Late Glacial pioneer vegetation and paleoenvironments in the Beagle Channel, Tierra del Fuego, southernmost Argentina: preliminary results.

SAVORETI A.; CANDEL, M.S.; FERNANDEZ, M.; SUÁREZ, G.L.; IGLESIAS, A.; PONCE, F.

San Salvador de Bahía

Congreso; International Organization of Paleobotany Conference; 2016

We interpret Late Glacial vegetational communities andpaleoenvironments from a peat bog located in the north coast of the BeagleChannel, southernmost South America, based on plant macrofossils, palynologyand diatoms. The Harberton peat bog is located 700 m north of the BeagleChannel coast, in an inter-drumlin area into a drumlin field formed during theLate Pleistocene glaciation (Last Glacial Maximum, 24.000 yr BP) when the frontof the Beagle glacier reached Punta Moat, about 60 km east of the study area.Laminated silty-clay deposits were identified in the base of the peat core(between 10.37 and 9.94 m).We analyzed this basal portion of the core with the aim to identify the pioneerspecies that colonize the first deglaciated land, before the development ofextensive peat bogs in the area. The base of the silty-clay sequence has been radiocarbondated as 16,152 yr BP and the top as 13,298 yr BP. First results show thepresence of two main groups of plant macrofossils: angiosperms and Bryophyta s.s.The angiosperms include 3 families [Poaceae, Cyperaceae and Ericaceae] and thebryophytes include 9 families with 10 taxa [Amblystegiaceae (Limprichtia), Bryaceae (Bryumpseudotrichetrum), Dicranaceae, Dicranellaceae (Dicranella), Ditrichaceae (Distichium capillaceum), Hypnaceae (Isopterygiopsis.), Meesiaceae (Meesiauliginosa), Plagiotheciaceae (Plagiothecium),and Sphagnaceae]. Samples were analyzed each 5cm, to study the palynomorphs anddiatoms content. The palynomorphs identified in the studied section arerepresented by Nothofagus dombeyitype, Poaceae, Gunnera, Empetrum rubrum, Cyperaceae, Myriophyllum andSordaria-type fungi spores. The aquatic palynomorphs are represented by microfossiltype 181 (van Geel). The diatom analysis showed the presence of fragilarioidsin all basal sequence. In summary, the pioneer vegetation development in thisrecently deglaciated land mainly that included herbs (Poaceae and Cyperaceae), heath(Empetrum rubrum) and wet and rocky mosses(Isopterygiopsis, Plagiothecium). The low frequency andconcentration values of Nothofagus pollenimply sources from distant forest. These preliminary data show the presence ofa shallow lagoon environment close to recently deglaciated land, affected by local glacier meltwater discharge.