El Holoceno Medio en valles fluviales del sudeste pampeano: ¿Escasez de sitios o de unidades portadoras? Una perspectiva geoarqueológica

In this paper, the study of the stratigraphy and chronology of seven archaeological sites located in the streams Cortaderas, Cristiano Muerto and Tapalqu e (province of Buenos Aires, Argentina) is presented. The aim of this study is to evaluate if the absence and/or low representation of the geological deposits corresponding to the Middle Holocene in these low-order streams is conditioning the archaeological signal in the southeastern pampas.  Our results show that deposits corresponding to this time period are scarce and that erosional uncorformities between Late Holocene and Late Pleistocene or Early Holocene units are common. Besides, this situation is observed in sites located in other low-order streams in the southeastern pampas. Thus, the low archaeological signal for the Middle Holocene in many fluvial valleys could be the result, at least in part, of this stratigraphic bias. Furthermore, the soils/paleosoils developed in the fluvial sequences have condensed the cultural evidence. This generates an image of periods of more intense human occupation and archaeological hiatus that could be the result of the fluvial dynamics. This stratigraphic scenario in low-order streams is valid not only for the studied area but also has implications for the chronology and preservation of archaeological sites in fluvial sequences in many valleys in Argentina.