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Abstracts / Quaternary International 279-280 (2012) 462–565
high levels of endemicity. Global analysis of Mediterranean fire activity suggests a rapid rise in fires between14,000 and 13,000 cal yr BP, followed by a decline from 13,000 to 12,000 cal yr BP. After 9000 cal yr BP, fire activity increased in all Mediterranean regions until the middle Holocene. Analysis of five isolated Mediterranean regions reveals a coherent pattern in fire activity across all locations beginning by 9500 cal yr BP. As Mediterranean-type vegetation developed between 5000-2000 cal BP, intensified climate variability associated with ocean upwelling, produced increased variability in fire regimes and a potential mechanism for the development of Mediterranean diversity. Identifying the long-term interrelationship between fire and the presence and abundance of endemic species will provide a better understanding of the role fire plays in the development and long-term stability of Mediterranean hotspots. With increasing anthropogenic pressure, and high levels of fire suppression in Mediterranean hotspots, more research is necessary to aid future conservation and fire management strategies in these unique regions. MULTIPLE CONTROLS ON DRAINAGE BASIN MORPHOMETRIES IN THE WESTERN ESCARPMENT OF THE PERUVIAN ANDES Mareike Trauerstein. Institute of Geological Sciences, University of Be, Switzerland E-mail address:
[email protected]
We analyze tectonic, lithologic, and climatic controls on landscape geometries of the Western Escarpment of the Peruvian Andes, where the Nazca Plate is actively subducted beneath the South American Plate. The landscape in this part of the Andes is characterized by prominent knickzones that record the erosional response to a Late Miocene phase of rock uplift. The analysis of >80 drainage basins shows a positive correlation between the subduction angle and mean hillslope gradients, where a flat subduction leads to a higher total topographic relief and, normalized to a topographic length scale, to steeper hillslopes. We thus suggest that the tectonic situation exerts a first order control on channel and hillslope geometries. The bedrock geology in the investigated drainage basins comprises Tertiary volcanic rocks, Mesozoic plutonic and metamorphic units and predominantly Quaternary sediments. Channels exhibit channel steepness (ks) values that depend on these lithologies, but the pattern is rather related to the location relative to the knickzone than to the mechanical properties of bedrock. In particular, the lowest ks values are found on the Meseta upstream the knickzones where the volcanic units form the cap rock, whereas the highest values are measured for the plutonic rocks downstream the knickzones. Finally, we investigated the relationships between the landscape metrics and climate proxies. The precipitation pattern in the investigated area is characterized by negative gradients in both east-west and north-south directions. A weak correlation between mean annual precipitation and mean hillslope angle is observed. The influence of climate on the channel and hillslope morphometries appears more obvious if segments upstream and downstream the knickzones are analyzed separately. An even stronger correlation is discovered if precipitation patterns related to El Niño events are considered. GROUNDWATER RESOURCES ASSESSMENT UNDER THE PRESSURES OF HUMANITY AND CLIMATE CHANGE (GRAPHIC) - UNESCO'S GLOBAL NETWORK OF GROUNDWATER AND CLIMATE SCIENTISTS
global project on Groundwater and Climate Change (GRAPHIC). The project is aimed at promoting and advancing sustainable groundwater management considering projected climate change and linked human effects by facilitating communication and exchange of information and conducting case studies globally. Based on scientific findings GRAPHIC derives management recommendations to inform policy and decision makers at different levels. Among the methods applied in the framework of GRAPHIC in order to improve our understanding of how groundwater interacts within the global water cycle, and responds to complex pressures of human activities and climate change, paleoindicators of climate change play an important role. The study of chemical and isotopic proxies in groundwater or sediments help understanding the impacts of past climate changes on the subsurface environment. Knowing the response of hydrological systems to past climate changes may provide indications to forecast their behavior in the future (e.g. seawater intrusion in coastal aquifers due to past sea level rise; groundwater recharge rates under past precipitation patterns; effects of extreme weather on groundwater systems). WINTER ARCTIC OSCILLATION SIGNAL IN A EUROPEAN TREE-RING d18O NETWORK Kerstin Treydte. Swiss Federal Research Institute WSL, Switzerland E-mail address:
[email protected]
We present a large and well-replicated tree-ring d18O network, developed in the EU-projects MILLENNIUM and ISONET, with 33 European sites ranging from Fennoscandia to the Mediterranean region. Based on PCA we could define three European sub-regions: Scandinavia, central Europe and the western Mediterranean. Spatial correlations with air pressure fields indicate that in Scandinavia and the Mediterranean, regional mid-tropospheric air pressure systems during summer are mirrored in tree-ring d18O. In contrast, central European tree-ring d18O strongly record dipole-like large-scale atmospheric circulation patterns during winter. The winter signal is supported by highly significant correlations of PC1 to JanuaryMarch data of a central European precipitation d18O record and relatively weak correlations to summer months. Moreover, PC1 strongly corresponds to winter AO-indices with a robust signal throughout the whole study period (1900-2003). This large-scale atmospheric winter signal is assumed to originate from source water uptaken from deeper soil water pools preserving winter precipitation/snow-melt water far into the growing season, particularly accessible by the deep root system of Quercus species. In Scandinavia, more regional-scale low-pressure systems in summer are expected to provide the main water source for the trees there. This may partly also hold for shallow and dry soils in the Mediterranean, also not allowing for longer-term water storage. In addition to the source water control, summer signals are probably related to physiological processes at the canopy resulting in leaf water enrichment during transpiration and postphotosynthetic fractionation effects. Additional analyses are going (1) to test the robustness of the PCs and the AO-signal over the past 400 years and (2) to disentangle the climatic and physiological drivers of tree-ring d18O on local to regional scale by applying leaf water/wood cellulose models. SEDIMENTOLOGICAL CHARACTERISTICS OF THE SLOPE DEPOSITS OF SERRA DA ESTRELA (PORTUGAL): FIRST RESULTS Alexandre Trindade. University of Lisbon, Portugal E-mail address:
[email protected]
Holger Treidel. UNESCO, France E-mail address:
[email protected]
Groundwater is a globally important resource supplying a major part of the global population with drinking water, and sustaining agriculture, industries, lakes, wetlands, and groundwater dependant ecosystems. Human activities, including contamination and abstraction of groundwater resources and the uncertain consequences of climate change are threatening the resource. Our knowledge on how climate change may affect the current availability and future sustainability of global groundwater resources remains, however, limited to date. Moreover, little attention has been paid to the role that groundwater is expected to play in societal adaptation to climate change, especially in arid zones and during periods of extended drought. To address these concerns, UNESCO-IHP launched its
Serra da Estrela is the highest mountain in Portugal (1993 m ASL) and part of the Iberian Central Cordillera. The mountain has a strong relief and a lithological diversity with several types of granitoids and metasediments. Most of the western plateau area was glaciated during the Last Glacial Maximum and it's morphology is dominated by glacial landforms. Serra da Estrela is a landmark in studies of glacial and periglacial geomorphology in Portugal. Vieira (2004) produced a detailed geomorphological map of the mountain, identifying several slope deposit types and outcrops of stratified slope, head and different types of debris-flow deposits. Based on the geomorphological analysis of the relationships between glacial and periglacial evidence, a first relative chronology was presented. However, a detailed and systematical sedimentological analysis has not been conducted before and absolute ages are also lacking.
Abstracts / Quaternary International 279-280 (2012) 462–565
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Our work is based on the systematical application of sedimentological techniques of analysis and dating, supported by detailed geomorphological surveying and by spatial analysis using GIS. The sedimentological analysis includes macroscopic description of sedimentary units and structures, fabric analysis, clast morphometry and characteristics of matrix elements. Samples from different stratigraphic units of slope deposits are being analyzed for grain-size analysis of coarse and fine fractions, organic matter content, thin-section micromorphology and exoscopy of quartz grains. This poster will present the first results of the lithostratigraphy and fabric analysis of key slope deposit, and a general methodological framework of the approach we are applying. Our main goals are to contribute to the better understanding of the morphogenetical significance of the different types of slope deposits including clarifying the role of cold environment processes and also to develop a chronological framework for the Late Quaternary evolution of the slope environment.
estimates available. The maps are produced for 10 PFTs (for LPJ-GUESS) and 3 major land-cover types (for RCA3) at a spatial resolution of 1ox1o for five time-windows with contrasting land-cover. REVEALS estimates are now available for most of the countries in the study area and are compared with past land-cover obtained through different approaches such as historical data in conjunction with population/land-use models (e.g.Kaplan et al.2009). A combination of estimates using complementary methods might be a sound way forward in the attempt to produce past land-cover data useful for climate modelling.
LATE QUATERNARY AEOLIAN RECORD AND PALEOCLIMATIC CONDITIONS AT THE DISTAL ANDEAN PIEDMONT, SOUTHERN MENDOZA, ARGENTINA
As ice sheets expand and contract they leave sedimentary records that can be interpreted to help define former ice sheet extent. For example, ice rafted debris in ocean sediment cores have been cited as evidence of deglaciation events: periods when icebergs transport large-grained sediments away from the continental margin. Here we describe recent changes in calving style at Jakobshavn Isbrae and interpret the consequences for sediment deposition in the fjord and off the coast of Greenland. Jakobshavn Isbrae is one of the largest outlet glaciers in Greenland. After remaining in a relatively stable position for several decades, the 12-km long floating tongue thinned substantially after 1997 and completely disintegrated by 2002. The glacier has now retreated w15 km, terminus speeds have doubled, and calving occurs primarily from a grounded terminus. The change in calving style, from large tabular icebergs to smaller rotated icebergs from a grounded terminus, has significant implications for sediment transport. The floating tongue was subject to basal melt rates exceeding 100 m/a. Thus, all basal debris would have melted out near the terminus. In contrast, grounded calving often proceeds by the rotation of large icebergs, which brings basal debris to the surface. These icebergs are then advected down fjord and, if they can clear all obstructions, eventually into the open ocean. Larger icebergs will get trapped at the sill at the fjord entrance and have a higher chance of depositing any trapped sediment there. Rates of icerafted debris deposition in the open ocean vary greatly dependent on calving style and are indicative of calving from a grounded position, such as is currently observed, while coarse grained sediments in the inner fjord should be indicative of a floating tongue.
Alfonsina Tripaldi. University of Buenos Aires, Argentina E-mail address:
[email protected]
The eastern plain of Mendoza province, in the distal Andean piedmont of Argentina (32o –36o S, South America) presents extensive aeolian sandy surfaces, in many cases with dunefields. The aeolian cover is partial stabilized by a shrub steppe of Larrea spp and Gramineae, with aeolian processes occurring barely at the crests and steep sides. This is a semiarid region with mean annual precipitation and temperature of 350 mm and 5oC, respectively, dominated by summer rainfall of a monsoon-like system, influenced by the South Atlantic anticyclone. Aeolian sand grades laterally to fluvial deposits (Mendoza, Tunuyán, Diamante, Atuel and Desaguadero-Salado rivers), wetlands (e.g. Guanacache lakes) and saline mud flats. Late Quaternary records of these aeolian deposits were studied in river bank exposures from arroyos of southern Mendoza, together with some preliminary information from dune augering in the near Médanos de los Naranjos dunefield. In the river bank sections, channel, floodplain, fluvio-aeolian interaction, reworked pyroclastic and aeolian deposits were identified, described and sampled for OSL dating. Facies analysis indicates ephemeral fluvial aggradation between 40-60 ka and 31-21 ka, under generally semiarid conditions. During LGM (21-14 ka) there were significant aeolian activity represented by dune migration and aeolian sand sheet accretion. Médanos de los Naranjos dunefield, partially eroded in some zones, is formed by crescentic dunes and megadunes, with variable orientations. There are mainly NE-SW crests and leeward facing W-NW at the western area, while at the E crests show a NW-SE orientation and leewards to the NE. Augered sand from different hollows evidences aeolian sedimentation at ca. 10 ka (6 m depth sample), between ca. 4-6 ka (2 m depth samples) and at ca. 2.3 ka (1 m depth sample). These inferred paleoenvironmental conditions of southern Mendoza plain are in broad agreement with regional evidence. MODEL ESTIMATES OF HOLOCENE REGIONAL LAND-COVER INFERRED FROM POLLEN RECORDS FOR CLIMATE MODELLING Anna-Kari Trondman. Linnaeus University, Sweden E-mail address:
[email protected]
In order to refine climate models and to get a better understanding of the climate-vegetation feedbacks, the LANDCLIM project (sponsored by VR and NordForsk) has the objective to produce quantitative estimates of regional land-cover changes during the Holocene in NW Europe. The purpose is to evaluate the effects that human-induced land-cover changes may have had on the regional climate through altered feedbacks. We use fossil pollen data and the REVEALS model (Sugita 2007) to produce estimates of the percentage cover of individual taxa and plant functional types (PFTs). The past plant cover will be compared with the outputs of the dynamic vegetation model LPJ-GUESS (Smith et al. 2001), and applied to run the regional climate model RCA3 (Samuelsson et al. 2010). The first land-cover estimates are based on REVEALS runs using pollen from both lakes and bogs with chronologies based on 3 dates, 25 taxa (entomophilous taxa excluded) and, for each taxon, the mean of all pollen productivity
RETREATING JAKOBSHAVN ISBRAE ACTS AS A HEINRICH-EVENT-LIKE SOURCE OF ICE-RAFTED DEBRIS Martin Truffer. University of Alaska, United States E-mail address:
[email protected]
IMPLICATIONS FROM FLUVIAL TERRACES FOR GEOMORPHIC EVOLUTION OF THE PULI BASIN, TAIWAN Chia-Han Tseng. Freie Universität Berlin, Germany E-mail address:
[email protected]
Taiwan Island is located on the active convergent boundary where the continuous orogeny has led to the formation of mountains in central and eastern part of Taiwan. Several basins possibly resulting from tectonic activities are observed in the Hsuehshan Range in the central Taiwan. The morphodynamics has been changing the landscape of these basins but the ages of sediments and the time when these basins formed are still unknown. Therefore, in this study we want to reconstruct the evolution of the topography around and within these basins on an upper Pleistocene to Holocene time scale. On the southwestern edge of the Puli Basin which is the biggest of the basins in central Taiwan, a series of fluvial terraces developed due to the incision of the Taomi River, flowing directly into the Puli Basin. The upper part of the fluvial terraces, with an elevation of about 110 m estimated from the riverbed of the Taomi River, is lateritic formation and the middle part is composed of alluvial materials. In the first phase, a cross-section profile at the lower part of the fluvial terraces was sampled for sedimentological, pedological and geochronometrical analysis by means of Optically Stimulated Luminescence (OSL) and radiocarbon dating. The results of the OSL and radiocarbon dating and the materials composition of the fluvial terraces will be important references to the paleoenvironment. Furthermore, combining the results with high resolution Digital Terrain Model (DTM), we can define landscape features and reconstruct the geomorphic evolution of the Puli Basin in Quaternary.
