An early-middle Holocene section in Bahia Lapataia (54 degrees 50'S, 68 degrees 34' W), Beagle Channel, Tierra del Fuego, Argentina has been examined taking into account its sporomorphs and organic-walled microplankton. The palynological assemblage suggests nearshore environments. Two relatively higher sea levels were identified by the increased abundance of organic-walled dinoflagellate cysts (Brigantedinium spp., Selenopemphix sp., Operculodinium centrocarpum sensu Wall and Dale, Spiniferites spp.), the acritarch Halodinium sp. and zoomorph remains (test linings of foraminifera and copepod egg-envelopes). The littoral vegetation at the time of the marine incursion was mainly arboreal, as can be seen in the pollen records by significant increase in Nothofagus dombeyi type frequencies, while a forest-steppe vegetational pattern developed regionally. After comparison with another nearby fossil marine terrace, the palynological analysis has demonstrated that these terraces represent the same transgressive-regressive event. The relative altitudinal differences between these terraces in the area may be the result of seismotectonic activity during the Holocene.
