Seasonality of modern pollen and sediment deposition in an estuarine context: the Severn Estuary Levels,southwest England

Recent sedimentological and palynological research on subfossil Holocene banded sediments from the Severn Estuary Levels suggested seasonality of deposition, registered by variations in mineral grain‐size and pollen assemblages between different parts of the bands. Here we provide data that strengthen this interpretation from sampling of modern sediments and pollen deposition on an active mudflat and saltmarsh on the margin of the Severn Estuary, and comparison with a vegetation survey and contemporary records of climate, river and tidal regimes. The results of grain‐size analysis indicate deposition of comparatively coarse‐grained silts during the relatively cool and windy conditions of winter and comparatively fine‐grained sediments during relatively warm and calm summer months. Pollen analysis demonstrates the significance of long‐term storage of pollen grains and fern spores in the estuarine waterbody, superimposed on which seasonal variations in pollen inputs from local and regional vegetation remain detectable. Copyright © 2007 John Wiley & Sons, Ltd.     

Why do people not learn from flood disasters? Evidence from Vietnam’s northwestern mountains

This article explores how the causes and impacts of a flood event as perceived by local people shape immediate responses and future mitigation efforts in mountainous northwest Vietnam. Local flood perception is contrasted with scientific perspectives to determine whether a singular flood event will trigger adjustments in mitigation strategies in an otherwise rarely flood-affected area. We present findings from interdisciplinary research drawing on both socioeconomic and biophysical data. Evidence suggests that individual farmers?? willingness to engage in flood mitigation is curbed by the common perception that flooding is caused by the interplay of a bundle of external factors, with climatic factors and water management failures being the most prominent ones. Most farmers did not link the severity of flooding to existing land use systems, thus underlining the lack of a sense of personal responsibility among farmers for flood mitigation measures. We conclude that local governments cannot depend on there being a sufficient degree of intrinsic motivation among farmers to make them implement soil conservation techniques to mitigate future flooding. Policy makers will need to design measures to raise farmers?? awareness of the complex interplay between land use and hydrology and to enhance collective action in soil conservation by providing appropriate incentives and implementing coherent long-term strategies.     

Correlation Between Compositional Parts Based on Symmetric Balances

Correlation coefficients are most popular in statistical practice for measuring pairwise variable associations. Compositional data, carrying only relative information, require a different treatment in correlation analysis. For identifying the association between two compositional parts in terms of their dominance with respect to the other parts in the composition, symmetric balances are constructed, which capture all relative information in the form of aggregated logratios of both compositional parts of interest. The resulting coordinates have the form of logratios of individual parts to a (weighted) “average representative” of the other parts, and thus, they clearly indicate how the respective parts dominate in the composition on average. The balances form orthonormal coordinates, and thus, the standard correlation measures relying on the Euclidean geometry can be used to measure the association. Simulation studies provide deeper insight into the proposed approach, and allow for comparisons with alternative measures. An application from geochemistry (Kola moss) indicates that correlations based on symmetric balances serve as a sensitive tool to reveal underlying geochemical processes.     

Subducted seamounts in an eclogite-facies ophiolite sequence: the Andean Raspas Complex, SW Ecuador

The metamorphic Raspas Complex of southwest Ecuador consists of high-pressure mafic, ultramafic, and sedimentary rocks. The Lu–Hf ages of a blueschist, a metapelite, and an eclogite overlap at around 130 Ma and date high-pressure garnet growth. Peak metamorphic conditions in the eclogites reached 1.8 GPa at 600°C, corresponding to a maximum burial depth of ~60 km. The geochemical signatures of the eclogites suggest that their protoliths were typical mid-ocean ridge basalts (MORB), whereas the blueschists exhibit seamount-like characteristics, and the eclogite-facies peridotites seem to represent depleted, MORB-source mantle. That these rocks were subjected to similar peak PT conditions contemporaneously suggests that they were subducted together as an essentially complete section within the slab. We suggest that this section became dismembered from the slab during burial at great depth—perhaps as a consequence of scraping off the seamounts. The spatially close association of MORB-type eclogite, seamount-type blueschist, serpentinized peridotite, and metasediments points to an exhumed high-pressure ophiolite sequence.     

翼龙类翼膜的折叠，褶皱以及物质特性

Preservation of wing membranes in pterosaurs is only reported from a few localities in the world, namely from the Karatau Hills, Kazakhstan (Upper Jurassic), from the Solnhofen Lithographic Limestone, Germany (Upper Jurassic), the Daohugou Beds of China (Upper Jurassic or Lower Cretaceous) and the Crato and Santana Formations, Chapada do Araraipe, NE Brazil (Lower Cretaceous).     

Saltwater intrusion in coastal regions of North America

Saltwater has intruded into many of the coastal aquifers of the United States, Mexico, and Canada, but the extent of saltwater intrusion varies widely among localities and hydrogeologic settings. In many instances, the area contaminated by saltwater is limited to small parts of an aquifer and to specific wells and has had little or no effect on overall groundwater supplies; in other instances, saltwater contamination is of regional extent and has resulted in the closure of many groundwater supply wells. The variability of hydrogeologic settings, three-dimensional distribution of saline water, and history of groundwater withdrawals and freshwater drainage has resulted in a variety of modes of saltwater intrusion into coastal aquifers. These include lateral intrusion from the ocean; upward intrusion from deeper, more saline zones of a groundwater system; and downward intrusion from coastal waters. Saltwater contamination also has occurred along open boreholes and within abandoned, improperly constructed, or corroded wells that provide pathways for vertical migration across interconnected aquifers. Communities within the coastal regions of North America are taking actions to manage and prevent saltwater intrusion to ensure a sustainable source of groundwater for the future. These actions can be grouped broadly into scientific monitoring and assessment, engineering techniques, and regulatory approaches.     

Carbon for Farmers: Assessing the Potential for Soil Carbon Sequestration in the Old Peanut Basin of Senegal

Carbon sequestration in soil organic matter of degraded Sahelian agro-ecosystems could play a significant role in the global carbon (C) uptake through terrestrial sinks while, simultaneously, contributing to sustainable agriculture and desertification control. The paper documents the results of a two-year pilot project in Senegal assessing real project opportunities with main emphasis on the West-Central Agricultural Region (Old Peanut Basin). Current total system C content in this region, calculated on the basis of in situ soil and biomass carbon measurements, amounted to 28 t ha^–1 with 11 t C ha^–1 in soils (0–20 cm) and 6.3 t C ha^–1 in trees. Potential changes in soil C, simulated with CENTURY for a 25-year period, ranged from –0.13 t C ha^–1 yr^–1 under poor management to +0.43 t C ha^–1 yr^–1 under optimum agricultural intensification. Simulated changes in crop yields varied from –62% to +200% under worst and best management scenarios respectively. Best management practices that generate the highest sequestration rates are economically not feasible for the majority of local smallholders, unless considerable financial support is provided. Especially when applied on a larger scale, such packages risk to undermine local, opportunistic management regimes and, in the long run, also the beneficiaries capacity to successfully adapt to their constantly changing environment.     

Der nacheiszeitliche Bergsturz im Kandertal (Schweiz): Alter und Auswirkungen auf die damalige Umwelt

Zusammenfassung. Beim Bau des neuen AlpTransit Lötschberg Basistunnels wurden unter murgangartig verschwemmten Ablagerungen der alten Bergsturzmasse des Kandertals Stillwasserablagerungen mit zahlreichen organischen Resten und Torflagen gefunden. Die ¹⁴C-datierten Resultate der Pollen, Makrorest-, Holz- und Holzkohleanalysen ermöglichten eine Rekonstruktion der lokalen bis regionalen Umweltgeschichte. Ein Gewässer, vermutlich ein kleiner See, begann beim Tellenfeld in Frutigen um 8800 kal. Jahre v. Chr. zu verlanden. In der näheren Umgebung wuchs von 8800 v. Chr. bis 8000 v. Chr. ein Föhrenwald (Pinus silvestris), der reichlich mit Hasel (Corylus avellana) und anderen wärmeliebenden Gehölzen (Ulmen, Linden, Eichen; Ulmus, Tilia, Quercus) und Birken (Betula) durchsetzt war. Diese für die Nordalpen sehr frühe Bedeutung der Hasel ist durch ¹⁴C-datierte Corylus-Nussfragmente (9310±50 ¹⁴C BP, 8722–8337 v. Chr.) belegt. Nach 8500 v. Chr. drängte die Hasel die Waldföhre allmählich zurück. Auf Grund der paläoökologischen Resultate muss angenommen werden, dass die Wälder um 7600 v. Chr. durch ein katastrophales Ereignis stark gestört wurden. Als Reaktion darauf kam es zu einer starken Zunahme der Waldbrände und es breiteten sich zuerst Farne und Gräser sowie wenig später Waldföhren aus. Das Gewässer wurde um 7100 v. Chr. durch verschwemmtes Bergsturzmaterial zerstört. Der geomorphologische Befund deutet darauf hin, dass diese Ereignisse in engem Zusammenhang mit dem Hauptbergsturz im Kandertal stehen, der aussergewöhnliche Ausmasse hatte (ca. 800 Millionen m³). Die Zerstörung der lokalen ökosysteme als Folge des Bergsturzes um 7600–7100 v. Chr. fiel in ein frühes holozänes Wärme- und Sonneneinstrahlungsmaximum, in dem es, wie vorgängige Untersuchungen in den Alpen und in anderen Gebirgen belegen, zu überdurchschnittlich vielen Hanginstabilitäten kam.

---

During the construction of the new AlpTransit railway line wetland sediments containing numerous fossils and peat layers were found below rockfall masses transported by debris flows. Radiocarbon-dated results of pollen, macrofossils, wood, and charcoal along with radiocarbon dating analysis were used to reconstruct the environmental history of the site. The wetland, originally probably a small lake, started to accumulate sediments at about 8800 cal. yr BC at Frutigen Tellenfeld. A pine forest (Pinus silvestris) admixed with hazel (Corylus avellana), other thermophilous arboreal taxa (Ulmus, Tilia, Quercus) and birch (Betula) grew in the surroundings of the lake. This very early importance of hazel is documented by ¹⁴C-dated Corylus nut fragments (9310±50 ¹⁴C yr BP, 8722–8337 yr BC). After 8500 BC hazel expanded on the costs of pine. The palaeo records suggest that the forests were severely disturbed by a catastrophic event at around 7600 BC. In response, forest fires strongly increased and ferns and grasses expanded and then pine stands established. At ca. 7100 BC the lake was abruptly destroyed by rockfall masses transported by a debris flow. The geomorphic situation suggests that these events were closely related with the main Kander valley rockfall, which had an exceptional size (800 millions m³). Local environmental catastrophes as a consequence of the rockfall at 7600–7100 BC occurred during an early Holocene thermal and solar irradiation maximum. As documented by previous investigations, this period was characterised by pronounced slope instabilities in the Alps and elsewhere.

Manuskript eingegangen 9. Februar 2004 Revidierte Fassung angenommen 17. Januar 2005