Petrogenesis of the Post-kinematic Magmatism of the Central Finland Granitoid Complex II; Sources and Magmatic Evolution

The 1·88–1·87 Ga post-kinematic granitoidsof the Central Finland Granitoid Complex (CFGC) provide a keygeochemical link to understanding granite formation in Paleoproterozoicorogenic and post-orogenic terrains. Thickness of the crustand intra-crustal differentiation processes played an importantrole in the formation of three granitoid types that shortlyfollowed the peak of the Svecofennian orogeny. In the easternCFGC, pyroxene-bearing plutons with C-type geochemical affinitiespredominate. These were formed from a mixture of low- to moderate-degreepartial melts (30%) of mafic mantle-derived (basaltic, 49% SiO₂)source rocks and partial melts of pre-existing mafic granulitelower crust at depth. In the western CFGC, high-silica, iron-rich,fluorite-bearing plutons with A-type granite characteristicspredominate. A higher thermal gradient, thinner upper and lowercrust, and significantly more shallow Moho depth resulted inhigher proportions of crustal melts (0·3–0·4vs 0·1–0·2 in the eastern CFGC) incorporatedinto the partial melts of a mafic mantle-derived source. A geochemicalmodel focusing on the Jämsä and Honkajoki plutonsof the post-kinematic suite is presented, constraining the natureof the source rock(s), the degree of partial melting, proportionsof partial melts and fractionation processes involved. KEY WORDS: magmatic evolution; geochemistry; Proterozoic; granite; Finland     

Fuzzy information representation and processing in conventional GIS software: database design and application

Currently used methods for representing geographical information are inadequate because they do not tolerate imprecision. This leads to information loss and inaccuracy in analysis. Such expressive inadequacy is largely due to the underlying membership concept of classical set theory. To improve information processing in GIS research and application, an alternative membership concept is required. In this paper, we explore the inadequacy imposed upon geographical information representation by classical set theory and address the problems of information loss. A fuzzy relational data model is defined which is more representative for geographical information. A GIS database for agricultural land resource management is created by using the data model and a new technique for assessing land suitability is developed. The fuzzy representation largely facilitates data analysis in this GIS. The methods are tested with data from North Java, Indonesia using a vector-based GIS software package, Arc Info, and the analysis results are presented.     

New insights into Holocene atmospheric circulation dynamics in central Scandinavia inferred from oxygen‐isotope records of lake‐sediment cellulose

St. Amour, N. A., Hammarlund, D., Edwards, T. W. D. & Wolfe, B. B. 2010: New insights into Holocene atmospheric circulation dynamics in central Scandinavia inferred from oxygen‐isotope records of lake‐sediment cellulose. Boreas, Vol. 39, pp. 770–782. 10.1111/j.1502‐3885.2010.00169.x. ISSN 0300‐9843 Cellulose‐inferred lakewater oxygen‐isotope records have been obtained from two hydrologically open basins (Lake Spåime and Lake Svartkälstjärn), located on a west–east transect across central Sweden, to investigate changes in atmospheric circulation patterns during the Holocene. The Lake Spåime δ¹⁸O record is sensitive to changes in the seasonal distribution of precipitation in the Scandes Mountains of west‐central Sweden, and thus generally portrays variations in δ¹⁸O of precipitation (δ¹⁸O_P) that are governed predominantly by the influence of air masses originating from the North Atlantic. In contrast, the Lake Svartkälstjärn δ¹⁸O record appears to reflect the varying influence of air masses delivering moisture from the North Atlantic and the Baltic Sea. A comparison of inferred changes in δ¹⁸O_P over the Holocene between the two sites reveals systematic patterns of variability over widely different time scales. These include: (1) a previously recognized long‐term regional decline in δ¹⁸O_P, possibly in response to the declining vigour of Northern Hemisphere atmospheric circulation related to decreasing summer solar insolation; (2) newly identified inverse centennial‐ to millennial‐scale δ¹⁸O_P fluctuations at the two sites that may be linked to changes in modes of atmospheric circulation analogous to those described at interannual to multidecadal time scales by the North Atlantic Oscillation (NAO) index; and (3) a prolonged interval of apparent climatic stability in the mid‐Holocene (c. 6300–4200 cal. yr BP) characterized by persistently negative NAO‐like circulation.     

Apartheid spatial engineering and land use change in Mankweng, South Africa: 1963–2001

Land use change studies permeate the geographic literature. While these studies have helped researchers understand the dynamics and importance of such changes, they have less often taken a deeper historical approach in combination with their traditional strengths of geographic information analysis. In this study, we explore historical land use changes in one of South Africa's former bantustans, Lebowa, from 1963 to 2001. We argue that changes in land use arise from both current socioeconomic dynamics but also from historical precedent established by the apartheid regime. Our methods couple historical aerial photography to recent household surveys to elucidate the national, regional and local influences over land use change. We conducted extensive field research in the study site between 2003 and 2006. Our findings show a high degree of urbanization, a loss of grassland and agricultural land and a dramatic pattern of increasing spatial concentration near growth points. We outline three recommendations for policymakers planning post-apartheid rural spaces and conclude with future research needs.     

Investigation of high-level glaciofluvial terraces and re-evaluation of the established soil stratigraphy for Early and Middle Pleistocene surfaces, central Yukon, Canada

Palaeosols developed on the highest Yukon River glaciofluvial terraces were investigated in order to reconstruct the Plio-Pleistocene evolution of the river valley beyond Late Pleistocene glacial limits. A record of at least two pre-Reid (> 311 kyr) glaciations is chronicled by the presence of two populations of glaciofluvial terraces within the study area. The populations of pre-Reid terraces were identified based on their degree of soil development and elevation. Pre-Reid terraces 200–250 m above river level have preserved morphological and mineralogical features of the Wounded Moose palaeosol, a palaeosol previously associated with pre-Reid surfaces in central Yukon. Clay mineralogy and colour indicate that the Wounded Moose palaeosol developed in part during warm and sub-humid as well as temperate and humid interglacials. A second set of pre-Reid terraces between 110 and 30 m above river level are characterized by the presence of the less-developed Diversion Creek palaeosol, a palaeosol previously associated with only Reid-aged (< 311 kyr) surfaces in central Yukon. In contrast to the Wounded Moose palaeosol, the Diversion Creek palaeosol developed during comparatively cool and humid interglacial conditions. The presence of Diversion Creek palaeosols on pre-Reid outwash terraces suggests that a transition from dominantly warmer to cooler interglacial conditions occurred prior to 311 kyr in Yukon Territory. In addition, the presence of a Diversion Creek palaeosol cannot be used to differentiate stable Reid and stable pre-Reid surfaces across central Yukon.