Logical data modelling for geographical applications

Abstract.

A formal, yet practical, GeoRelational Data Model (GRDM) is presented for the logical database design phase of the development of spatial information systems. Geographic applications are viewed in the context of information systems development. The generic needs of modelling spatial data are analyzed; it is concluded that they are not served satisfactorily by existing data models, so specifications of modelling tools for spatial application design are given. GRDM provides a set of representational constructs (relations and layers for the logical schema; virtual layers, object classes and spatial constraints for the user views) on top of well-established models. It constitutes part of a full, easily automated application design methodology. Extensive examples demonstrate the relevance, and ease-of-use of the platform-independent GRDM.     

Isotopic composition and origin of polar precipitation in present and glacial climate simulations

The Hamburg atmospheric general circulation model (AGCM) ECHAM‐4 is used to identify the main source regions of precipitation falling on Greenland and Antarctica. Both water isotopes H₂¹⁸O and HDO are explicitly built into the water cycle of the AGCM, and in addition the capability to trace water from different source regions was added to the model. Present and LGM climate simulations show that water from the most important source regions has an isotopic signature similar to the mean isotope values of the total precipitation amount. But water from other source regions (with very different isotopic signatures) contributes an additional, non‐negligible part of the total precipitation amount on both Greenland and Antarctica. Analyses of the temperature‐isotope‐relations for both polar regions reveal a solely bias of the glacial isotope signal on Greenland, which is caused by a strong change in the seasonal deposition of precipitation originating from nearby polar seas and the northern Atlantic. Although the performed simulations under LGM boundary conditions show a decrease of the δ ¹⁸O values in precipitation in agreement with ice core measurements, the AGCM fails to reproduce the observed simultaneous decrease of the deuterium excess signal.     

The Ballachulish Igneous Complex, Scotland: Petrography, Mineral Chemistry, and Order of Crystallization in the Monzodiorite-Quartz Diorite Suite and in the Granite

The igneous complex of Ballachulish is a composite calc-alkalinepluton of Caledonian age (412 ? 28 Ma), emplaced in Dalradianmetasediments at a pressure of 3 ? 0–5 kb (c. 10 km depth).The 4 by 7 km intrusion is composed of a zoned monzodiorite-quartzdiorite envelope with a distinct flowand deformation-foliation,surrounding a younger core of porphyritic granite. Two-pyroxene thermometry, Fe-Ti oxide thermobarometry, and stabilityrelationships of ternary feldspars, biotite, and amphibolesare used to calibrate the 3 kb isobaric crystallization sequencewith respect to the following parameters: the fractionationstage of the host rocks, the water content of the magmas, phasecompositions, and oxygen fugacity. Plagioclase, augite, andoxides generally yielded submagmatic temperatures due to theextensive recrystallization and re-equilibration of these phasesin the 900–l550?C subsolidus range. The ‘dry’monzodiorites apparently contained less than 1 wt. % initialmagmatic water, and remained H₂O-deficient and vapor-absentthroughout their entire crystallization range. In contrast,2.5–3 wt.% initial H₂O is estimated for the more fractionatedquartz diorites and the younger granites. The main crystallizationinterval for Opx–Cpx–Plg primocrysts in the dioritescovers c. 1100–950?C. Late-magmatic biotite and alkalifeldspar join the paragenetic sequence below 980?860?C, at fO₂near NNO. A solidus temperature of c. 900?C is inferred forthis ‘dry’ system, in which amphiboles are entirelysubsolidus. At the present level of emplacement, crystallizationintervals of {small tilde} 1050–690?C and{small tilde}900–680?C are suggested for the quartz diorites and thegranites, which probably terminated crystallization in the presenceof a hydrous fluid.     

Evolution of a small intraplate basaltic lava field: Jerrabattgulla Creek,upper Shoalhaven River catchment,southeast New South Wales

The Jerrabattgulla Creek basalts are in the upper catchment of the Shoalhaven River of southeastern New South Wales. The basalts erupted into a narrow, north-draining valley and modified the local drainage system, re-routing the paleo-Jerrabattgulla Creek, preserving a series of sub-basaltic quartzose gravels with silcretes in the paleovalley. The paleovalley indicates that a north-flowing drainage existed in this place in the Miocene. The high-relief, narrow valley has preserved a volcanic stratigraphy allowing the magmatic evolution of this small lava field to be determined. The lavas have a large compositional range from olivine nephelinite through to quartz tholeiite, which is unusual in such a small lava field. They represent three distinct magma batches, most likely from an amphibole–apatite metasomatised sub-continental lithospheric mantle, and underwent fractional crystallisation of olivine, clinopyroxene and plagioclase and assimilated upper crust. The lava field underwent temporal change from dominantly alkaline, to mixed alkaline and subalkaline, to dominantly alkaline magmatism over the course of its evolution.     

Holocene climatic variations and postglacial sea-level rise geochemically recorded in the sediments of the brackish karst lake An Loch Mor, western Ireland

Palaeohydrology of the brackish karst lake An Loch Mór (Inis Oirr) was reconstructed based on its 11 600 year sedimentation record. Low calcareous early Holocene sediments, characterized by high TOC contents and deposited at generally low accumulation rates, show a gradual decrease upwards in the concentration of the siliciclastic sediment until c . 7000 cal. yr BP. From c . 9000 cal. yr BP, sediment accumulation became increasingly dominated by the deposition of autochthonous calcite and organic matter. The deposition of autochthonous calcite and its chemical composition (Ca/Sr, Ca/Mg) are determined by the subsurface inflow of freshwater from the catchment of the lake and by the balance between freshwater and seawater influx. During the early Holocene, the lake mainly received input of sea salt by sea-spray. The sediments document the further development from seasonal towards the onset of diurnal infiltration of seawater at c . 5100 cal. yr BP. At that time, the relative sea level must have risen nearly to its present level in Galway Bay. Diurnal seawater infiltration during high tides was controlled by freshwater input. Freshwater inflow from the catchment gradually increased with human impact on local vegetation (EVPT decrease). Permanent diurnal seawater infiltration in concert with this general freshwater increase made the geochemical sedimentation record highly sensitive to changes in annual precipitation. We use information from the palynological record to interpret geochemically inferred freshwater inflow variations in terms of dry and wet climatic periods and document distinct century-scale successions between wet and dry climatic episodes for western Ireland.     

Pesticide behaviour in Quaternary sediments

Pesticides are very often spread in agricultural and forest areas covering important groundwater bodies in Quaternary sand and gravel deposits. They are mostly synthetic organic chemicals used for plant protection against predators and competing herbs. According to their radius of action they can be separated into herbicides, insecticides, nematicides, acaricides, molluscicides, rodenticides, fungicides, and bactericides. With respect to the risks of groundwater contamination by pesticides, only the first three groups are of interest. For a risks assessment of groundwater contamination, detailed knowledge of the geochemical behaviour of the pesticides and of the physico-chemical processes controlling their persistence and transport in the sediments is necessary. These processes can be summarized as dissolution/precipitation, adsorption/ desorption, degradation and transport processes in the soil in the unsaturated and saturated zones. Furthermore, the type of plant production being established in the area has to be considered. In the case of crop rotation the applied pesticides are changed every year and the risk of groundwater contamination is normally low because of retardation and degradation. In soils used for special-purpose crops, an accumulation of pesticide residues is possible, because the same substances are applied every year. Especially on sandy soils the leaching of residues can lead to severe groundwater contamination.     

EFFECTS OF MAN'S ACTIVITIES ON GROUNDWATER QUALITY / Les effets des activités de l'homme sur la qualité des eaux souterraines

Abstract

The changes in groundwater quality that result from man's activities are reviewed. This paper considers the various geochemical reactions, the biochemical processes and the physical processes that take place as well as the sources of pollution. Suggestions are made for future research and practical guidance given for avoidance of pollution of groundwater or minimizing its effects.     

Post-eruptive development of the Ukinrek East Maar since its eruption in 1977 A.D. in the periglacial area of south-west Alaska

Maar eruptions form small initially steep‐walled basins that contain important archives for the climatic and palaeoenvironmental history in continental areas. The two Ukinrek Maars in south‐western Alaska erupted between 30 March and 9 April 1977 and are the best‐documented maars that have erupted in historical time. This study presents a preliminary analysis of geomorphology, hydrology, magnetic susceptibility, geochemistry and sedimentology data of a field study in August 2004. These results, photographs and topographic surveys are combined for reconstructing the post‐eruptive evolution of Ukinrek East Maar. Within less than 30 years the initially polygonal shape of the crater with nearly vertical crater walls has developed into an almost elliptic form with slopes of 35° inclination on debris fans between a few escarpments. The water table and the crater floor have risen significantly and the crater diameter:depth ratio increased from 3·4 to 5·7, whereas the average height of the crater rim remained almost constant. The main sub‐aerial resedimentation process is formation of rock falls, rock slumps and scree resulting in debris flows and turbidites within the lake that is ice‐covered throughout about half of the year. Distal lake sediments consist of laminated minerogenic clayey‐sandy silts that document frequent turbidity currents. From the linear sedimentation rate of only ca 5 mm year^?1 in 17 cm long cores it may be concluded that the largest portion of the crater sediments formed within the first few months of the maar history, however, this has to be confirmed by future studies.