea-surface temperature and seasonal extent of sea-ice cover. The cold climatic conditions prior ca. 4100 14C yr B.P. (Palynological Subzones RO-2c and RO-2a) are interrupted by a coldest period (Palynological Subzone RO-2b). The suggested cooling, characterized by the increasement of “Islandinium-type cyst” and significant decrease in the Nothofagus dombeyi type concentration values (Palynological Subzone RO-2b) after ca. 4100 14C yr B.P., may correlate with Neoglacial episodes occurred in the southern Patagonia Andes Range. The pollen and spore assemblages led to direct correlations with the onshore palynostratigraphy. 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 Cormoranes Archipelago area during the late Holocene. A fossil marine sequence from Río Ovando (54º 51’ S, 68º 35’ W), Cormoranes Archipelago, Beagle Channel, has been mainly studied for dinoflagellate cysts in order to reconstruct paleoenvironmental conditions during the late Holocene. The dinoflagellate cyst assemblage from Río Ovando sequence reflects fjord (estuarine) environments close to terrestrial ice-field affected by glacier meltwater discharge. The variability in dinoflagellate cyst assemblages could reflect short-term oscillations of sea-surface temperature and seasonal extent of sea-ice cover. The cold climatic conditions prior ca. 4100 14C yr B.P. (Palynological Subzones RO-2c and RO-2a) are interrupted by a coldest period (Palynological Subzone RO-2b). The suggested cooling, characterized by the increasement of “Islandinium-type cyst” and significant decrease in the Nothofagus dombeyi type concentration values (Palynological Subzone RO-2b) after ca. 4100 14C yr B.P., may correlate with Neoglacial episodes occurred in the southern Patagonia Andes Range. The pollen and spore assemblages led to direct correlations with the onshore palynostratigraphy. 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 Cormoranes Archipelago area during the late Holocene. A fossil marine sequence from Río Ovando (54º 51’ S, 68º 35’ W), Cormoranes Archipelago, Beagle Channel, has been mainly studied for dinoflagellate cysts in order to reconstruct paleoenvironmental conditions during the late Holocene. The dinoflagellate cyst assemblage from Río Ovando sequence reflects fjord (estuarine) environments close to terrestrial ice-field affected by glacier meltwater discharge. The variability in dinoflagellate cyst assemblages could reflect short-term oscillations of sea-surface temperature and seasonal extent of sea-ice cover. The cold climatic conditions prior ca. 4100 14C yr B.P. (Palynological Subzones RO-2c and RO-2a) are interrupted by a coldest period (Palynological Subzone RO-2b). The suggested cooling, characterized by the increasement of “Islandinium-type cyst” and significant decrease in the Nothofagus dombeyi type concentration values (Palynological Subzone RO-2b) after ca. 4100 14C yr B.P., may correlate with Neoglacial episodes occurred in the southern Patagonia Andes Range. The pollen and spore assemblages led to direct correlations with the onshore palynostratigraphy. 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 Cormoranes Archipelago area during the late Holocene. LATE HOLOCENE MARINE PALYNOLOGICAL EVIDENCE FOR SHORT-TERM COLD CLIMATIC CONDITIONS IN THE CORMORANES ARCHIPELAGO, BEAGLE CHANNEL, SOUTHERN TIERRA DEL FUEGO, ARGENTINA A. M. Borromei1, M. S. Candel1, M. Martinez1, M. Quattrocchio1 and J. Rabassa2 1CONICET - Departamento de Geología, Universidad Nacional del Sur, San Juan 670, B8000ICN   Bahía Blanca, Argentina. E-mail: borromei@criba.edu.ar 2Laboratorio de Geología del Cuaternario, CADIC-CONICET, CC 92, 9410 Ushuaia, Tierra del  Fuego, Argentina A fossil marine sequence from Río Ovando (54º 51’ S, 68º 35’ W), Cormoranes Archipelago, Beagle Channel, has been mainly studied for dinoflagellate cysts in order to reconstruct paleoenvironmental conditions during the late Holocene. The dinoflagellate cyst assemblage from Río Ovando sequence reflects fjord (estuarine) environments close to terrestrial ice-field affected by glacier meltwater discharge. The variability in dinoflagellate cyst assemblages could reflect short-term oscillations of sea-surface temperature and seasonal extent of sea-ice cover. The cold climatic conditions prior ca. 4100 14C yr B.P. (Palynological Subzones RO-2c and RO-2a) are interrupted by a coldest period (Palynological Subzone RO-2b). The suggested cooling, characterized by the increasement of “Islandinium-type cyst” and significant decrease in the Nothofagus dombeyi type concentration values (Palynological Subzone RO-2b) after ca. 4100 14C yr B.P., may correlate with Neoglacial episodes occurred in the southern Patagonia Andes Range. The pollen and spore assemblages led to direct correlations with the onshore palynostratigraphy. 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 Cormoranes Archipelago area during the late Holocene.