Sedimentological, malacological, and pollen analyses from 14C-dated alluvial sections from the Luján River provide a detailed record of environmental changes during the Holocene in the northeastern Pampas of Argentina. From 11,200 to 9000 14C yr B.P., both sedimentary and biological components suggest that the depositional environment was eutrophic, alkaline, and freshwater to brackish shallow water bodies without significant water circulation. During this time, bioclastic sedimentation was dominant and the shallow water bodies reached maximum development as the climate became more humid, suggesting an increase in precipitation. Short-term fluctuations in climate during the last stage of this interval may have been sufficient to initiate changes in the water bodies, as reduction of the volume alternated with periods of flooding. The beginning of the evolution of shallow swamps in the wide floodplain or huge wetlands was contemporaneous with a sea level lower than the present one. From 9000 and 7000 14C yr B.P., mesotrophic, alkaline, brackish, probably anoxic swamps existed. Between 7000 and 3000 14C yr B.P., anoxic calcareous swamps were formed, with subaerial exposure and development of the Puesto Berrondo Soil (3500–2900 14C yr B.P.). A trend to a reduction of water bodies is recorded from 9000 to ca. 3000 14C yr B.P., with a significant reduction after ca. 7000 14C yr B.P. A shift to subhumid–dry climate after 7000 14C yr B.P. appears to be the main cause. During this time, an additional external forcing toward higher groundwater levels was caused by Holocene marine transgression causing changes in the water bodies levels. The climate became drier during the late Holocene (ca. 3000 yr B.P.), when clastic sedimentation increased, under subhumid–dry conditions. Flood events increased in frequency during this time. From ca. A.D. 1790 to present, the pollen record reflects widespread disturbance of the vegetation during the European settlement.

No abstract

No abstract

The aim of the present contribution is to assess whether the abundance of mollusk species in the Southern Pampas (Argentina), an environmentally homogeneous region, reflect the local conditions of water bodies. In order to test this hypothesis, a comprehensive study was conducted in 30 sites regularly distributed across the region. At each site, the abundance of mollusk species was determined, and a series of physico-chemical measurements taken. Principal Component Analysis (PCA) and Cluster Analysis (CA) were used for the ordination of sampling sites based on the measured environmental variables. In addition, Canonical Correspondence Analysis (CCA) was conducted to explore the relationships between environmental variables and mollusk abundances. Mollusk species were represented by the gastropods Biomphalaria peregrina, Chilina parchappii, Heleobia parchappii, Physa acuta, Pomacea canaliculata, Stenophysa marmorata, Uncancylus concentricus and the bivalve Musculium argentinum. Although aquatic vegetation cover, conductivity, and substrate were among the main parameters influencing mollusk distribution, their effect was insufficient to explain the spatial distribution pattern of the species in a regional scale. It is because the Southern Pampas is a very homogeneous area, and the ranges of these environmental conditions are within the range of ecological tolerance of most of the species represented. Yet, some species resulted good indicators of environmental conditions at local (microhabitat) scale, i.e., particular microhabitats that occur in different water bodies as well. In fact, even distributed in many different water bodies along the Southern Pampas C. parchappii is always linked to lotic environments, and U. concentricus is exclusively restricted to hard substrata. On the other hand, H. parchappii is the only species represented in mesohaline waters and P. acuta appeared to be a good indicator of pollution in the area.

The growth of the Ficopomatus enigmaticus reefs was measured throughout a coastal lagoon at di¡erent temporal and spatial scales (over 24 years, annually and monthly throughout the coastal lagoon). The results show that reef cover increased in the last 24 years, and many neighbouring reefs have coalesced into large platforms. Growth rate varies spatially and temporally. Small reefs grow faster than large ones. Ficopomatus enigmaticus polychaetes living in higher salinity areas show a lower biomass than those living in brackish water areas, and the same pattern was observed for the inter-ring distance measured on the tubes. The results also show that important environmental variables, including salinity, nutrient availability and environmental energy (measured as current speed and depth) may be the most important factors a¡ecting the growth and spread of the reefs.

No abstract

RESUMENEn este trabajo se presentan los resultados de los análisis realizados sobre los materiales del sitio arqueológico Gruta de El Manzano, localizado sobre el río Grande, en el Departamento de Malargüe, al sur de la provincia de Mendoza. Utilizando la información generada, se discuten aspectos de la funcionalidad del sitio, los cambios a través del tiempo y se destaca su importancia para la discusión de los temas de la arqueología del norte de Patagonia. Los recientes fechados radiocarbónicos ubican al inicio de las ocupaciones en más de 8.000 años AP y confirman la existencia del hiatus regional para el holoceno medio. Los materiales analizados muestran importantes cambios en las tendencias de los mismos, especialmente hacia la segunda mitad del holoceno tardío, donde los diferentes indicadores sugieren diferencias en relación a la movilidad, el uso de la fauna, los recursos vegetales y la incorporación de tecnología cerámica.PALABRAS CLAVES: cazadores-recolectores, norte de Patagonia, Mendoza, tendencias temporales.ThE ARChAEOLOGICAL RECORD fROM GRUTA EL MANZANO AND ThEIR IMPLICANCES fOR NODPATAGONIA ARChAEOLOGY ABSTRACTIn this paper we present the results of the analysis carried out with the materials from Gruta de El Manzano archaeological site, located beside Grande River, in Malargüe, southern Mendoza province. Using the new information, we discuss the site function, changes trough time, and remark his importance for the northern Patagonia discussion. The last radiocarbon data place the beginning of the occupation in more than 8.000 years BP and confirm the existence of the mid holocene regional hiatus. The anali-* CONICET-Museo de historia Natural de San Rafael, Mendoza, Argentina. gustavoneme@arqueologiamendoza.org.

No abstract