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

SAVORETTI, A.; CANDEL, M.S.; FERNÁNDEZ, M.; SUARÉZ, G.; IGLESIAS, A.; PONCE, J.F.

Salvador, Bahía

Congreso; XIV International Palynological Congress and X International Organisation of Palaeobotany Conference; 2016

Asociación Latinoamericana de Paleobotánica y Palinologia; Universitate

We interpret Late Glacial vegetational communities and paleoenvironments from a peat bog located in the north coast of the Beagle Channel, southernmost South America, based on plant macrofossils, palynology and diatoms. The Harberton peat bog is located 700 m north of the Beagle Channel coast, in an inter-drumlinarea into a drumlin field formed during the Late Pleistocene glaciation (Last Glacial Maximum, 24.000 yr BP) when the front of 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 pioneer species that colonize the first deglaciated land, before the development of extensive peat bogs in the area. The base of the silty-clay sequence hasbeen radiocarbon dated as 16,152 yr BP and the top as 13,298 yr BP. First results show the presence of two main groups of plant macrofossils: angiosperms and Bryophyta s.s. The angiosperms include 3 families [Poaceae, Cyperaceae and Ericaceae] and the bryophytes include 9 families with 10 taxa [Amblystegiaceae (Limprichtia), Bryaceae (Bryum pseudotrichetrum), Dicranaceae, Dicranellaceae (Dicranella), Ditrichaceae (Distichium capillaceum), Hypnaceae (Isopterygiopsis.), Meesiaceae (Meesia uliginosa), Plagiotheciaceae (Plagiothecium) and Sphagnaceae]. Samples were analyzed each 5cm, to study the palynomorphs and diatoms content. The palynomorphs identified in the studied section are represented by Nothofagus dombeyitype, Poaceae, Gunnera, Empetrum rubrum, Cyperaceae, Myriophyllum and Sordaria-type fungi spores. The aquatic palynomorphs are represented by microfossil type 181 (van Geel). The diatom analysis showed the presence of fragilarioids in 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 and concentration values of Nothofagus pollen imply sources from distant forest. These preliminary data show the presence of a shallow lagoon environment close to recently deglaciated land, affected by local glacier meltwater discharge.