Uso del espacio de cazadores recolectores y paleoambiente Holoceno en el Valle del Río Cisnes de Aisén, Chile

This paper presents results on archaeological research conducted at the Cisnes river basin (~44° S), valley which passes through several environments in western Patagonia, from the westernmost limits of the steppe to the Pacific channels. These are assessed in light of a palaeoenvironmental reconstruction spanning from the Late Pleistocene to the Holocene. Results allow interpreting different ways for approaching the environment; these are exposed both spatially and chronologically. Cultural units defined occupied the space discontinuously and ranking it differentially attending to environmental variability. We correlate our data with available archaeological information for Aisén and adjacent areas. Additionally, we discuss cultural continuity and eventual interaction of steppe hunter-gatherers with peoples from the western archipelagic area

Oldest record of the scale-leaved clade of Podocarpaceae, early Paleocene of Patagonia, Argentina

A new podocarpaceous conifer is described from the early Danian Salamanca Formation (southern Chubut, Patagonia, Argentina) based on compressions of leafy branches with cuticular remains. Kirketapel salamanquensis gen. et sp. nov. has amphistomatic, scale-like leaves with marginal frills distinguishable at the apex; stomata oriented randomly in relation to the major axis of the leaf with four to five subsidiary cells and extremely reduced Florin rings; and irregularly shaped epidermal cells. We compare K. salamanquensis with extant and extinct members of the imbricate-leaved podocarps, among which it closely resembles Florin’s Dacrydium group C genera (i.e., Lagarostrobos, Manoao, Lepidothamnus and Halocarpus). Among these genera, only Lepidothamnus has a living representative in South America, the Chilean L. fonkii, whose leaf macro- and micromorphological characters are described in detail for comparison. Overall, the Patagonian fossil species is most similar to the extant and extinct members of Lagarostrobos in its cuticular micromorphology; however, macromorphological characters, such as the leaf size, apex curvature and mode of flattening, clearly differentiate it from all four genera of Dacrydium group C. We include Kirketapel salamanquensis in a combined molecular and morphological phylogenetic analysis conducted under the maximum parsimony criterion. The new, early Paleocene fossil taxon is confidently recovered as part of the scale-leaved clade as defined herein, which also includes Halocarpus, Phyllocladus, Lepidothamnus, Parasitaxus, Lagarostrobos and Manoao, and it constitutes the oldest record known for the group by at least 17 million years as well as its first fossil occurrence outside Australasia, establishing a widespread Gondwanan history. Furthermore, based on its oldest locality of occurrence, K. salamanquensis shows that the divergence of the total group of the scale-leaved podocarps occurred by at least 65 million years ago, adding to the growing systematic knowledge of earliest Cenozoic macrofloras in the Southern Hemisphere.Fil: Andruchow Colombo, Ana. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Museo Paleontológico Egidio Feruglio; ArgentinaFil: Escapa, Ignacio Hernán. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Museo Paleontológico Egidio Feruglio; ArgentinaFil: Carpenter, Raymond J.. University of Tasmania; AustraliaFil: Hill, Robert S.. University of Adelaide; AustraliaFil: Iglesias, Ari. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; ArgentinaFil: Abarzua, Ana M.. Universidad Austral de Chile; ChileFil: Wilf, Peter. State University of Pennsylvania; Estados Unido

Regional vegetation and climate changes during the last 13 kyr from a marine pollen record in Seno Reloncaví, southern Chile

International audienceA marine pollen record from Seno Reloncaví (southern Chile, 41°S) illustrates temperate rainforest changes during the last 13 cal kyr BP. Our study shows the end of the last Termination at ~ 11.5-12 cal kyr BP coincident with the expansion of Weinmannia, illustrating disturbance and warming conditions, at the expense of cold-resistant conifers (Fitzroya-Pilgerodendron and Podocarpus). Warming conditions are strengthened at 10.7 cal kyr BP by the increase of heliophytic taxa (Eucryphia-Caldcluvia) characteristic of the Valdivian rainforest. These heliophytic taxa reach their maximum expansion between 9.6 and 7.4 cal kyr BP and point to warm and dry conditions during the Holocene Climatic Optimum. After 7.4 cal kyr BP, vegetation changes indicate variable climate conditions superimposed on a cooling trend associated with an increase in precipitation after ~ 6-5 cal kyr BP, shown by the expansion of the cold-resistant conifers. During the late Holocene, after 2.8 cal kyr BP, the continuous expansion of cold-resistant conifers marks an increase of cool and wet conditions. The comparison between marine and terrestrial pollen records highlights the similar trends and timing of vegetation changes that allows to complete the regional pattern of vegetation changes around Seno Reloncaví. In comparison with the terrestrial pollen records, this marine pollen record provides a more regional signal of vegetation/climate changes and clearly demonstrates the sensitivity of marine pollen records to past vegetation and climate change

Postglacial vegetation, fire and climate dynamics at Central Chilean Patagonia (Lake Shaman, 44ºS)

A 19 cal ka BP pollen and charcoal record from Lake Shaman (44°S; 71°W, Chile) was analyzed to establish vegetation, fire and climate dynamics of the forest-steppe ecotone in Central Chilean Patagonia. Lake Shaman record indicates that the upper Río Cisnes valley was free of ice at around 19 cal ka BP. From this date and until 14.8 cal ka BP, a grass steppe with high proportions of shrubs associated to colder and drier conditions than present developed in this area. A continuous increase of Nothofagus accompanied by a decline in the steppe shrubs and sudden dominance of paludal over aquatic plants from 11 cal ka BP was associated to effective moisture increase but still under modern values. The replacement of the cold-dry grass-shrub steppe by a similar-than-present forest-steppe ecotone suggests an increase in temperature indicating the onset of the Holocene. At the same time, moderate fire activity suggested by the charcoal record could be related to major fuel availability as consequence of Nothofagus forest expansion. Between 8 and 3 cal ka BP, the record indicates the easternmost position of the forest-steppe ecotone suggesting the highest effective moisture with the establishment of seasonality between 5 and 3 cal ka BP. From 3 cal ka BP, the record indicates a retraction of the forest-steppe ecotone accompanied by a high pollen record variability and an increased fire activity. These late changes suggest decreased effective moisture associated with a high climatic variability. At regional and extra-regional scale, climatic changes at Lake Shaman's record are mostly associated to changes (latitudinal shifts and/or strengthening/weakening) of past Southern Westerlies that were previously recorded along Patagonia from the Lateglacial to the mid-Holocene. During the Late Holocene, a regional pattern characterized by high record variability emerges throughout Central Chilean Patagonia. This variability would be related to (1) low magnitude Southern Westerlies changes probably associated to ENSO and/or SAM or (2) the complex relationships between vegetation, fire and human occupations during the last 3 cal ka

Sedimentary record from Patagonia, southern Chile supports cosmic-impact triggering of biomass burning, climate change, and megafaunal extinctions at 12.8 ka

The Younger Dryas (YD) impact hypothesis posits that fragments of a large, disintegrating asteroid/ comet struck North America, South America, Europe, and western Asia -12,800 years ago. Multiple airbursts/impacts produced theYD boundary layer (YDB), depositing peak concentrations of platinum, high-temperature spherules, meltglass, and nanodiamonds, forming an isochronous datum at >50 sites across similar to 50 million km(2)of Earth's surface. This proposed event triggered extensive biomass burning, brief impact winter, YD climate change, and contributed to extinctions of late Pleistocene megafauna. In the most extensive investigation south of the equator, we report on a similar to 12,800-year-old sequence at Pilauco, Chile (similar to 40 degrees S), that exhibits peak YD boundary concentrations of platinum, gold, high-temperature iron- and chromium-rich spherules, and native iron particles rarely found in nature. A major peak in charcoal abundance marks an intense biomass-burning episode, synchronous with dramatic changes in vegetation, including a high-disturbance regime, seasonality in precipitation, and warmer conditions. This is anti-phased with northern-hemispheric cooling at the YD onset, whose rapidity suggests atmospheric linkage. The sudden disappearance of megafaunal remains and dung fungi in the YDB layer at Pilauco correlates with megafaunal extinctions across the Americas. The Pilauco record appears consistent with YDB impact evidence found at sites on four continents