Late Pleistocene stratigraphy at Boliden, northern Sweden

Till-covered sand and silt sediments with organic material from Boliden, northern Sweden, have been resampled and reinvestigated. Texture and petrographic analyses demonstrated one till bed overlying, and one underlying the sandy sediments. Low frequencies of diatoms were noted, representing freshwater, halophilous and brackish water taxa. The diatoms may be allochthonous or autochthonous, or redeposited from older deposits. Pollen analysis revealed a new picture of the composition of the vegetation, as compared with earlier investigations. The flora consisted of an arctic-subarctic treeless shrub and herb vegetation dominated by Salix, Betula nana , Gramineae and Cyperaceae. Artemisia and several arctic-alpine herbs were important elements. The identification of Salix wood as well as fruits and fruit scales of Betula nana and Betula cf. humilis is in agreement with the pollen-analytical results, as is the occurrence of Nordicboreal species of Coleoptera. Two radiocarbon datings resulted in an age of c. 45,000 B. P. and >40,000 B.P. The Boliden till-covered sediments were most probably deposited during an Early or Middle Weichselian interstadial, but the initial or final stage of an interglacial (Eemian) is also possible.     

La Malbaie Structure,Quebec—A Palaeozoic Meteorite Impact Site

Abstract Evidence in support of an origin by meteorite impact has been found at La Malbaie structure, 105 km northeast of Quebec City on the north shore of the St. Lawrence River. The structure has a central peak (Mont des Eboulements) 2500 feet (780 meters) above sea level, surrounded by lower hills and a semicircular valley with a diameter of 35 km. The circularity is incomplete as the peripheral valley terminates to the south and east at the St. Lawrence River which obscures an estimated 40 per cent of the crater. Rocks within the crater comprise charnockitic and granitic gneisses, anorthosite and gabbro of Precambrian Grenville age, and Middle Ordovician limestone.     

The origin and diagenesis of cherts from Cyprus

The Troodos Massif of Cyprus is overlain by a variety of cherts in pelagic chalks, volcanogenic sediments, radiolarites and radiolarian mudstones, all of Campanian to Upper Eocene age. There are two chert types, granular chert and vitreous chert. X-ray diffraction (XRD) reveals the silica polymorphs, disordered cristobalite and quartz. Silicification of the chalks varies from incipient, to bedded, granular cherts, all with disordered cristobalite as the main silica phase. Quartzitic cherts are restricted to the base of Upper Palaeocene and Lower Eocene calciturbidite beds. Disordered cristobalite predominates in the radiolarian mudstones at the foot of the sequence. The form of disordered cristobalite in cavities ranges from microspherules of radiating bladed crystals, the ‘lepispheres’ of the Deep Sea Drilling Project (DSDP) to bladed overgrowths, and fibrous silica. In contrast, within the fine grained matrix, the disordered cristobalite takes the form of partly coalescent crude microgranules and microspherules. Most of the chalcedonic quartz in Cyprus is derived by recrystallization of previously inorganically precipitated disordered cristobalite rather than by direct precipitation. According to the concept of impurity-controlled maturation the composition of host sediment controls the incorporation of exchangeable cations and other impurities into inorganically precipitated disordered cristobalite. With time (up to 100 million years) internal solid state reorganization of the disordered cristobalite is accompanied by gradual expulsion of impurities, until the cristobalite dissolves followed by quartz precipitation. Complete conversion to quartz takes place first in porous calcareous sediments free of impurities, as in the Cyprus calciturbidites; in fine grained clay-rich sediments, like Cyprus radiolarian mudstones, disordered cristobalite persists much longer. Impurity-controlled maturation also helps explain the diagenesis of Cyprus chert nodules.     

Rural Self-Reliance in Bondolfi, Zimbabwe: the role of beekeeping

Community-based economic self-reliance has become critical in many African countries because of the severity of prevailing soci-economic and environmental constraints. Concerns over food security have encouraged a re-evaluation of the importance of indigenous technical knowledge. This study examines a rural area in Zimbabwe where members of the local community have established a successful beekeeping association to improve their livelihoods. The history of the initiative, its broader impact on the community and the role played by external facilitation feature in the study.     

Views and Visions of Land Use in the United Kingdom

As part of a national study aimed at surveying the land use and landscape of the United Kingdom, 1287 surveyors recorded their views and visions of one-kilometre grid squares in which they conducted fieldwork. This study, which took place in 1996, has links to previous national land-use surveys by L. Dudley Stamp (1950) and Alice Coleman (1976, 1977). Of the total sample, 1037 reports are from the observations of school children. Their views relate to six key questions which have been analysed using qualitative research techniques to identify categories of shared responses. Reported in frequency counts, the results highlight a degree of communality in the perceptions of the majority of young people and adults involved. They show their hopes and dreams for a cleaner and varied landscape in the future with more green space, greater provision for well-planned low density housing, and recreation facilities. At the same time their expressed concerns for the management of the environment, housing development, green space provision, recreation and leisure activities indicate a disquiet about the future. This apparent pessimism is most notable in the views for urban locations. For rural locations there is a higher expectation that things will remain more-or-less the same in 20 years time.     

Pleistocene stratigraphy in the Dellen region, central Sweden

Robertsson, A.-M., Svedlund, J.-O., Andrén, T. & Sundh, M. 1997 (September): Pleistocene stratigraphy in the Dellen region, central Sweden. Boreas, Vol. 26, pp. 237–260. Oslo. ISSN 0300–9483. The Pleistocene stratigraphy in the Dellen region, central Sweden was studied using field observations made during mapping of Quaternary deposits and fabric analyses in excavated sections. The lithostratigraphy was also studied by seismic refraction measurements, analyses of grain-size distribution and organic carbon content. Biostratigraphical methods applied were pollen and diatom analyses. A general outline of the Pleistocene stratigraphy in the area is presented. Three different till beds are identified, the lowermost suggested to have been deposited during the Saalian glaciation and the other two during the Weichselian glaciation. According to the interpretation of the stratigraphy, it is questioned whether the first Weichselian ice sheet did in fact reach the Dellen area. A clayey sediment sequence at Norra Sannas accumulated during an interglacial, probably the Eemian. Most of the interglacial vegetation succession is reflected in the identified pollen flora. An initial phase with a light-demanding forest of Belula and Pinus was followed by immigration of Alnus, Picea and scattered occurrences of Corylus. A freshwater diatom flora was identified dominated by plankton taxa, e.g. Aulacoseira italica, A. distans and Cyclotella spp. In the lower part of the sequence a brackish-marine flora was registered, representing accumulation in a bay of the Eemian Sea. Fine-grained sediments at the Sundson and Vastansjd sites are interpreted as rebedded Eemian sediments according to the pollen flora. An (Early Weichselian) interstadial age is suggested for sediments found at Bjuraker. Dating by the ¹⁴C- and OSL methods was carried out on the interglacial and interstadial sediments, respectively. The ages range from approximately 19000 to 92000 BP. Correlation of interglacial vegetation history with central Finland and other areas is discussed.     

Upper Cretaceous Muti Formation: transition of a Mesozoic nate platform to a foreland basin in the Oman Mountains

The Upper Cretaceous (Turonian-Campanian) Muti Formation (Sayja Member) documents the transition from a passive continental margin to a foreland basin, related to overthrusting of continental margin and ophiolitic nappes derived from the Tethys ocean. Upper Cretaceous northeastward subduction culminated in collision of a trench with the Arabian margin. As the trench docked with the margin the lithosphere was flexed, forming a peripheral bulge that migrated cratonward with time. The platform edge was initially uplifted (Turonian) and deeply eroded, creating the ‘Wasia-Aruma break’. After passage of the peripheral bulge subsidence began, with accumulation first of ferruginous crusts on hardgrounds. Lime-muds were then deposited on a deepening unstable sea-floor, along with phosphatic nodules and crusts (Turonian-Coniacian). Passage of the overthrust load over the Arabian continental-margin edge downflexed the lithosphere (Santonian-Campanian), resulting in drastic foundering of the old shelf edge to form a foredeep. Upper platform horizons collapsed as slump-sheets and debris-flows. Limestone blocks and lithoclastic debris-flows were shed by mass-wasting of the already deeply eroded old platform edge. Mud and silt were derived from the uplifted Arabian continent and deposited by mainly gravitational processes in a foredeep below the C.C.D. Subsidence of the Arabian platform edge allowed the Semail ophiolite nappe finally to override the Muti basin (late Campanian) with little internal deformation. Submarine emplacement is suggested by the absence of ophiolitic detritus in the Muti Formation. The stratigraphic evolution of the Muti Formation is in good general agreement with a model of the transition of an old, thermally mature, passive continental margin to a foreland basin, where the emplaced load is submerged.     

A GIS for desert locust forecasting and monitoring

Abstract

Desert locust plagues can affect up to 20 per cent of the surface of the Earth. Data on locust breeding, environmental conditions and swarm movements in affected countries, are collected at the headquarters of the U.N. Food and Agriculture Organization in Rome. GIS technology coupled with remote sensing inputs allows these data to be utilised for monitoring and forecasting purposes much more effectively than heretofore. Design requirements and the implementation strategy for such a GIS are examined, emphasizing the role of global digital map datasets such as the Digital Chart of the World, the importance of effective data integration and the need for an ergonomic user interface that facilitates both data capture and analysis.     

A Late Pleistocene sequence at Margreteberg, southwestern Sweden

At Margreteberg, southwestern Sweden, a comple Pleistocene sequence has been stratigraphically investigated. Strata of clay, silt, sand, peat and solifluction layers are overlain by till-like sediments which are covered by sandy-clayey strata. By means of biostratigraphical analyses (foraminifera, olluscs, wood remains, pollen and diatoms), a reconstruction of the palaeoenvirnmental development has been obtained. Radiocarbon measurements and amiono acis ratios have been carried out in order to date the sediments. The foraminifera in the lowermost clay strata indicate Arctic or boreal-Arctic marine environment during the Late Saalian or Late Elsterian perods The δ¹⁸ Ovalues and molluscs also suggest that the clay was deposited in glaciomarine conditions. Amino acid ratios (D/L=0.25) of Hiatella in the clay imply an age between the Holsteinian and Eemian Interglacials. Teh peat layers contain a pollen flora. Prtedominated by Picea and Pinus, and are pollen analytically dated to the end of the Eemian interglacial. The solofluction sediments most probably were fromed during the first stage (s) of the Early weichselian and may include the initaial phase of the Brorup Interstadial (the Rodebaek interstadial). During this stage(s) aretic-Subarctic conditions previaled reflected by a pollen flora with a predominance of herbs and shrubs. Acidophilous and aerohpilous diatoms indicate oligotrophic shallow wate conditions in an Arctic environment, when almost no leaching of mineral solis occurred. The solofluction sediments also contain reworked interglacial (Eemian) pollen and brackish-Marine diatoms. Radiocarbon dating of the peat, wood and solofluction sediments yieded infinnite ages>40,000B.P.