Taphonomic studies of surface lithic scatters from the coastal area of San Matias Gulf, Rio Negro Province, Argentina

EUGENIA CARRANZA; MARCELO CARDILLO; JIMENA ALBERTI; CRISTIAN FAVIER DUBOIS

Tunuyán

Congreso; 4th Southern Deserts Conference; 2014

Laboratorio de Paleo-Ecologia humana, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Cuyo

TAPHONOMIC STUDIES OF SURFACE LITHIC SCATTERS FROM THECOASTAL AREA OF SAN MATÍAS GULF, RÍO NEGRO PROVINCE, ARGENTINAThe research area             The coast of San Matías Gulf ?RíoNegro province, Argentina- runs along 380 linear km and can be divided into twosectors, North and West, each with different geological and geomorphologicalcharacteristics, resulting in a differential space use by hunter-gathererspopulations who occupied the area during the Middle and Late Holocene (ca. 6000-450 years BP). The temperatesemi-arid climate predominates in the area with rainfall varying between 100and 350 mm per year. The aeolian processes are the main materialstransportation, erosion and redepositional agents and are a very importantforce of sorting and alteration of the archaeological record. Thesearchaeological materials are located mainly in surface deposits being found intwo different landforms with differential dynamic process -dunes and terraces-. Objectives and methodology            The main goal of this paper is topresent the methodology we used for analyzing the formational history of lithicscatters affected by surface erosion processes in our study area. Through theapplication of actualistic analysis and the statistical modeling wecharacterize lithic assemblages from different contexts of the northern coastof the Gulf. Taking into account the differences in resolution and integrity ofthe archaeological record, we explore patterns of differential exposition andpreservation among the studied loci.              To recover the artifacts we employed a distributionalmethodology in which the sample units were 2 m2 grids, where werecovered 958 artifacts. The sampling was done carrying out a taphonomiccontrol, which involved marking the exposed face of each artifact in order toreconstruct the original position of each piece. To fulfill this objective weconsigned:- face of recovery of each artifact (side A or B), - the abrasion stage of each face (W), - position change and relative stability - volume of each artifact. Also, we collected an assemblage redeposited by wind action. In order tocompare different levels of weathering frequency we used a Chi2test. Changes in position and relative stability were registered as dichotomicvariables and were used in regression models along with the volume of eachartifact. In all cases the level of significance was 0.05. Analysis and results            The comparison of weathering levels by area indicatessignificant differences among them, with certain loci with higher and lower frequency of different weatheringlevels. A significant correlation among volume and position change, and volumeof the redeposited assemblages and volume of the archaeological ones wasobserved. Discussion            The results suggest that thepost-depositional history is different among the different loci. Some of them suggest a relatively recent exposure, as thereis a predominance of the early stages of weathering on both sides. On the contrary,other assemblages show the predominance of higher weathering stages, which isconsistent with the longer exposure of these materials on highly deflatedterraces, forming pavements. The volume distribution of the lithic materialsand of the redeposited assemblage together shows that both groups havedifferent distribution. This along with what was observed in the redepositedscatters can be experimentally contrasted, generating certain criteria toevaluate position changes/burial and the differential removal of artifacts inrelation to its volume. Allthis would indicate different levels of exposure and preservation according to artifactsdepositional contexts. Therefore, the study of the consequences of theseprocesses on the conformation of surface archaeological sites provides clues tointerpret the redundancy in the space use over time.