Frank Schäbitz

Holocene climatic variations in northern Patagonia, Argentina

Abstract Seventeen playa lakes in Patagonia between 39° and 47° S were cored with the aim of reconstructing the vegetational, climatic and geomorphological history by means of sedimentological and palynological analysis. The paper discusses the initial results from two salt lakes, Salina Anzoategui (39°00′23′S, 63°46′30”W) and Salina Piedra (40°34′59”S, 62°40′26”W), lying in closed depressions at the northeastern margin of the arid diagonal of Patagonia. Both the sedimentological and the palynological results of the analyzed sediment cores from these playa lakes suggest prevailing arid climatic conditions with mainly aeolian morphodynamic processes during the mid-Holocene. In late Holocene times the climate changed to more semi-arid conditions, with a higher rainfall frequency and more frequent fluvial input into the lake, possibly reflecting greater influence from the Atlantic high pressure cell leading to more distinct seasonality.

New insights into paleoenvironmental changes in Laguna Potrok Aike, southern Patagonia, since the Late Pleistocene: The PASADO multiproxy record

A series of long sediment cores was retrieved from Laguna Potrok Aike, Southern Patagonia, within the framework of PASADO (Potrok Aike Maar Lake Sediment Archive Drilling Project), an ICDP (International Continental Scientific Drilling Program) lake drilling project. This maar lake, located at 52°S, 70°W in the Province of Santa Cruz (Argentina), in the southernmost continental area of the world, is one of the few permanent lakes in the region, providing a unique continuous paleoclimatic and paleoecological lacustrine record for the last glacial cycle. Previous multiproxy studies of this site have characterized the environmental history of these dry lands in the Patagonian Steppe for the last 16 cal. ka BP. This new series of sediment cores provides a much longer record of climate variability in Southern Patagonia since 51.3 cal. ka BP. Using a multiproxy strategy, a set of samples (mostly from core catcher material) was analyzed for physical properties, rock magnetism, geochemistry, CNS elemental analysis, stable isotopes, pollen and diatoms. This preliminary multiproxy limnogeological interpretation sheds new light on the regional Pleistocene and Holocene environmental history, revealing lake-level variations through time and identifying time windows of interest where higher resolution analyses will be carried out.

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.

Intensified Southern Hemisphere Westerlies regulated atmospheric CO2 during the last deglaciation

The causes for the rise of atmospheric CO 2 during the last deglaciation are complex and remain a matter of controversial scientific discussion. One hypothesis explains this phenomenon with CO 2 release from the deep ocean. A change in atmosphere-ocean interaction induced by a shift or intensification of Southern Hemisphere Westerlies (SHW) could have stimulated this process. Here this hypothesis is tested using oxygen isotope ratios of aquatic cellulose from Patagonian lacustrine sediments as west-wind proxy. Our record indicates maximum SHW strength at 52°S between 13.4 and 11.3 calibrated kyr B.P. This is in agreement with an increase in zonal wind strength extending to the southern mid-latitudes during the Younger Dryas chronozone triggering the final CO 2 increase. Comparison with other Southern Hemisphere records implies southward migration of strengthened SHW at that time, leading to interglacial CO 2 levels and hence terminating the Last Glacial.

Potential and limits of combining studies of coarse- and fine-grained sediments for the coastal event history of a Caribbean carbonate environment

Abstract The coastal deposits of Bonaire, Leeward Antilles, are among the most studied archives for extreme-wave events (EWEs) in the Caribbean. Here we present more than 400 electron spin resonance (ESR) and radiocarbon data on coarse-clast deposits from Bonaire’s eastern and western coasts. The chronological data are compared to the occurrence and age of fine-grained extreme-wave deposits detected in lagoons and floodplains. Both approaches are aimed at the identification of EWEs, the differentiation between extraordinary storms and tsunamis, improving reconstructions of the coastal evolution, and establishing a geochronological framework for the events. Although the combination of different methods and archives contributes to a better understanding of the interplay of coastal and archive-related processes, insufficient separation, superimposition or burying of coarse-clast deposits and restricted dating accuracy limit the use of both fine-grained and coarse-clast geoarchives to unravel decadal- to centennial-scale events. At several locations, distinct landforms are attributed to different coastal flooding events interpreted to be of tsunamigenic origin. Coastal landforms on the western coast have significantly been influenced by (sub)-recent hurricanes, indicating that formation of the coarse-clast deposits on the eastern coast is likely to be related to past events of higher energy. Supplementary material: The entire dataset of ESR and 14C dating results used in this paper is available at http://www.geolsoc.org.uk/SUP18637.

Palinología y Condiciones Paleoambientales Durante los últimos 12.600 Cal. Años ap en Salinas Del Bebedero (San Luis, Argentina)

Abstract. PALYNOLOGY AND PALEOENVIRONMENTAL CONDITIONS DURING THE LAST 12,600 CAL. YEARS BP AT SALINAS DEL BEBEDERO (SAN LUIS, ARGENTINA). The availability of late Quaternary paleoenvironmental information in central-western Argentina is still scarce because of the paucity of archives recording past environmental changes. This work reports palynological and sedimentological analyses of a sedimentary sequence from a core taken in the Salinas del Bebedero playa-lake basin (33°20′S-66°45′W), with the main objective of contributing towards the knowledge on vegetation and paleoenvironmental history in central western Argentina during the last c. 12,600 cal. yrs BP. Sedimentological results suggest a maximum lake high-stand c. 12,600 after which lake levels decreased until c. 3600 cal. yrs BP when modern lake levels were reached. Pollen analysis suggests a regional vegetation with Monte-Espinal affinity similar to the present-day vegetation, which essentially remained unchanged during the Holocene. Prior to that time, the predominance of halophytic communities around c. 12,600 cal. yrs BP suggests more arid conditions due to lower precipitation (and/or higher temperatures) compared with the present day conditions.

Pollen analysis for the generation of environmental hypothesis

Abstract Q-mode factor analysis combined with R- and Q-mode cluster analysis were used as hypothesis-generating tools on modern pollen dispersal data for Cerro Domuyo, Neuquen (Argentina). Q-mode cluster analysis partitioned the data matrix into three groups of samples that were consistent with plant geographic units (Subantartic forest, bogs, patagonian and andean xeric communities). Q-mode factor analysis produced three principal components that accounted fot 87% of the total variance and were assigned respectively to temperature, topographic gradient and precipitation. Three particular combinations of these components corresponded to the group of samples generated by Q-mode cluster analysis. When R-mode cluster analysed, each group of samples reflected a peculiar correlation of plant taxa. A model was postulated stating that the ‘causal’ structure of the system is the particular combination of those three physical components of the environmental complex and that the peculiar correlations of plant taxa ...

Vegetation response to climate forcing during the last glacial maximum and deglaciation in the East Carpathians: attenuated response to maximum cooling and increased biomass burning

The Carpathian Mountains were one of the main mountain reserves of the boreal and cool temperate flora during the Last Glacial Maximum (LGM) in East-Central Europe. Previous studies demonstrated late glacial vegetation dynamics in this area; however, our knowledge on the LGM vegetation composition is limited due to the scarcity of suitable sedimentary archives. Here we present a new record of vegetation, fire and lacustrine sedimentation from the youngest volcanic crater of the Carpathians (Lake St Anne, Lacul Sfânta Ana, Szent-Anna-to) to examine environmental change in this region during the LGM and the subsequent deglaciation. Our record indicates the persistence of boreal forest steppe vegetation ( Pinus sylvestris , Pinus mugo , Pinus cembra , Betula , Salix , Populus , Picea abies ) in the foreland and low mountain zone of the East Carpathians and Juniperus shrubland at higher elevation. We demonstrate attenuated response of the regional vegetation to maximum global cooling. Between ~22,870 and 19,150 cal yr BP we find increased regional biomass burning that is antagonistic with the global trend. Increased regional fire activity suggests extreme continentality likely with relatively warm and dry summers. We also demonstrate xerophytic steppe expansion directly after the LGM, from ~19,150 cal yr BP, and regional increase in boreal woodland cover with Pinus and Betula from 16,300 cal yr BP. Plant macrofossils indicate local (950 m a.s.l.) establishment of Betula nana and B . pubescens at 15,150 cal yr BP, Pinus sylvestris at 14,700 cal yr BP and Larix decidua at 12,870 cal yr BP. Pollen data furthermore hints at the regional presence of some temperate deciduous trees during the LGM ( Fagus sylvatica , Carpinus betulus , Corylus avellana , Fraxinus excelsior , Ulmus ). We also present pollen based quantitative climate reconstruction from this site and discuss its connection with other climate reconstructions and climate modeling results.