Phase relationship between sea level and abrupt climate change

Direct traces of past sea levels are based on the elevation of old coral reefs at times of sea level highstands. However, these measurements are discontinuous and cannot be easily correlated with climate records from ice cores. In this study we show a new approach to recognizing the imprint of sea level changes in continuous sediment records taken from the continental slope at locations that were continuously submerged, even during periods of sea level lowstand. By using a sediment core precisely synchronized with Greenland ice cores, we were able to recognize major floods of the Mediterranean continental shelf over the past 270 kyr. During the last glacial period five flooding events were observed at the onset of the warmest Greenland interstadials. Consistent correspondence between warm climate episodes and eustatic sea level rises shows that these global flooding events were generated by pronounced melting of the Northern Hemisphere ice sheets, due to rapid intensification of Atlantic Meridional Overturning Circulation.The method described in this study opens a new perspective for inter-hemispheric synchronization of marine climate records if applied in other continental margins from the Southern Hemisphere or the equatorial regions.     

Contrasting sediment flux in Val Lumnezia (Graubünden, Eastern Swiss Alps), and implications for landscape development

This paper presents qualitative estimates of sediment discharge from opposite valley flanks in the S–N-oriented Val Lumnezia, eastern Swiss Alps, and relates inferred differences in sediment flux to the litho-tectonic architecture of bedrock. The valley flank on the western side hosts the deep-seated Lumnezia landslide where an area of ca. 30 km² has experienced slip rates of several centimetres per year, potentially resulting in high sediment discharge to the trunk stream (i.e. the Glogn River). High slip rates have resulted in topographic changes that are detectable on aerial photographs and measurable with geodetic tools. In contrast, a network of tributary channels dissects the valley flank on the eastern side. There, an area of approximately 18 km² corresponding to < 30% of the surface has experienced a change in the landscape mainly by rock avalanche and rock fall, and the magnitudes of changes are below the calibration limit of digital photogrammetry. We thus infer lower magnitudes of sediment discharge on the eastern tributaries than on the western valley side, where landsliding has been the predominant erosional process. These differences are interpreted to be controlled by the dip-slope situation of bedrock on the western side that favours down-slope slip of material. Morphometric investigations reveal that the western valley side is characterized by a low topographic roughness because this valley flank has not been dissected by a channel network. It appears that high sediment discharge of the Lumnezia landslide has inhibited the establishment of a stable channel network and has largely controlled the overall evolution of the landscape. This contrasts to the general notion that channelized processes exert the first-order control on landscape evolution and formation of relief and needs to be considered in future studies about landscape architecture, drainage network and sediment discharge.     

Evolution of contourite systems in the late Cretaceous Chalk Sea along the Tornquist Zone

Based on integration of seismic reflection and well data analysis this study examines two major contourite systems that developed during the late Cretaceous in the southern Baltic Sea. The evolution of these Chalk Sea contourite systems between the Kattegat and the southern Baltic Sea started when Turonian to Campanian inversion tectonics overprinted the rather flat sea floor of the epeiric Chalk Sea. The Tornquist Zone and adjacent smaller blocks were uplifted and formed elongated obstacles that influenced the bottom currents. As a consequence of the inversion, the sea floor west of the Tornquist Zone tilted towards the north‐east, creating an asymmetrical sub‐basin with a steep marginal slope in the north‐east and a gentle dipping slope in the south‐west. A south‐east directed contour current emerged in the Coniacian or Santonian along the south‐western basin margin, creating contourite channels and drifts. The previously studied contourite system offshore Stevns Klint is part of this system. A second, deeper and north‐west directed counter‐flow emerged along and parallel to the Tornquist Zone in the later Campanian, but was strongest in the Maastrichtian. This bottom current moderated the evolution of a drift‐moat system adjacent to the elevated Tornquist Zone. The near surface Alnarp Valley in Scania represents the Danian palaeo‐moat that linked the Pomeranian Bay with the Kattegat. The previously studied contourite system in the Kattegat represents the north‐western prolongation of this system. This study links previous observations from the Kattegat and offshore Stevns Klint to the here inferred two currents, a more shallow, south‐east directed and a deeper, north‐west directed flow.     

Ecological criteria, participant preferences and location models: A GIS approach toward ATV trail planning

This paper presents a geographic information system (GIS)-based method for recreational trail location for all-terrain vehicles (ATVs) which considers environmental factors, as well as rider preferences for trail attributes. The method utilizes the Least-Cost Path algorithm within a GIS framework to optimize trail location. The trail location algorithm considered trail impacts and benefits associated with water bodies, slope, land ownership, noise, trail separation, views, and rider preferences for vegetation types and loop trails. Alternative trails were generated to highlight the influence of different preferences for trail attributes and to demonstrate the capabilities of the Least-Cost Path algorithm as applied to trail location. The method shows promise for use in generating ATV trails, as well as other types of recreational trails, for consideration in recreational planning and analysis.     

Source identification and global implications of black carbon

Black carbon(BC)is one of the short-lived air pollutants that contributes significantly to aerosol radiative forcing and global climate change.It is emitted by the incomplete combustion of fossil fuels,biofuels,and biomass.Urban environments are quite complex and thus,the use of mobile jointly with fixed monitoring provides a better understanding of the dynamics of BC distribution in such areas.The present study addresses the measurement of BC concentration using real-time mobile and ambient monitoring in Barranquilla,an industrialized urban area of the Colombian Caribbean.A microaethalometer(MA200)and an aethalometer(AE33)were used for measuring the BC concentration.The absorption ?ngstr?m exponent(AAE)values were determined for the study area,for identifying the BC emission sources.The results of the ambient sampling show that vehicle traffic emissions prevail;however,the influence of biomass burning was also observed.The mean ambient BC concentration was found to be 1.04±1.03μg/m³ and varied between 0.5 and 4.0μg/m³.From the mobile measurements obtained in real traffic conditions on the road,a much higher average value of 16.1±16.5μg/m³ was measured.Many parts of the city showed BC concentrations higher than 20μg/m³.The spatial distribution of BC concentration shows that vehicle emissions and traffic jams,a consequence of road and transport infrastructure,are the factors that most affect the BC concentration.A comparison of results obtained from two aethalometers indicates that the concentrations measured by MA200 are 9%lower than those measured by AE33.The AAE obtained was found to vary between 1.1 and 1.6,indicating vehicular emissions as the most crucial source.In addition,it was observed that the BC concentration on working days was 2.5 times higher than on the weekends in the case of mobile monitoring and 1.5 times higher in the case of ambient monitoring.     

The non-Gaussian tail of cosmic-shear statistics

Owing to gravitational instability, an initially Gaussian density field develops non-Gaussian features as the Universe evolves. The most prominent non-Gaussian features are massive haloes, visible as clusters of galaxies. The distortion of high-redshift galaxy images because of the tidal gravitational field of the large-scale matter distribution, called cosmic shear, can be used to investigate the statistical properties of the large‐scale structure (LSS) . In particular, non-Gaussian properties of the LSS will lead to a non-Gaussian distribution of cosmic-shear statistic. The aperture mass ( M _ap) statistics, recently introduced as a measure for cosmic shear, is particularly well suited for measuring these non-Gaussian properties. In this paper we calculate the highly non-Gaussian tail of the aperture mass probability distribution, assuming Press–Schechter theory for the halo abundance and the 'universal' density profile of haloes as obtained from numerical simulations. We find that for values of M _ap much larger than its dispersion, this probability distribution is closely approximated by an exponential, rather than a Gaussian. We determine the amplitude and shape of this exponential for various cosmological models and aperture sizes, and show that wide-field imaging surveys can be used to distinguish between some of the currently most popular cosmogonies. Our study here is complementary to earlier cosmic-shear investigations, which focused more on two- and three-point statistical properties.     

Macrophyte-based bioindication in rivers - A comparative evaluation of the reference index (RI) and the trophic index of macrophytes (TIM)

Submerged macrophyte vegetation has been mapped in four calcareous groundwater-fed streams in Bavaria (southern Germany) in order to compare and assess two different methods of river bioindication. The first one, the trophic index of macrophytes (TIM), is a tool to assess the trophic status of running waters. In contrast, the reference index (RI) is an ecological index which evaluates the difference between a reference community and the actual submerged vegetation, depending on the river type, as required by the Water Framework Directive. Water nutrient concentrations were measured once at selected sites in all water courses.The TIM reflects water phosphorus concentrations, accounting also for nutrients enrichment in the sediment, and is not influenced by shading, depth, substrate and flow velocity of the water course. The TIM is very sensitive to small variations in P concentration when the P level is low, while the index tends to a maximum as soluble reactive phosphorus (SRP) and total phosphorus (Ptot) exceed a certain value.The RI indicates river ecological status which is not only influenced by trophic status but by every factor leading to a deviation of the actual macrophyte community from the reference community. In the investigated rivers the RI indicated reduced flow velocity caused by milldams and shading by riparian vegetation, in addition to trophic status.In rivers that are at the boundary between two different river types, classification of river type can play a crucial role for river status assessment. Incorrect classification of river type can lead to both, a “too good” and “too bad” assessment.     

Tectonic Evolution of an Early Precambrian High-Pressure Granulite Belt in the North China Craton

A large-scale high-pressure granulite belt (HPGB), more than 700 km long, is recognized within the metamorphic basement of the North China craton. In the regional tectonic framework, the Hengshan-Chengde HPGB is located in the central collision belt between the western block and eastern block, and represents the deep crustal structural level. The typical high-pressure granulite (HPG) outcrops are distributed in the Hengshan and Chengde areas. HPGs commonly occur as mafic xenoliths within ductile shear zones, and underwent multipile deformations. To the south, the Hengshan-Chengde HPGB is juxtaposed with the Wutai greenstone belt by several strike-slip shear zones. Preliminary isotopic age dating indicates that HPGs from North China were mainly generated at the end of the Neoarchaean, assocaited with tectonic assembly of the western and eastern blocks.     

Boron in the Bolivian tin belt

Tourmaline alteration and high boron contents are typical features of the magmatic-hydrothermal systems of the Bolivian tin province. The average boron content in melt inclusions of quartz phenocrysts from tin porphyry systems is 225 ppm (1σ-variation range: 110–420 ppm; n=12) and suggests a magmatic boron input to the hydrothermal tin systems, and not shallow post-magmatic leaching of boron from pelitic country rocks. Boron data from melt inclusions correlate positively with cesium, rubidium and arsenic, and negatively with lithium, titanium and zirconium, and define magmatic fractionation trends. The generally high B, As, Cs and Li contents in melt inclusions suggest involvement of pelitic source lithologies undepleted in these fluid-mobile components, i.e. first-cycle metamorphic rocks. Magmatic fractionation modified the trace-element contents within a one-log-unit range. Bulk-rock Nd isotope data (ɛ_Nd−5 to −10) are in agreement with the dominantly intracrustal geochemical signature of the Bolivian tin porphyry systems, but also imply a variable but minor mantle input. The metallogeny of the tin belt is likely a consequence of intracrustal melting of Lower Paleozoic pelitic and slightly carbonaceous source material, combined with an extended magmatic evolution. The long-lived thermal preparation of the root zones of the silicic systems is provided by mafic magma which also leaves a chemical imprint in the form of the hybrid dacitic bulk composition of the tin porphyry systems. Received: 6 August 1998 / Accepted: 19 August 1999