Palynofacial analysis in alkaline soils and palaeoenvironmental implications: the Paso Otero 5 archaeological site (Necochea District, Buenos Aires Province, Argentina). In Press.

GRILL S.; BORROMEI A.; MARTINEZ G.; GUTIERREZ M.; CORNOU M.; OLIVERA D.

JOURNAL OF SOUTH AMERICAN EARTH SCIENCES

Elsevier Science Ltd.

Lugar: USA; Año: 2007 p. 34 - 47

0895-9811

The combination of the palynofacial and sedimentological analyses constitutes a valuable method for paleoenvironmental and paleoclimatic reconstructions, specially when fossil pollen information is scarce or absent. This methodology is used to study a late Pleistocene/Holocene sequence at Paso Otero 5 archaeological site, middle basin of the Quequén Grande river, Necochea district, Buenos Aires province, Argentina. Although the main factor responsible for the destruction of pollen grains is pH, the biochemical and chemical oxidation, and mechanical damage contribute to the deterioration of the material as well. The site sequence indicates that extremely arid climatic conditions without vegetation cover prevailed during the late Pleistocene. After this period the climate changed to semiarid conditions associated with disturbed environment due to strong eolian activity (Palynofacies 1 and 2; pre-10,400 RCYBP). During the Pleistocene/Holocene transition (Palynofacies 3 and 4; ca. 10,400-9400 RCYBP), loamy facies, associated with paleosoils, reflect stable conditions and temporary ponds (spring deposits). Similar conditions are registered towards the end of early Holocene (Palynofacies 5,6,7,8 and 9, ca. 6600 RCYBP). From middle to early late Holocene (Palynofacies 10, 11, 12, 13 and 14, ca. 6600-4200 RCYBP) sandy and silty facies are associated with flood margin of streams or rivers. The top of the sequence  (Palynofacies 15 and 16), represent alluvium sediments, and reflect locally humid conditions and modern vegetation with anthropic influence.