INVESTIGADORES
ISLA Federico Ignacio
artículos
Título:
Paleoenvironmental reconstruction of Holocene coastal deposits...
Autor/es:
ESPINOSA, M; DE FRANCESCO, C; ISLA F
Revista:
Journal of Paleolimnology
Editorial:
Kluwer Acad Publisher
Referencias:
Año: 2003 vol. 29 p. 49 - 60
ISSN:
0921-2728
Resumen:
An estuarine sequence outcropping at La Ballenera Creek (Buenos Aires Province), dated between 6,800 and
14 4,100 C years BP, was investigated for diatoms and molluscs. The sea level history along the Buenos Aires
coastline has been reconstructed from discrete beach ridge sequences along low-lying plains. The La Ballenera
profile is located on a cliff coast where a sequence recorded environmental changes. Fifty-eight diatom species
were grouped based on their salinity and life form characteristics. Cluster analysis allowed the division of the
sequence into three diatom zones. Mollusc tolerances were also used to discern the environmental changes induced
by sea-level fluctuations. The base of the sequence recorded the initiation of the marine influence about
6,790?6,200 years ago. Diatom assemblages consist of brackish-freshwater tychoplankton accompanied by
brackish benthic diatoms. Among the molluscs, the freshwater-brackish species Heleobia parchappii dominates.
14 Between 6,200 and ca. 4,800 C years BP, an estuarine lagoon environment is indicated by benthic and epiphytic
14 marine-brackish diatoms, as well as by the estuarine snail Heleobia australis. After 4,800 C years BP, the diatom
assemblages and the relative abundance of freshwater molluscs indicate a marshy environment with lower salinity
content. The La Ballenera records the salinity changes that affect an estuary that infilled during the 2,700 years
after the maximum sea level reached in mid-latitudes of South America.