Tafonomía y tecnología lítica en un ambiente altamente dinámico: El caso de la pinguinera del islote La Pastosa (Pcia. de Río Negro) Patagonia, Argentina [Taphonomy and lithic technology in a highly dynamic environment]

Abstract

Taphonomy and lithic technology in a highly dynamic environment: The case of the penguin colony of La Pastosa Islet (Río Negro Province), Patagonia, Argentina

This paper presents the first results of taphonomic and technological analyses of the lithic assemblage recovered on La Pastosa Islet, on the coast of Río Negro province, Patagonia, Argentina. This archaeological record is particular because it has been under a high formational dynamic and is located in an area recently occupied by a colony of Magellan penguins (Spheniscus magellanicus). Two samplings of lithic material were made, for which technological, metric and taphonomic variables were registered.

La Pastosa is an 8 hectare islet, which is located 768 m. from the continent, and is only attached to it at low tide by a narrow land strip that runs through a marsh. While the absolute age of this island is unknown, we know that from the late Holocene, around 3000 BP, sea level reached current levels (Favier Dubois 2013), and since that time the islet was visited by hunter-gatherers, who buried their dead in the highest part of the island (Favier Dubois et al. 2007, Favier Dubois et al. 2009). Today, this area has a great biodiversity, such as a reproductive colony of sea lions (Otaria flavescens) which has recently formed (Svendsen et al. 2009: 8) as well as a variety of seabirds.

Artifact sampling was focused on the area of greatest density of lithic artifacts, currently close to the center of the islet (Figure 1). The context of recovery of these materials can be divided into three categories: A) common transit areas of penguins that give shape to paths free of vegetation; B) burrow entrances C) marginal spaces that correspond to sectors of debris accumulation (twigs and dry grass, feathers, Penguin carcasses) on the margins of the transit area (Figure 2).

During sampling, the original position of the artifacts, or face of recovery, and context of discovery were recorded. At the lab, general typological (tool, core, or debitage), raw materials, metrics (volume in mm3), and taphonomic variables were registered. The latter in particular were used to characterize and compare both assemblages.

The recording and analysis of artifact modification due to taphonomic processes is a line of research to approach the intensity of the physical transformations in the archaeological context, and to indicate their degree of integrity (Schiffer 1983; Burroni et al. 2002). The variables recorded were as follows, the level of weathering in each tool face (W: W0, W1, W2, W3); the presence of carbonate concretion; and the integrity of the piece (whole or broken).

The results show that intensive penguin traffic and burrow activity exposed buried materials in certain sectors (Figure 5.1), which are pushed through paths with no vegetation (Figure 5.2) and redeposited in “fall off” areas with little or no circulation (Figure 5.3). These are mostly small patches of vegetation and organic waste, which have high relative stability. For this reason we believe that in these patches, materials are more likely to accumulate and perhaps re-enter into the substrate. Preliminary evidence obtained for this study area suggests that the lithic record is in continuous formation, in this case because of the action of penguins. Since the establishment of this colony is recent, its impact on the archaeological record is significant.