PERCHED DUNES IN THE FUEGIAN STEPPE, SOUTHERN ARGENTINA

ANDREA CORONATO; MÓNICA SALEMME; JIMENA ORÍA; FLORENCIA MARI

Earth System Sciences (Editorial Springer), Advances in Geomorphology 2

Springer-Nature

Año: 2020; p. 58 - 91

The description of the genesis and the geomorphological characteristics of three perched dunes, named as O´Connor, Amalia and Arturo is presented herein. They are located in the periphery of the shallow lakes of such name, which have a semi-perennial nature in the Fuegian steppe (lat. 53° S). These landforms are characterized according to their location, orientation and quantity, as well by color, thickness and textural composition of the eolian origin units and the units with soil development. These units, considered as paleosoils, are indicators of stable environments that would have diminished the eolian accumulation which is responsible for the formation of eolian units of variable thickness. A chronological sequence, based upon radiocarbon dating on organic matter belonging to each one of the units transformed into soils, fits quite well with already published absolute dates and it allows the interpretation of the evolution of these dunes formed since the Late Glacial to the Late Holocene. An eolian accumulation rate for the Amalia and Arturo dunes is suggested, based upon the thicknesses of each unit and the obtained radiocarbon dates. The tephras contained in the Amalia and Arturo dunes are described and compared with the Middle Holocene eruption of Mt. Burney (Chile). The characteristics of archeological record and its state of conservation are analyzed, whether they are lithic materials or bone remains. The chronology obtained for the paleosoil sequence with is discussed in relation to paleoenvironmental events. These events are determined on the base of certain proxies, both in the studied soils as in lacustrine cores obtained in shallow lakes from the surroundings. The development of some of the paleosoils is in contrast with certain regional examples that appear in the literature. From the archeological point of view, the development of dune geomorphological processes such as auto-erosion or ?cannibalism? and re-deposition exposed the possible existence of taphonomic traps and palimpsests; these are generally visible in surface contexts, which are interpreted as archeological reservoirs. In this kind of sites, the resolution is low and usually, the degree of mixture could be high.