Aldo R. Prieto

Late Quaternary Vegetation and Climate of Patagonia

Publisher Summary This chapter focuses on the existing pollen datasets from Patagonia, between 37 o and 52 o S covering the Late Quaternary and a comparison with selected pollen data from Chile. A continuous pollen record does not exist in Patagonia that link the Last Glacial Maximum (LGM) with previous interglacial–glacial periods. The only pollen record that probably represents interglacial conditions about 430 ka (MIS 11) is that from Canadon El Mosquito, in southern Patagonia. During the Mid Holocene, the westerlies brought higher humidity to both the Andean zone and the southern extreme of Patagonia. Semiarid conditions in extra-Andean region suggest that the westerlies were less intense than present. An increase of aridity and temperature at the northeast Patagonia led to an arid climate and to the establishment of the Arid Diagonal during this time. In Patagonia, postglacial times were characterized by high fire frequency. Human impact, volcanism, and climate have been proposed to explain spatial and temporal variations of this fire frequency throughout different intervals.

Tendencias climáticas para los pastizales pampeanos durante el Pleistoceno tardío-Holoceno: estimaciones cuantitativas basadas en secuencias polínicas fósiles

Abstract. Climatic trends for the Pampa grasslands during the late Pleistocene-Holocene: quantitative estimations based on fossil pollen sequences. Pollen-climate calibration models for mean annual temperature (Tan), annual precipitation (Pan) and precipitation efficiency (EP) are presented for the Pampa grasslands region (33°–41°S and 56°–67°W). The Pan and EP models were optimal (r2boots =0,669 and 0,717; RMSEP;boots= 16%) to apply Modern Analog Technique and to obtain late Pleistocene-Holocene quantitative climatic estimations based on fossil pollen from two alluvial sequences. In the central Pampa grasslands, Pan and EP values were 100 to 200 mm lower than present ones during the late Pleistocene (16000-12000 yr cal BP). During the Pleistocene-Holocene transition, early Holocene and late Holocene the values were similar to modem ones. In the southwest, Pan and EP values were c. 200 mm higher than present ones during the mid-Holocene (5500-3000 yr cal BP), and decreased during the late Holocene reaching similar modern values during the last 500 years cal. The climatic inferences agree with previous paleoclimatic interpretations that state dry to semiarid conditions during the late Pleistocene, and subhumid humid conditions during the Pleistocene-Holocene transition and early Holocene. However, there are discrepancies as from 5000 yr cal BP, probably related to the different sensitivity of the climate proxy data. The NE-SW precipitation gradient during the last c. 5500 yr cal may have been steeper than at present. These estimations are the first quantitative climatic reconstructions for the Pampa grasslands region, and should be taken as trends until new reconstructions confirm them.

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

Abstract 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.

LA PALEONTOLOGÍA EN ARGENTINA ENTRE 1908 Y 1912. UNA MIRADA DIFERENTE DESDE MAR DEL PLATA

Resumen . Se analiza el panorama paleontologico en Argentina y el rol que tuvieron las politicas estatales y privadas en los ambitos donde se desarrollaba la investigacion paleontologica en relacion con las politicas sociales entre 1908 y 1912. Este periodo se extiende desde la propuesta de construccion hasta la inauguracion oficial del Asilo Saturnino E. Unzue en Mar del Plata. Se utilizan como ejemplo y se comparan dos instituciones estatales, el Museo Nacional de Buenos Aires y la Sociedad de Beneficencia de la Capital y sus protagonistas que convergieron en la difusa frontera entre lo publico y lo privado, para analizar el rol del Estado en relacion con la Paleontologia y con la asistencia publica. Se discuten las diferencias entre “beneficencia” y “filantropia” en comparacion con lo que ocurria en Estados Unidos de America durante ese periodo. El Asilo Unzue se presenta como un ejemplo del interes de las clases altas de Argentina en realizar obras de beneficencia, en lugar de suplementar los fondos del erario publico para la construccion de museos o de ampliar las colecciones paleontologicas. Durante el periodo 1908-1912 los unicos representantes argentinos en las disciplinas paleontologicas fueron Florentino Ameghino y Francisco P. Moreno. Este periodo significo el final de la Paleontologia como se habia desarrollado desde la decada de 1880. La ausencia de discipulos en todas las disciplinas paleontologicas y la prematura muerte de Ameghino conspiraron para que recien bien entrado el siglo XX se iniciara una etapa floreciente en la Paleontologia. PALABRAS CLAVE. Paleontologia. Museo Nacional de Buenos Aires. Sociedad de Beneficencia de la Capital. Asilo Unzue. Florentino Ameghino. Argentina. Abstract. PALEONTOLOGY IN ARGENTINA BETWEEN 1908 AND 1912. A DIFFERENT POINT OF VIEW FROM MAR DEL PLATA. The paleontological framework and the role of the government and private policies in the area, where paleontological investigations were developed, are examined in relation to the social policies carried out in Argentina between 1908 and 1912. This period extends from the construction proposal until the official inauguration of the Asylum Saturnino E. Unzue in Mar del Plata. Two government institutions and their protagonists –the National Museum of Buenos Aires and the Charitable Society of the Capital– which converged on the fuzzy boundary between the public and private sectors, are used as examples and compared to analyze the role of the State in relation to Paleontology and the social policy. The difference between “charity” and “philanthropy” compared with what happened in the USA at that time is also discussed. The Asylum Unzue is presented as an example of how the patronage of the upper classes in Argentina was oriented toward charity works instead of supplementing the public treasury funds to build museums or enlarging paleontological collections. During the period from 1908 to1912, Florentino Ameghino and Francisco P. Moreno were the only Argentine representatives of the paleontological disciplines. This period marked the end of Paleontology as it had developed since1880 in Argentina. The absence of disciples in all paleontological disciplines together with the premature death of Ameghino erased the field from Argentine research until well into the twentieth century, when it began to flourish anew. KEY WORDS. Paleontology. National Museum of Buenos Aires. Charitable Society of Buenos Aires. Asylum Unzue. Florentino Ameghino. Argentina.