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One of the fundamental problems to quantifying past impact of anthropogenic activities is that long series of observational data for pollutant deposition and changes in the nutrient cycling of ecosystems (eutrophication) are often not available. Lake sediments may provide suitable archives to decipher the history of local and regional pollution and eutrophication. Here we provide quantitative high-resolution data for the history of airborne pollutants and eutrophication from sediments of five lakes in Central Chile between ca. AD 1800–2005. We use spheroidal carbonaceous particles (SCPs) from fossil fuel combustion and excess atmospheric Cu deposition from mining activities as a proxy for atmospheric deposition. Organic carbon and nitrogen flux rates to the sediments and C/N ratios are used as a proxy for aquatic primary production and eutrophication. We show that the lake sediment SCP and Cu records are highly consistent and depict in great detail the local and regional history of urban, industrial and transportation history as reported in independent documentary sources and statistics. The pre-industrial and pre-1950 background concentrations (and flux rates) of the substances can be quantified. We can also show that technical measures taken in the early 1980s to trim down Cu emissions from the copper mines reduced the excess atmospheric Cu fallout to the lakes by about 50%. Eutrophication of the lakes did not start before ca. 1980. Prior to that time, warm season temperatures explain most of the variance in TOC and N flux to the sediments. The three dimictic lakes show only moderate eutrophication responses to enhanced N supply (as atmospheric fallout; enrichment factors for TOC and N 1.1–2.6), suggesting that mainly phosphorus controls aquatic primary production. The meromictic lake, where phosphorus recycling is likely, shows the largest response (enrichment factors for TOC and N between 9–20). While all five lakes show overall consistent and similar trends for the pollution history during the 19th and 20th century, there are significant differences in the details of the individual profiles. This suggests that local sources are highly important and the common regional (background) signal is relatively marginal. This is very different from Europe.

A glacier–climate model was used to calculate climatic conditions in a test site on the east Andean slope around Cochabamba (17°S, Bolivia) for the time of the maximum Late Pleistocene glaciation. Results suggest a massive temperature reduction of about − 6.4 °C (+ 1.4/− 1.3 °C), combined with annual precipitation rates of about 1100 mm (+ 570 mm/− 280 mm). This implies no major change in annual precipitation compared with today. Summer precipitation was the source for the humidity in the past, as is the case today. This climate scenario argues for a maximum advance of the paleo-glaciers in the eastern cordillera during the global Last Glacial Maximum (LGM, 20 ka BP), which is confirmed by exposure age dates. In a synthesized view over the central Andes, the results point to an increased summer precipitation-driven Late Glacial (15–10 ka BP) maximum advance in the western part of the Altiplano (18°S–23°S), a temperature-driven maximum advance during full glacial times (LGM) in the eastern cordillera, and a pre- and post-LGM (32 ka BP/14 ka BP) maximum advance around 30°S related to increased precipitation and reduced temperature on the western slope of the Andes. The results indicate the importance of understanding the seasonality and details of the mass balance–climate interaction in order to disentangle drivers for the observed regionally asynchronous past glaciations in the central Andes.

A quantitative high-resolution autumn (September–November) temperature reconstruction for the southeastern Swiss Alps back to AD 1580 is presented here. We used the annually resolved biogenic silica (diatoms) flux derived from the accurately dated and annually sampled sediments of Lake Silvaplana (46°27′N, 9°48′E, 1800 m a.s.l.). The biogenic silica flux smoothed by means of a 9-yr running mean was calibrated (r=0.70, p

We found a significant positive correlation between local summer air temperature (May-September) and the annual sediment mass accumulation rate (MAR) in Lake Silvaplana (46°N, 9°E, 1800 m a.s.l.) during the twentieth century (r = 0.69, p < 0.001 for decadal smoothed series). Sediment trap data (2001-2005) confirm this relation with exceptionally high particle yields during the hottest summer of the last 140 years in 2003. On this base we developed a decadal-scale summer temperature reconstruction back to AD 1580. Surprisingly, the comparison of our reconstruction with two other independent regional summer temperature reconstructions (based on tree-rings and documentary data) revealed a significant negative correlation for the pre-1900 data (ie, late ‘Little Ice Age’). This demonstrates that the correlation between MAR and summer temperature is not stable in time and the actualistic principle does not apply in this case. We suggest that different climatic regimes (modern/‘Little Ice Age’) lead to changing state conditions in the catchment and thus to considerably different sediment transport mechanisms. Therefore, we calibrated our MAR data with gridded early instrumental temperature series from AD 1760-1880 (r = -0.48, p < 0.01 for decadal smoothed series) to properly reconstruct the late LIA climatic conditions. We found exceptionally low temperatures between AD 1580 and 1610 (0.75°C below twentieth-century mean) and during the late Maunder Minimum from AD 1680 to 1710 (0.5°C below twentieth-century mean). In general, summer temperatures did not experience major negative departures from the twentieth-century mean during the late ‘Little Ice Age’. This compares well with the two existing independent regional reconstructions suggesting that the LIA in the Alps was mainly a phenomenon of the cold season.

The recent warming of the global climate is well recognized. However, does a warmer climate also mean a moister climate? Does dry get drier and wet get wetter? There are important questions as they relate to changes in the water cycle and impacts the water resources as well as the frequency and intensity of storms and floods in the near future. In Europe, regional climate models do not show consistent and robust results for future hydroclimatic changes and how extreme events will evolve in response to future climate change. Paleo-hydroclimatic data from natural archives are one of the few means to assess such changes in the longer context. Here, we present an annually-resolved record of warm season (MJJA) precipitation and summer flood frequency from the varved (annually laminated) sediments of proglacial Lake Oeschinen (46°30′N–7°44′E, 1580 m, NW Swiss Alps) back to AD 884. These data sets are inferred from the thickness of annual sediment deposits and the occurrence of flood event layers in the sediments. The chronology of the sediment record is based on multiple varve counts and validated with historical floods chronicled in written documents (back to the 14th century) and 14C AMS dates. The precipitation record shows pronounced interannual to centennial variability with humid warm season phases between AD 920–950, AD 1100–1180, AD 1300–1400, AD 1590–1650, AD 1700–1790, AD 1820–1880, and AD 1960–2008. Driest conditions are reconstructed for AD 960–1080, AD 1250–1300 and for AD 1880–1900. Our precipitation record is consistent with the few multi-centennial warm-season precipitation records available for Europe. We did not find a persistent relationship between warm-season precipitation and temperature. In contrast, results show that the relation between precipitation and temperature has oscillated between positive correlations (warmer gets wetter, cooler gets drier) and negative correlations (warmer gets drier, cooler gets wetter) with a highly significant (χ2 = 99%) multidecadal (60–70 yrs) periodicity over the last millennium. Possible explanations for this phenomenon are changes in the weather type statistics or the within-weather-type variability, which influence the combinations between precipitation and temperature over continental central Europe and operate at multidecadal scales. Such multidecadal effects might also be important for precipitation scenarios in the Alpine area under future warming. Our record of flood frequency suggests more frequent floods under cool and humid climate during the warm seasons. This picture is consistent with other studies from small and medium size catchments at mid- and high elevations in the Alpine area. However, the 13th century reveals a period with high flood frequency during warm and moderately dry (average precipitation) conditions. This anomalous situation is currently not understood; nonetheless, this is also one out of several possible scenarios for the future. From the different combinations found in our record, we conclude that the relation between floods, precipitation and temperature and, in consequence, future projections remain poorly constrained.

Reconstructions of paleoclimatic and paleoenvironmental data from sediment records require a thorough knowledge of the physical, chemical and biological factors that influence sediment-formation processes and signal preservation in lake sediments. Lake Żabińskie, an eutrophic hardwater lake located in northeastern Poland (Masurian Lake District), provides an unique environment for the investigation of processes that lead to the varve formation. During a two-year long observation period we investigated limnological and hydrochemical conditions within the water column, recent sediment fluxes and laminations preserved in the sediments of this lake to understand the relationship between the lake water properties and the sediment formation processes. We demonstrate that different mixing patterns may occur in Lake Żabińskie, from dimictic to meromictic depending on the meteorological conditions. Regardless of the water mixing pattern, the lake was stratified during much of the year which led to significant differences between surface and near-bottom water environments. The hypolimnion was characterized by higher conductivity and anoxic conditions with only short periods of better oxygenation, which created conditions ideal for the formation and preservation of biogenic varves. The material collected from the sediment trap revealed notable changes in sediment fluxes with characteristic spring maxima and, optionally, a second late fall maxima. Considerable variability was also observed for the fluxes of total organic carbon, biogenic silica and calcite. Microscopic investigation of the topmost sediments revealed a complex structure of the varves showing a distinct spring calcite lamina followed by several fine calcite laminae interbedded with diatom-rich laminae and, finally, by an organic-rich lamina with minerogenic admixtures deposited during winter. This seasonal variability was also reflected in the chemical composition inferred from high-resolution XRF measurements which allowed for the recognition of individual seasons within one varve. A characteristic annual succession of elemental composition followed a distinct pattern: spring was marked with a silica peak followed by a major calcium peak; during summer and fall minor calcium peaks occurred as well as maxima in iron and sulphur; winter was characterized by a peak in potassium. This study shows a remarkable potential of the sediment record from Lake Żabińskie as a high-resolution paleoenvironmental archive.

Varved lake sediments from Lake Zabihskie (northeastern Poland) provide a high- resolution calendar-year chronology which allows validation of 14C dating results. Microscopic analy­sis of the varve microfacies revealed that laminations found in Lake Zabihskie were biogenic (calcite) varves. Three independent counts indicated a good preservation quality of laminae in the 348 cm long sediment profile which contained 1000+12/-24 varves. The varve chronology was validated with the 137Cs activity peaks, the tephra horizon from the Askja eruption at AD 1875 and with the timing of major land-use changes of known age inferred from pollen analysis. 32 AMS 14C dates of terrestrial macrofossils distributed along the profile were compared with the varve chronology. After identifica­tion of outliers, the free-shape model performed with 21 14C dates provided the best possible fit with the varve chronology. We observed almost ideal consistency between both chronologies from the present until AD 1250 while in the lower part (AD 1000-1250) the difference increases to ca. 25 years. We demonstrate that this offset can be explained by too old radiocarbon ages of plant remains trans­ported to the lake by the inflowing creek. Results of this study highlight that careful interpretation of radiocarbon age-depth models is necessary, especially in lakes where no annual laminations are ob­served and no independent method are used for cross-validation.

210Pb, 137Cs and 14C dated sediments of two late Holocene landslide lakes in the Provincial Park Lagunas de Yala (Laguna Rodeo, Laguna Comedero, 24°06′S, 65°30′W, 2100 m asl, northwestern Argentina) reveal a high-resolution multi-proxy data set of climate change and human impact for the past ca. 2000 years. Comparison of the lake sediment data set for the 20th century (sediment mass accumulation rates MARs, pollen spectra, nutrient and charcoal fluxes) with independent dendroecological data from the catchment (fire scars, tree growth) and long regional precipitation series (from 1934 onwards) show that (1) the lake sediment data set is internally highly consistent and compares well with independent data sets, (2) the chronology of the sediment is reliable, (3) large fires (1940s, 1983/1984-1989) as documented in the local fire scar frequency are recorded in the charcoal flux to the lake sediments and coincide with low wet-season precipitation rates (e.g., 1940s, 1983/1984) and/or high interannual precipitation variability (late 1940s), and (4) the regional increase in precipitation after 1970 is recorded in an increase in the MARs (L. Rodeo from 100 to 390 mg cm-2 yr-1) and in an increase in fern spores reflecting wet vegetation. The most significant change in MARs and nutrient fluxes (Corg and P) of the past 2000 years is observed with the transition from the Inca Empire to the Spanish Conquest around 1600 AD. Compared with the pre-17th century conditions, MARs increased by a factor of ca. 5 to >8 (to 800 +130, -280 mg cm-2 yr-1), PO4 fluxes increased by a factor of 7, and Corg fluxes by a factor of 10.5 for the time between 1640 and 1930 AD. 17th to 19th century MARs and nutrient fluxes also exceed 20th century values. Excess Pb deposition as indicated by a significant increase in Pb/Zr and Pb/Rb ratios in the sediments after the 1950s coincides with a rapid expansion of the regional mining industry. Excess Pb is interpreted as atmospheric deposition and direct human impact due to Pb smelting. © 2006 Elsevier Ltd and INQUA. Fil: Lupo, Liliana Concepcio. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Jujuy; Argentina Fil: Bianchi, Maria Martha. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional del Comahue; Argentina Fil: Aráoz, Ezequiel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Laboratorio de Investigaciones Ecológicas de las Yungas; Argentina Fil: Grau, Hector Ricardo. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Laboratorio de Investigaciones Ecológicas de las Yungas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Lucas, Christoph. University of Bern; Suiza Fil: Kern, Raoul. University of Bern; Suiza Fil: Camacho, María. Universidad Nacional de Jujuy; Argentina Fil: Tanner, Willi. University of Bern; Suiza Fil: Grosjean, Martin. University of Bern; Suiza

Eclogae Geologicae Helvetiae, 98 (3), ISSN:0012-9402, ISSN:1420-9128

Palaeoindian occupation of the Atacama Desert in northern Chile has been found between 12 600 and 10 200 cal. yr BP. The new site at Salar Punta Negra (24°28′S/60°53′W/2976 m) includes about 1000 classifiable, mostly unifacial artefacts and, uniquely, three different diagnostic types of early projectile points. Two of the Lateglacial/early Holocene projectile types have wide distribution and are known from different geographical areas in South America: the Palaeoindian ‘Fell’ fish-tail point mainly from the southern cone of South America, and the triangular ‘Tuina’ points typical of the Puna of the south-central Andes in northern Chile and northwestern Argentina. In addition, we found a third type, a stemmed point typical for the Salar Punta Negra. Filling a large geographical gap of ‘Fell’ occupation, the site at Salar Punta Negra provides evidence for generally much higher mobility and diversity of early cultures, and supports an Andean-Pacific route for early human exploration of South America to the south through the desert at intermediate altitudes. Contemporaneous high-amplitude climatic changes were fundamental preconditions to provide adequate environments and habitats, and to make Palaeoindian hunting-gathering occupation possible in the Atacama Desert. Copyright © 2005 John Wiley & Sons, Ltd.

The question whether the mid-Holocene climate (between ca. 9 and 4 cal kyr B.P.) in the Atacama Desert and the Central Andes in general was humid or dry has wide implications with regard to the understanding of long-term climate variability in South America. Paleosols, regional groundwater tables, abiotic proxy data and pollen of aquatic plants in lake sediments show a marked and rapid shift from very humid late-glacial/early Holocene climatic conditions (between ca. 14 and 9.5 kyr B.P.) to extremely dry mid-Holocene conditions (more arid than today between ca. 9 and 4 kyr B.P.). An exception during this hyperarid period is a century-scale more humid interval around ca. 5.5–6 kyr B.P. that appears systematically in lake sediment archives. In contrast, pollen for most terrestrial plants preserved in lake sediments do not show major changes during the Holocene, whereas more humid mid-Holocene conditions (compared with late Holocene conditions) were inferred from plant macrofossils in rodent middens. Is the reason for this disagreement to be attributed to misinterpretation of the paleoenvironments or of the proxy records themselves, or to incomplete paleoclimatic interpretation of the paleoenvironments? We argue that these different paleoclimate archives record different aspects and facets of ‘climate’. While paleosols and groundwater in the Atacama Desert record low-frequency climate variability at century to millennium scales, lake sediments on the Altiplano record decade- to century-scale variability. Terrestrial vegetation responds to shorter high-frequency climate variability at seasonal to inter-annual scales and preferably to humid years. Vegetation remains in ‘hibernation’ or does not germinate during arid years. Thus information from these three types of archives is not a priori comparable and requires careful site-specific, archive-specific and time-scale-specific evaluation. What is natural in modern climatology is also true for paleoclimatology: a comprehensive assessment must account for the complex daily and seasonal cycles, for the range of climate variability and trends at different scales in space and time, for impacts of short-term extreme events, and for specific, often non-linear responses of individual bio-geo-physical archives to any of the numerous aspects of ‘climate’.

This special issue of Climatic Change contains a series of research and review articles, arising from papers that were presented and discussed at a workshop held in Davos, Switzerland on 25–28 June 2001. The workshop was titled ‘Climate Change at High Elevation Sites: Emerging Impacts’, and was convened to reprise an earlier conference on the same subject that was held in Wengen, Switzerland in 1995 (Diaz et al., 1997). The Davos meeting had as its main goals, a discussion of the following key issues: (1) reviewing recent climatic trends in high elevation regions of the world, (2) assessing the reliability of various biological indicators as indicators of climatic change, and (3) assessing whether physical impacts of climatic change in high elevation areas are becoming evident, and to discuss a range of monitoring strategies needed to observe and to understand the nature of any changes.

A climate glacier model is used to interpret late Pleistocene maximum glaciations in the NW-Argentinan Andes (22°S). According to the model, massive cooling combined with a moderate precipitation increase is necessary to explain maximum glacier extension. Even given a factor of 2–4 precipitation increase, the model indicates that temperatures must have been lowered by 4.5–8°C, suggesting that maximum glaciation probably occurred during full glacial times of MIS 2 (25–18 ka). This conclusion is supported by dated proglacial lake sediments and evidence of past glacial geometry. The extremely long tongues and low accumulation area ratios indicate that ablation was reduced during cold periods in agreement with the model. A strong relationship exists between glacier geometry and prevailing climate. Contrary to the precipitation-controlled Late Glacial (12–10 ka) maximum glaciation of the arid Central Andes in southern Peru and northern Chile, the glaciations on the much more humid eastern Andean slope are mainly controlled by temperature and therefore reached their maximum extent during the MIS 2 cold conditions.

An empirical-statistical climate-glacier model is used to reconstruct Late Pleistocene climate conditions in the south-central Andes of northern Chile (29–30° S). The model was tested using modern climate data and the results compare favorably with key glaciological features presentlyobserved in this area. Using several glaciers at 29° S as casestudies, the results suggest an increase in annual precipitation(Δ P = 580 ± 150 mm, today 400 mm), and a reduction inannual mean temperature (Δ T = −5.7 ± 0.7 ° C).These data suggest full glacial LGM (Last Glacial Maximum) conditionsfor the maximum glacier advances at 29° S, a scenario that is asynchronous with the timing of maximum advances north of the Arid Diagonal (18–24° S) where late-glacial climate was moderately cold but very humid.The reconstructed case study glaciers at 29° S do not allow conclusions to be drawn about the seasonality of precipitation. However, comparison with regional paleodata suggests intensified westerly winter precipitation and a stable position for the northern boundary of the westerlies at ∼ 27° S. However, the meridional precipitation gradients were much steeper than today while the core area of the Arid Diagonal remained fixed between 25–27° S.

Treelines are expected to rise to higher elevations with climate warming; the rate and extent however are still largely unknown. Here we present the first multi-proxy palaeoecological study from the treeline in the Northwestern Swiss Alps that covers the entire Holocene. We reconstructed climate, fire and vegetation dynamics at Iffigsee, an alpine lake at 2,065 m a.s.l., by using seismic sedimentary surveys, loss on ignition, visible spectrum reflectance spectroscopy, pollen, spore, macrofossil and charcoal analyses. Afforestation with Larix decidua and tree Betula (probably B. pendula) started at ~9,800 cal. b.p., more than 1,000 years later than at similar elevations in the Central and Southern Alps, indicating cooler temperatures and/or a high seasonality. Highest biomass production and forest position of ~2,100–2,300 m a.s.l. are inferred during the Holocene Thermal Maximum from 7,000 to 5,000 cal. b.p. With the onset of pastoralism and transhumance at 6,800–6,500 cal. b.p., human impact became an important factor in the vegetation dynamics at Iffigsee. This early evidence of pastoralism is documented by the presence of grazing indicators (pollen, spores), as well as a wealth of archaeological finds at the nearby mountain pass of Schnidejoch. Human and fire impact during the Neolithic and Bronze Ages led to the establishment of pastures and facilitated the expansion of Picea abies and Alnus viridis. We expect that in mountain areas with land abandonment, the treeline will react quickly to future climate warming by shifting to higher elevations, causing drastic changes in species distribution and composition as well as severe biodiversity losses., Vegetation History and Archaeobotany, 23 (5), ISSN:1617-6278, ISSN:0939-6314

Climate change is clearly discernible in observed climate records in Switzerland. It impacts on natural systems, ecosystems, and economic sectors such as agriculture, tourism, and energy, and it affects Swiss livelihood in various ways. The observed and projected changes call for a response from the political system, which in Switzerland is characterized by federalism and direct democratic instruments. Swiss climate science embraces natural and social sciences and builds on institutionalized links between researchers, public, and private stakeholders. In this article, we review the physical, institutional, and political aspects of climate change in Switzerland. We show how the current state of Swiss climate science and policy developed over the past 20 years in the context of international developments and national responses. Specific to Switzerland is its topographic setting with mountain regions and lowlands on both sides of the Alpine ridge, which makes climate change clearly apparent and for some aspects (tourist sector, hydropower, and extreme events) highly relevant and better perceivable (e.g., retreating glaciers). Not surprisingly the Alpine region is of central interest in Swiss climate change studies.

Lake sediments and pollen, spores and algae from the high-elevation endorheic Laguna Miscanti (22°45′S, 67°45′W, 4140 m a.s.l., 13.5 km2 water surface, 10 m deep) in the Atacama Desert of northern Chile provide information about abrupt and high amplitude changes in effective moisture. Although the lack of terrestrial organic macrofossils and the presence of a significant 14C reservoir effect make radiocarbon dating of lake sediments very difficult, we propose the following palaeoenvironmental history. An initial shallow freshwater lake (ca. 22,000 14C years BP) disappeared during the extremely dry conditions of the Last Glacial Maximum (LGM; 18,000 14C years BP). That section is devoid of pollen. The late-glacial lake transgression started around 12,000 14C years BP, peaked in two phases between ca. 11,000 and

At this critical moment of Earth’s history, as we move from a century with rapidly growing human impacts on all the different ecosystems of our planet, to a century with a probable further acceleration in the pace of environmental change, resource use, and vulnerability for societies and economies, we have to rethink the changing relationship between nature and human beings from the past, through the present, towards a future full of uncertainty. It becomes more and more evident that major natural processes from the local to the global level are influenced by human activities, creating a much higher degree of complexity through the interaction of processes which are within the domain of both the natural and social sciences. This implies a need to bridge the gulf between the two cultures of science in order to advance our understanding of contemporary driving forces and their rapidly growing impact on earth’s ecosystems. “The biggest changes happened in our century, more precisely in the last 50 years, with a rate unknown before in Earth’s history” (Pfister 1995a). In light of continued population growth, economic development, urbanisation, industrialisation and resource use, it is clear that human impacts on ecosystems world-wide will continue to increase in the next century.

A climate–glacier model was used to reconstruct Late-glacial climate conditions from two case-study glaciers at 18° and 22° S in the arid (sub)tropical western Andes of northern Chile. The model uses (i) the geometry of the Late-glacial maximum glaciation, (ii) modern diurnal and annual cycles, amplitudes and lapse rates of the climate, (iii) empirical–statistical sublimation, melt and accumulation models developed for this area, and (iv) dynamic ice flow through two known cross-sections for steady-state conditions. The model is validated with modern conditions and compares favorably with the glaciological features of today. The mass-balance model calculates the modern equilibrium-line altitude at 18° S as high as 5850 m (field data 5800 m), whereas no glaciers exist in the fully arid southern area at 22° S despite altitudes above 6000 m and continuous permafrost. For Late-glacial times, the model results suggest a substantial increase in tropical summer precipitation (ΔP = +840 (− 50/+ 10) mm a−1 for the northern test area; +1000 (− 10/+ 30) mm a−1 for the southern test area) and a moderate temperature depression (ΔT = −4.4 (− 0.1/+ 0.2) °C at 18° S; −3.2 (±0.1) °C at 22° S). Extratropical frontal winter precipitation (June–September) was

We investigate the Holocene sedimentary infilling of two high-altitude (>4000 m a.s.l.) lacustrine basins in the subtropical regions of the Atacama Altiplano (Central Andes, northern Chile) that today contain permanent, shallow saline lakes: Laguna del Negro Francisco (27°S) and Laguna Miscanti (23°S). Laguna Miscanti was surveyed with multi-frequency, high-resolution seismic techniques and sediment cores were retrieved from offshore areas of both lakes. Because of the geological location of these lacustrine basins within the active Andean convergent margin, and the presence of present and past climatic gradients in the Altiplano, our detailed sedimentologic, mineralogic and geochemical study evaluates tectonic, volcanic, and climatic controls on lacustrine sedimentation in an arid environment. Both lakes originated by tectonic and volcanic activity during the Pleistocene. Tectonic control of basin dynamics was clearly exerted during the early stages: increased subsidence was responsible for alluvial fan activity in the Laguna Miscanti Basin prior to the establishment of the lake, and the Negro Francisco Basin changed from exorheic to endorheic. Hydrogeologic conditions needed to maintain the two perennial saline lakes are largely controlled by the basins' tectonic history. The evolution of Laguna del Negro Francisco comprises four successive stages: (1) perennial saline carbonate–sulfate lake; (2) saline pan–saline lake complex with a carbonate–sulfate brine; (3) a perennial brackish stage with high macrophyte (Chara) productivity and mostly calcite formation; and (4) a residual stage with halite precipitation. The depositional history recorded in the Miscanti core illustrates the evolution from an aragonite-producing, ephemeral saline lake to a macrophyte-dominated perennial brackish lake, with an aragonite saline pan–saline lake complex and a calcite-producing perennial brackish lake as intermediate stages. The hydrologic budget of the lakes is a direct response to effective moisture (precipitation–evaporation) fluctuations and, therefore, climate variability has played a major role in chemical composition and lake level changes. Climate forcing has controlled the depositional history of the lakes during the Holocene. Our study illustrates different responses of lake systems to external climatic forcing, especially with respect to cyclicity, threshold dynamics and the importance of sedimentary recycling. The main sedimentary sequences in both lakes correspond to cycles of increasing and decreasing effective moisture. However, this cyclicity is characterized by abrupt change rather than gradual evolution. Threshold dynamics modulated limnogeological changes and caused a stepwise evolution of the lacustrine systems. Laguna Miscanti and Laguna del Negro Francisco sedimentary sequences provide depositional models for small, topographically closed, brackish to saline lakes that developed on active margins and evolved under fluctuating but generally arid climatic conditions.

Se demuestra que los eventos aridos del Holoceno Medio y los cambios paleoambientales fueron sincronicos con transformaciones culturales y tecnologicas tales como la diversificacion de la industria litica, emergencia de arquitectura compleja, cambio en el uso de rocas, actividades semipermanentes y coexistencia de domesticacion de camelidos con practicas de caza–recoleccion (4.050-4.800 A.P). Se identifica el desarrollo de agricultura, pastoralismo pleno y uso de ceramica despues de los 3.200 anos A.P, a traves de las fases del Complejo Cultural San Pedro de Atacama con restos prehispanicos e histricos incluyendo las practicas de ganadera trashumantica contemporanea. Finalmente se describe el Intervalo Arido en relacion a su extension geografica circumpunena.AbstractWe show that mid-Holocene arid events and paleoenvironmental changes were synchronous with cultural and technological changes such as lithic industry diversification, emerging o f a complex architecture, changes in the use of rocks, semipermanent activity, and the coexistence between camelids domestication and hunter and gathers practices (4.050-4.800 B .P). After 3.200 BP agricultural and complex pastoralism sequence begin with a new ceramic and architectural pattern. Thought San Pedro de Atacama main phases in prehispanic complex and hispanic influences includes herder practice and contemporany trashumance. Arid Interval at a macrospace level of the Circumpuna surroundings is also described.

Late Quaternary humidity changes resulted in substantial modifications of the land surface characteristics in the Altiplano of the Atacama Desert, central Andes. Reconstructions of surface albedo, top-of-atmosphere (TOA) albedo, and short-wave net radiation in the Andes of northern Chile for 20, 14, 10, 7 and 0 ka suggest that surface and TOA albedo increased substantially during periods of relatively humid environmental conditions (i.e., with large palaeolakes, glaciers and dense vegetation). The decrease of summer shortwave net radiation and seasonality during the late-glacial/early Holocene humid phase (14 to 10 ka) due to Earth’s surface and atmospheric characteristics added to the effect of orbitally driven negative deviations of Southern Hemisphere austral summer insolation and minimum seasonality at 20 °S. Therefore, in situ radiative forcing is, in contrast to the Northern Hemisphere tropics, not a suitable explanation for enhanced convective precipitation and, ultimately, humid climatic conditions. Our results suggest that late Quaternary humidity changes on the Altiplano reflect a collective response to (1) environmental changes in the source area of the moisture (e.g., re-expansion of the rain forest and increased release of latent heat over Amazonia and the Chaco, warm sea surface temperatures in the E Pacific) and, (2) large-scale circulation patterns and wave structures in the upper troposphere (strength and position of the Bolivian High, divergent flow stimulating convection over the Altiplano), or that they even reflect a response to (3) interhemispherical teleconnections.

Radiocarbon dates and relative ages of soils on moraines provide evidence of a substantial late-Holocene (

Twenty archaeological campsites intercalated between more than 30 debris flows caused by heavy rainfall events between 6200 and 3100 14C yr B.P. have recently been discovered at Quebrada Puripica in the Atacama Desert of northern Chile. This record provides detailed information about extreme, short-lived climatic events during the hyperarid mid-Holocene period. For the first time, we found evidence of continuous human occupation in this area, filling the regional hiatus in the Atacama basin (“Silencio Arqueologico”) between 8000 and 4800 14C yr B.P. The transformation of Early Archaic hunters into the complex Late Archaic cultural tradition was an adaptive process. During this time, the site was a local ecological refuge with abundant resources in a generally hostile environment.

Lacustrine sediments from the high elevation, endorheic, saline lake Negro Francisco (27°28'S/69°14'W, 4125 m) provide a detailed mid- and late-Holocene environmental history of the Southern Chilean Altiplano. Mineralogy, chemical composition and sedimentary facies analyses of the deposits confirm the regional significance of mid-Holocene aridity between 6000 and 3800 BP. Precipitation rates were signifi cantly lower than the c. 250 mm yr-1 of today. Fully arid conditions were interrupted by short-term moist spells with an average return period of about 200 years. Effective moisture increased after 3800 BP and peaked between 3000 and 2600 BP and between 2200 and 1800 BP in two phases with conditions more humid than today. Comparison with regional palaeodata suggest that these two late-Holocene humid spells were most likely related to Pacific moisture sources. Salinity levels increased again in Laguna del Negro Francisco after 1800 BP. The onset of modern climatic conditions was a stepwise, nonlinear process. However, the functioning of modern climate in this remote part of the world is not understood well enough to explain fully possible mech anisms of climatic changes in the past.

Conventional radiocarbon dates for sediment samples from aquatic systems and of coeval terrestrial samples deviate from each other due to the reservoir effect. The reservoir correction is usually assumed to be constant with time for a specific aquatic system. Our studies confirm that seasonal and secular changes are frequent and are governed by the limnological conditions. Lakes have two principal sources of14C: atmospheric CO2and the total dissolved inorganic carbon (TDIC) of the entering groundwater and runoff. The former has values ofca.100 pMC; the latter usually has a14C value well below 100 pMC. Atmospheric CO2enters the lake by exchangeviaits surface. The proportions of these two kinds of input determine the magnitude of the reservoir correction in freshwater lakes. It is mainly a function of the volume/surface ratio of the lake and, consequently a function of the water depth. The surface of lakes with outflow does not change when sedimentation decreases the depth of the water. The depth of Schleinsee Lake in southern Germany has decreased from 30 to 15 m sinceca.9000 bp. As a result, the reservoir correction has decreased fromca.-1550 to -580 yr. In contrast, the depth of Lake Proscansko in Croatia increased with growth of the travertine dam and the reservoir correction changed fromca.-1790 to -2650 yr during the last 8800 yr. The largest fluctuations of lake levels occur in closed lakes in arid regions when the climate changes from humid to arid andvice versa.As a result, the reservoir correction of the14C dates for the total organic fraction from Lejía Lake in the Atacama Desert of Chile varied between 14C dating of lake sediments requires a study of the temporal changes of the reservoir effect by analysis of both the organic and marl fractions. The most reliable14C dates are obtained from terrestrial plant remains.

Estudios multidisciplinarios han permitido reconstruir los cambios extremos en el balance hidrico experimentados en la Puna de Atacama durante el Holoceno. La intensificacion del monzon de verano (invierno boliviano) aumento la precipitacion de origen continental en la region hasta los 25o S durante el Tardiglacial/Holoceno Temprano. La precipitacion en la region de los Andes occidentales (24o S) se incremento hasta 500 mm por ano en comparacion con los 200 mm anuales de la actualidad. Durante el periodo entre 8400 y 3000 anos AP, aproximadamente, la extrema aridez y la escasa precipitacion dominada por tormentas muy intensas pero esporadicas fueron responsables de un descenso dramatico del nivel de los lagos. A partir de los 3000 anos AP, el cinturon de lluvia tropical volvio a desplazarse hacia el sur en varias fases hasta su posicion actual (isoyeta de 200 mm anuales a 24o S). Diversos factores se consideran para explicar esta evolucion paleoclimatica: teleconexiones con el hemisferio norte, cambios en la circulacion oceanica en el Pacifico oriental, cambios ambientales en la cuenca amazonica donde se origina el vapor de agua, o diferencias en albedo (radio de entrada y salida de la radiacion solar) cubierta de nubes en la region de Atacama. Estos estudios son indispensables para atender la problematica de la adaptacion humana a los ambientes finipleistocenicos y holocenicos del Desierto de Atacama.ABSTRACTStrengthened sununer monsoon brought tropical/continental moisture as far south as 25o S during late-glacial and early Holocene times. Precipitation rates in the Altiplano of the western Andes (24o S) increased to 500 mm yr-1 compared to

High-resolution records of calibrated proxy data for the past 2000 yr are fundamental to place current changes into the context of pre-industrial natural forced and unforced variability. Although the need for regional spatially explicit comprehensive reconstructions is widely recognized, the proxy data sources are still scarce, particularly for the Southern Hemisphere and South America. We provide a 1500 yr long warm season temperature record from varved Lago Plomo, a proglacial lake of the Northern Patagonian Ice field in southern Chile (46°59' S, 72°52' W, 203 m). The thickness of the bright summer sediment layer relative to the dark winter layer (measured as total brightness; % reflectance 400–730 nm) is calibrated against warm season SONDJF temperature (1900–2009; r = 0.58, p(aut) = 0.056, RE = 0.52; CE = 0.15, RMSEP = 0.28 °C; five-year triangular filtered data). In Lago Plomo, warm summer temperatures lead to enhanced glacier melt and suspended sediment transport, which results in a thicker light summer layer and to brighter sediments (% total brightness). Although Patagonia shows pronounced regional differences in decadal temperature trends and variability, the 1500 yr temperature reconstruction from Lago Plomo compares favourably with other regional/continental temperature records but also emphasizes significant regional differences for which no data and information existed so far. The reconstruction shows pronounced sub-decadal–multi-decadal variability with cold phases in the 5th, 7th and 9th centuries, during parts of the Little Ice Age chronozone (16th and 18th centuries) and in the beginning of the 20th century. The most prominent warm phase is the 19th century which is as warm as the second half of the 20th century, emphasizing a delayed recent global warming in the Southern Hemisphere. The comparison between winter precipitation and summer temperature (inter-seasonal coupling) from Lago Plomo reveals alternating phases with parallel and contrasting decadal trends of winter precipitation and summer temperature and positive and negative running correlations(winterPP;summerTT). In the 20th century the trend of this correlation changes at 1920, 1945 and 1975 AD, and the phases with positive (negative) correlations inferred from the lake sediments are also found as a regional robust pattern in reanalysis data, and coincide with the changes of the instrumental PDO index. Enhanced circumpolar flow around 60° S is proposed for positive phases of PDO which leads to the reversed coupling and contrasting decadal trends of winter precipitation and summer temperature during PDO positive phases. Our reconstruction of the inter-seasonal coupling back to 1530 AD reproduces many features of existing PDO reconstructions from the Pacific suggesting that Lago Plomo provides a record for the regional expression of the PDO in Patagonia.

Relatively little is known about past cold-season temperature variability in high-Alpine regions because of a lack of natural cold-season temperature proxies as well as under-representation of high-altitude sites in meteorological, early-instrumental and documentary data sources. Recent studies have shown that chrysophyte stomatocysts, or simply cysts (sub-fossil algal remains of Chrysophyceae and Synurophyceae), are among the very few natural proxies that can be used to reconstruct cold-season temperatures. This study presents a quantitative, high-resolution (5-year), cold-season (Oct–May) temperature reconstruction based on sub-fossil chrysophyte stomatocysts in the annually laminated (varved) sediments of high-Alpine Lake Silvaplana, SE Switzerland (1,789 m a.s.l.), since AD 1500. We first explore the method used to translate an ecologically meaningful variable based on a biological proxy into a simple climate variable. A transfer function was applied to reconstruct the ‘date of spring mixing’ from cyst assemblages. Next, statistical regression models were tested to convert the reconstructed ‘dates of spring mixing’ into cold-season surface air temperatures with associated errors. The strengths and weaknesses of this approach are thoroughly tested. One much-debated, basic assumption for reconstructions (‘stationarity’), which states that only the environmental variable of interest has influenced cyst assemblages and the influence of confounding variables is negligible over time, is addressed in detail. Our inferences show that past cold-season air-temperature fluctuations were substantial and larger than those of other temperature reconstructions for Europe and the Alpine region. Interestingly, in this study, recent cold-season temperatures only just exceed those of previous, multi-decadal warm phases since AD 1500. These findings highlight the importance of local studies to assess natural climate variability at high altitudes.

High-resolution climate reconstructions from a range of natural archives across the world are fundamental to place current climate change into perspective. Paleoclimate records for the Southern Hemisphere are scarce and only a few quantitative high-resolution reconstructions exist for the past millennium. We present a record of annually laminated sediments of Lago Plomo (46°59′S, 72°52′W,203 m a.s.l.) located east of the Northern Patagonian Ice Field (NPI). Radiometric dating (210Pb, 137Cs, 14C AMS) is consistent with counts of millimetre-scale laminae, confirming the annual nature of the laminae couplets with a light summer and a dark winter layer. The varves were analyzed for thickness, mass accumulation rate (MAR), scanning x-ray fluorescence (XRF) and scanning reflectance spectroscopy in the visible range (VIS-RS). MAR data were calibrated against austral winter (JJA) precipitation data (CRU TS 3.0) for the period ad 1930–2002 ( r = 0.67, p(aut) < 0.05). Using a linear inverse regression model we reconstructed winter precipitation for Lago Plomo back to ad 1530. The root mean squared error of prediction (RMSEP) is small (13.3 mm/month; 12% of the average precipitation) compared with the pronounced decadal and multidecadal variability, suggesting that most of the reconstructed variability is significant. Wetter phases (reference ad 1930–2002) were observed around ad 1600, ad 1630–1690 and ad 1780–1850, and a prolonged drier period ad 1690–1780 with a multidecadal minimum centered on ad 1770. The spatial correlation for South America suggests that the JJA precipitation record from Lago Plomo is representative for large areas in the southwest between c. 41°S and 51°S.

Journal of Paleolimnology, 47 (4), ISSN:0921-2728, ISSN:1573-0417

Paleoenvironmental data from the Atacama Altiplano (21°–24°S) indicate that water, vegetation and animal resources were more abundant during lateglacial and early Holocene times than today. The rate of precipitation increased above 4000 m elevation to 400–500 mm/yr compared to the present 200 mm/yr. Dry conditions prevailed below 3500 m. Evidence of Paleoindian habitation is still missing, even though there is no evidence for environmental prohibitors during lateglacial time. The early Archaic hunters (10,820 yr B.P.-ca. 8500 yr B.P.) inhabited the Altiplano (high Puna) and its western slope, where water was available due to higher river runoff from the Altiplano, and the resources in different elevation zones were accessible. Natural resources decreased significantly during the middle Archaic period (8500-ca. 5000 yr B.P.). Lakes receded to today's levels, pedogenesis in the Altiplano terminated, and human activities were restricted to the most stable sites in the Rio Lao and the Rio Purifica catchments north of 23°S. The less stable oases south of 23°S (Salar de Atacama and Punta Negra) were abandoned. The climatic changes are best explained by shifts of the (sub)tropical circulation. © 1994 John Wiley & Sons, Inc.

Paleoenvironmental and sedimentological data from Laguna Lejia (23°30′S, 67°42′W, 4325 m) in the high Altiplano of the Chilean Atacama desert indicate that climatic conditions during late-glacial times were significantly wetter than today. A water and energy budget model was used to simulate climatic scenarios that would have resulted in the observed changes in the water levels, water surfaces, water volumes and salinity during the time interval. Different climatic scenarios for the Laguna Lejia catchment include precipitation increases of over 100% up to 400−>500 mm/yr (today 200 mm/yr) to account for the late-glacial lake levels with shorelines 15–25 m higher than at present, and a lake surface of 9–11 km2 compared to the present 2 km2. During the lake maximum about 13,500–11,300 yr B.P. finely laminated sediments consisting of Mg-calcite, diatoms and sometimes gypsum were deposited. The paleoenvironmental evidence indicates that (north)easterly wind direction prevailed, and the summer rainfall resulted from a seasonal poleward shift of the tropical circulation. The lake history of Laguna Lejia is representative for the Altiplano area between 21° and 24°S.

Los datos paleoambientales indican que los recursos de agua, vegetacion y fauna de la Puna de Atacama (>4000 m.snm), fueron abundantes durante la ultima edad glacial y Holoceno Temprano, mientras que las condiciones de aridez prevalecieron bajo los 3500 m. Los cazadores del Periodo Arcaico Temprano (ca. 10800 a 8500 AP) estaban adaptados a la alta Puna y su piedemonte, a lo largo del desague de los rios provenientes de las tierras altas, en donde los recursos de diferentes alturas se explotaban optimamente en forma trashumante dentro de distancias cortas. Los lagos se restringieron a los niveles actuales y el proceso pedogenesico concluyo en la alta Puna. Los recursos naturales decrecieron significativamente durante el Periodo Arcaico Medio (ca. 8500-5000 AP), de manera que las actividades humanas se restringieron a sitios mas estables en terminos de recursos, entre los rios Loa y Puripica al norte de los 23°. Los habitats menos estables al sur de esta latitud (salares de Atacama y Punta Negra) fueron abandonados. Las relaciones entre puntuacion de recursos, densidad ocupacional y cambios climaticos pueden ser revisados a la luz de los ajustes de los patrones de circulacion subtropical, tal como se ha advertido con nuestro conjunto de datos provenientes de la Puna de Atacama.ABSTRACTPaleoenvironmental data from the Puna de Atacama (21°- 24° S) indicate that water, vegetation and animal resources were more abundant during late glacial and Early Holocene times than today. The rate of precipitation increased above 4000 m elevation to 400->500 mm/yr compared to the present 200 mm/yr. Dry conditions prevailed below 3500 m. The early archaic hunters (ca. 10800-8500 BP) inhabited the High Puna and its western slope, where water was available due to higher river runoff from the altiplano, and the resources in different elevation zones were accesible. Natural resources decreased significantly during the Middle Archaic Period (ca. 8500-5000 BP). Lakes receded to today’s levels, the pedogenesis in the Altiplano terminated, and human activities were restricted to the most stable sites in the rio Loa and the rio Puripica catchments north of 23° S. The less stable habitats south of 23° S (Salar de Atacama and Punta Negra) were abandoned. The climatic changes are best explained by shifts of the subtropical circulation.

article i nfo Article history: The relationship between summer-autumn floods in Central Europe and climate warming is poorly con- strained by available instrumental, historical, proxy and model data. To investigate this relationship, a complete record of paleofloods, regional glacier length changes (and associated climate phases) and regional glacier advances and retreats (and associated climate transitions) are derived from the varved sediments of Lake Silva- plana(ca.1450BC-AD420;UpperEngadine,Switzerland).Incombination,theserecordsprovideinsightintothe behavior of floods (i.e. frequency) under a wide range of climate conditions. Eighty-five paleofloods are identified from turbidites in the sediments of Lake Silvaplana. Regional glacier length changes (and associated cool and/or wet and warm and/or dry climate phases) are inferred from centennial anomalies in the square root of low-pass (LP) filtered Mass Accumulation Rates (MARLP

[1] We present the first spatially and temporally highly resolved gridded reconstruction of multi-centennial precipitation variability for southern South America (SSA). A novel reconstruction approach of deriving 10,000 ensemble members based on varying predictor networks and methodological settings allows the identification of spatiotemporal changes in SSA precipitation and associated uncertainties. The summer and winter reconstructions back to AD 1498 and AD 1590, respectively, provide new evidence for multi-centennial increase in summer precipitation and an opposing decrease in winter precipitation into the 20th century. The drying in winter is significant over large parts of SSA, whereas the patterns for summer, possibly representing convective rainfall, have displayed high spatial variability. The fact that such long-term seasonal and spatial changes have occurred in the past, underlines the complex form that hydroclimatic variability might have in the future. This emphasizes the need for careful adaptation strategies as governments become attuned to the realities of climate change.

High-resolution and highly precise age models for recent lake sediments (last 100–150 years) are essential for quantitative paleoclimate research. These are particularly important for sedimentological and geochemical proxies, where transfer functions cannot be established and calibration must be based upon the relation of sedimentary records to instrumental data. High-precision dating for the calibration period is most critical as it determines directly the quality of the calibration statistics. Here, as an example, we compare radionuclide age models obtained on two high-elevation glacial lakes in the Central Chilean Andes (Laguna Negra: 33°38′S/70°08′W, 2,680 m a.s.l. and Laguna El Ocho: 34°02′S/70°19′W, 3,250 m a.s.l.). We show the different numerical models that produce accurate age-depth chronologies based on 210Pb profiles, and we explain how to obtain reduced age-error bars at the bottom part of the profiles, i.e., typically around the end of the 19th century. In order to constrain the age models, we propose a method with five steps: (i) sampling at irregularly-spaced intervals for 226Ra, 210Pb and 137Cs depending on the stratigraphy and microfacies, (ii) a systematic comparison of numerical models for the calculation of 210Pb-based age models: constant flux constant sedimentation (CFCS), constant initial concentration (CIC), constant rate of supply (CRS) and sediment isotope tomography (SIT), (iii) numerical constraining of the CRS and SIT models with the 137Cs chronomarker of AD 1964 and, (iv) step-wise cross-validation with independent diagnostic environmental stratigraphic markers of known age (e.g., volcanic ash layer, historical flood and earthquakes). In both examples, we also use airborne pollutants such as spheroidal carbonaceous particles (reflecting the history of fossil fuel emissions), excess atmospheric Cu deposition (reflecting the production history of a large local Cu mine), and turbidites related to historical earthquakes. Our results show that the SIT model constrained with the 137Cs AD 1964 peak performs best over the entire chronological profile (last 100–150 years) and yields the smallest standard deviations for the sediment ages. Such precision is critical for the calibration statistics, and ultimately, for the quality of the quantitative paleoclimate reconstruction. The systematic comparison of CRS and SIT models also helps to validate the robustness of the chronologies in different sections of the profile. Although surprisingly poorly known and under-explored in paleolimnological research, the SIT model has a great potential in paleoclimatological reconstructions based on lake sediments.

[1] We present quantitative autumn, summer and annual precipitation and summer temperature reconstructions from proglacial annually laminated Lake Silvaplana, eastern Swiss Alps back to AD 1580. We used X-ray diffraction peak intensity ratios of minerals in the sediment layers (quartz qz, plagioclase pl, amphibole am, mica mi) that are diagnostic for different source areas and hydrometeorological transport processes in the catchment. XRD data were calibrated with meteorological data (AD 1800/ 1864–1950) and revealed significant correlations: mi/pl with SON precipitation (r = 0.56, p < 0.05) and MJJAS precipitation (r = 0.66, p < 0.01); qz/mi with MJJAS temperature (r = � 0.72, p < 0.01)and qz/am with annual precipitation (r = � 0.54, p < 0.05). Geological catchment settings and hydro-meteorological processes provide deterministic explanations for the correlations. Our summer temperature reconstruction reproduces the typical features of past climate variability known from independent data sets. The precipitation reconstructions show a LIA climate moister than today. Exceptionally wet periods in our reconstruction coincide with regional glacier advances. Citation: Trachsel, M., U. Eggenberger, M. Grosjean, A. Blass, and M. Sturm (2008), Mineralogy-based quantitative precipitation and temperature reconstructions from annually laminated lake sediments (Swiss Alps) since AD 1580, Geophys. Res. Lett., 35, L13707, doi:10.1029/2008GL034121.

En este trabajo se analizo la estructura comunitaria de diatomeas depositadas en los sedimentos superficiales de ocho lagos andinos chilenos ubicados entre los 32°49' y 38°48' S. Se encontro un total de 99 taxa de diatomeas, distribuidos en 48 generos. Del total de taxa, 74 fueron identificados a nivel de especie siendo todos ellos cosmopolitas a excepcion de Eunotia andinofrequens, Gomphonema punae, Pinnularia araucanensis y Pinnularia acidicola, entre otras, que estan descritos solo para el Hemisferio Sur. Por otro lado, las muestras analizadas presentaron distinta composicion floristica de diatomeas. De esta manera, en los ensambles diatomologicos depositados en los sedimentos de las lagunas de altura Ocho, Huifa, Ensueno y Negra ubicadas sobre los 2.860 m del nivel del mar, abundaron especies bentonicas, tipicas de aguas oligotroficas y acidas como Achnanthidium exiguum, Achnanthidium minutissimum, Encyonema minutum, Pinnularia acidicola y Planothidium lanceolatum. En los ensambles diatomologicos de los lagos Galletue, Icalma y Laja, ubicados bajo los 1.360 m del nivel del mar, abundaron diatomeas planctonicas, caracteristicas de aguas alcalinas y mesotroficas como Asterionella formosa, Aulacoseira distans, Aulacoseira granulata, Cyclotella stelligera y Rhopalodia gibba

The analysis of 125 years of well-dated varved sediments in Lake Silvaplana, located at 1,791 m a.s.l. in the Upper Engadine region of south-eastern Switzerland, reveals that 7 out of the 8 climatically relevant explosive volcanic eruptions between A.D. 1880 and 2004 were followed by distinct peaks in median grain-size. Although the underlying mechanisms are yet unclear, an analysis of local meteorological data suggests that this phenomenon is unlikely to be related to any change in air temperature associated with the eruptions, but instead may be related to an increase in autumn precipitation subsequent to the eruptions that led to the erosion and fluvial transport of particles larger than normal.

This chapter reviews the history of study and the current status of Mid-Holocene climatic and cultural change in the South Central Andes, which host a wide range of different habitats from Pacific coastal areas up to extremely harsh cold and dry environments of the high mountain plateau, the altiplano or the puna. Paleoenvironmental information reveals high amplitude and rapid changes in effective moisture during the Holocene period and, consequently, dramatically changing environmental conditions. Therefore, this area is suitable to study the response of hunting and gathering societies to environmental changes, because the smallest variations in the climatic conditions have large impacts on resources and the living space of humans. This chapter analyzes environmental and paleoclimatic information from lake sediments, ice cores, pollen profiles, and geomorphic processes and relates these with the cultural and geographic settlement patterns of human occupation in the different habitats in the area of southern Peru, southwest Bolivia, northwest Argentina, and north Chile and puts in perspective of the early and late Holocene to present a representative range of environmental and cultural changes. It has been found that the largest changes took place around 9000 cal yr BP when the humid early Holocene conditions were replaced by extremely arid but highly variable climatic conditions. These resulted in a marked decrease of human occupation, “ecological refuges,” increased mobility, and an orientation toward habitats with relatively stable resources (such as the coast, the puna seca, and “ecological refuges”).

We investigate the potential of hyperspectral imaging spectrometry for the analysis of fresh sediment cores. A sediment-core-scanning system equipped with a camera working in the visual to near-infrared range (400 to 1000 nm) is described and a general methodology for processing and calibrating spectral data from sediments is proposed. We present an application from organic sediments of Lake Jaczno, a freshwater lake with biochemical varves in northern Poland. The sedimentary pigment bacteriopheophytin a (BPhe a) is diagnostic for anoxia in lakes and, therefore, an important ecological indicator. Calibration of the spectral data (BPhe a absorption ∼800 to 900 nm) to absolute BPhe a concentrations, as measured by high-performance-liquid-chromatography, reveals that sedimentary BPhe a concentrations can be estimated from spectral data with a model uncertainty of ∼10%. Based on this calibration model, we use the hyperspectral data from the sediment core to produce high-resolution intensity maps and time series of relative BPhe a concentrations (∼10 to 20 data points per year, pixel resolution 70×70 μm2). We conclude that hyperspectral imaging is a very cost- and time-efficient method for the analysis of lake sediments and provides insight into the spatiotemporal structures of biogeochemical species at a degree of detail that is not possible with wet chemical analyses.

Se sintetizan los resultados de una investigación multidisciplinaria orientada a comprender la transición entre sociedades arcaicas tardías (ca. 5000-3800 AP) y formativas tempranas (ca. 3500-2400 AP). Se propone que la ubicación de los asentamientos arcaicos y formativos en el ecorrefugio de quebrada de Tulan, se explica por un conjunto de condiciones culturales, sociales y ambientales favorables, las cuales permitieron el cambio desde una sociedad cazadora-recolectora a otra principalmente pastoralista. La evidencia arquitectónica de carácter ceremonial junto a la aparición de nuevas tecnologías, como la cerámica, litoescultura, metalurgia en oro, entre otras, y la profusión de arte rupestre, nos indican un temprano proceso de complejización en la vertiente occidental de las tierras circumpuneñas.A summary of results of multidisciplinary research aimed to the understanding of the transition between late archaic (ca. 5000-3800 BP) to early formative societies (ca. 3500-2400 BP), is presented. We suggest that the location of archaic and formative settlements in the ecorefuge of Quebrada Tulan are explained by a favorable cultural, social and environmental conditions, that allowed the transformation from a hunter gatherer society to a pastoralist one. The evidence of ceremonial architecture, the appearance of new technologies such us pottery, lito-sculpture, gold metallurgy between others and the profusion of rock art, may indicate an early complexity process in the western slope of the Circumpuna.

The Atacama Desert of the Central Andes (18°S to 28°S) has become a focal point of environmental research in recent years. Indeed, this area is a key site in several respects. It is located between the tropical and extratropical precipitation belts; the vertical gradients of ecozones range from sea level at the Pacific Coast up to high mountains that reach into the mid-troposphere at 6000 m elevation. The prominent mountain chain of the Andes stretches N-S, perpendicular to the zonal westerly airflow of the mid-latitudes, which creates distinct environmental gradients at meso-and micro-scales. Due to their sensitive location at the juncture between tropical and extratropical climate zones, paleoclimate records from this area may potentially provide important insights into the dynamics of the large-scale atmospheric circulation in the Central Andes in the past. This region therefore provides an ideal natural laboratory for paleoclimatologists.