PALYNOLOGY AND MARINE MOLLUSKS ASSEMBLAGES FROM BAHÍA LAPATAIA, BEAGLE CHANNEL, TIERRA DEL FUEGO, ARGENTINA. FIRTS EVIDENCES FROM HOLOCENE MARINE TRANSGRESSION

CANDEL, M.S.; MARTÍNEZ, M.A.; GORDILLO, S.; CORONATO, A.; RABASSA, J.

University of Victoria, Canada

Workshop; International Workshop on Pacific Dinoflagellate Cysts; 2009

School of Earth and Ocean Sciences, University of Victoria, Canada.

Palynological and marine mollusk analyses from Aserradero Lapataia 1, 2 and Arroyo Baliza sites, Tierra del Fuego, were performed in order to investigate the distribution and paleoenvironmental conditions of dinoflagellate cyst and molluscan assemblages in high latitudes of the Southern Hemisphere. The dinocyst assemblages of Aserradero Lapataia 1 and 2 are dominated by Peridiniales and are mostly composed by Brigantedinium cariacoense, B. simplex, B. spp., Echinidinium granulatum, E. spp., Selenopemphix quanta, accompanied by Lejeunecysta sp., and other indeterminate round brown cysts. Also, acritarchs, covers of benthonic foraminifers and copepod eggs are dominant. The mollusk associations are characterized by Mulinia edulis, Mytilus chilensis, Aulacomya atra and Yoldia sp. The radiocarbon dates on Mulinia edulis shells gave ages of 8094 +/-43 and 8167 +/-43 14C yr B.P. for Aserradero Lapataia 1 and 2, respectively. At Arroyo Baliza, dinoflagellate cysts assemblage includes Brigantedinium spp., Echinidinium granulatum, E. spp., Selenopemphix quanta, cf. S. quanta, Votadinium calvum, Quinquecuspis concreta and other round brown dinocysts, accompanied by acritarchs and copepod remains. Marine mollusk association is composed by Venus antiqua, Aulacomya atra and Mytilus chilensis, among others. The radiocarbon dating on Venus antiqua shells yielded 2844 +/- 34 14C yr B.P. The present dinocyst assemblages reflect fjord (estuarine) environments close to terrestrial ice field affected by glacier meltwater discharge with variable salinities in all localities. The presence of Zygnemataceae and Botryococcus in association with Prasinophyceae (Tasmanites sp.) confirms a marginal marine environment influenced by fluvial discharge. The palynofacies analysis shows a dominance of translucent phytoclasts accompanied by amorphous organic matter in subordinate proportions, suggesting short distances and/or a short period of transport from the terrestrial source area. The marine deposits of the Aserradero Lapataia 1 and 2 sites confirm the oldest ages known for the estuaric phase of Holocene transgression in the Beagle Channel. The Arroyo Baliza deposit provides new evidence for the regressive phase during late Holocene.