Initial Late Holocene Vegetal Communities Inferred from Archaeological Sites in Northeastern Patagonia (Argentina): Anthrachological Evidence from the Site Zoko Andi 1

JO SÁNCHEZ; M BREA ; AF ZUCOL; G MARTÍNEZ ; GA MARTÍNEZ

Mendoza

Congreso; 4th Southern Deserts Conference; 2014

Universidad Nacional de Cuyo

The principal aim of this work is to present a preliminary floristic characterization of the environmental conditions which would have prevailed during the Initial Late Holocene in the lower basin of the Colorado River by applying anthracological information. This area is located in a semi-arid ecotonal landscape, crossed by an allochthonous river which flows into the Atlantic Ocean. Archaeological sites usually present scarce and very fragmentary anthrachological records although Zoko Andi 1 site has preserved an important amount of archaeological charcoals. This site presents two archaeological components related to distinct temporal periods from the Late Holocene. Charcoal assemblages were obtained from the lower component dated at ca. 1500?1300 years BP, which corresponds to the Initial Late Holocene. Radiocarbon data were obtained from both charcoal and bones. All charcoal fragments recorded are dispersed in stratigraphic position associated to cultural materials in a defined sector of the stratigraphy: units 5 and 6 (sensu Martínez et al., in press). The dispersed charcoals were employed to identify trees and/or shrubs found in the area around hunter-gatherers? settlements. Charcoals are usually a sign of human selection and use of forest resources. The archaeological charcoals were identified by examining freshly fracture surfaces in transversal, radial, and tangential sections using reflected light. They were identified using standard wood key, wood atlases and descriptions by diverse authors and InsideWood Database (http://insidewood.lib.ncsu.edu/). The terminology for the wood features follows the IAWA Lists of Features Suitable for Harwood Identification. Charcoal remains were compared to extant species, particularly present-day taxa from south-central Argentina. The analysis of 94 samples of archaeological charcoal enabled the following species to be identified: Prosopis caldenia (36%), Prosopis flexuosa (2%), Senna aphylla (21%), Jodina rhombifolia (8%), Condalia microphyllia (20%) and Larrea divaricata (13%) related to Leguminoseae-Mimosoideae, Leguminoseae-Caesalpinioideae, Santalaceae, Rhamnaceae and Zygophyllaceae, respectively. On the one hand, Prosopis and Condalia (58%) are hardwoods and therefore have high caloric values and long combustible duration. They are an excellent source of heat and were probably used for heating, cooking and lighting. On the other hand, Senna, Jodina and Larrea could have been used for fire starting. Anthracological analyses of the charcoal assemblages recorded in Zoko Andi 1 demonstrated that during the Initial Late Holocene the woody vegetation of this region corresponded to a xerophytic open environment composed by xeric trees and shrubs where trees and thick thorn scrub were interrupted by herbaceous gaps. This vegetation developed under an arid to semi-arid climate.