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Paleoenvironmental reconstruction by pollen analysis from loess sequences of the southeast of Buenos Aires (Argentina)

1993; Elsevier BV; Volume: 17; Linguagem: Inglês

10.1016/1040-6182(93)90076-r

1873-4553

Marta M. Paez, Aldo R. Prieto,

Lichen and fungal ecology

A model of the dynamics of pollen dispersion and deposition in relation to loess deposition is proposed. It is based on pollen analysis of three discontinuous loess sequences of Late Pleistocene-Holocene age, that are located at the archaeological locality of Cerro La China, Buenos Aires Province, Argentina (37° 57′ S.; 58° 37′ W.). Deposition and accumulation of loess and pollen were interpreted in terms of their provenance and transport using the Tauber (1967) and Pye (1987) models for pollen and dust dispersal, respectively. Three pollen zones can be distinguished based on changes in pollen assemblages. The final Late Pleistocene-Early Holocene interval is represented by pollen zone 3. Loess deposits have been accumulated in an environment with a locally high effective moisture. Loess deposition would have occurred synsedimentarily with extra-regional, local and regional pollen taxa. The relationship between pollen dispersal and possible extra-regional pollen sources indicate predominantly W.-SW winds. This zone is truncated by an erosive episode, hence, the successional process of the community could not be reconstructed for the Early Holocene. The Middle Holocene is represented by pollen zone 4. Deposition of loess began in an environment with predominantly herbaceous communities. Pollen concentration increases towards the top of the zone and may represent a buried soil; this would imply a change towards more stable and humid conditions than those at the beginning of the deposition. Extra-regional pollen concentration suggests a comparatively high local and regional pollen productivity rather than a change in wind direction. A slight erosive episode constitutes the upper boundary of zone 4 and is related to new drier conditions. Zone 5 occurs during historical times and is represented by graminous steppe communities and over-representation of local taxa.