Die Flußspatlagerstätten Asturiens/Nordspanien und deren Genese     

Prof. Dr. Anton Forster 《International Journal of Earth Sciences》1974,63(1):212-263

The fluorspar deposites described are located within the permotriasic basin of Western Asturias/Northern Spain. The block-faulted basin is bordered in the south by the Cantabrian Mountainrange, folded in Hercynian times. The fluorspar deposites overlie the strata of this paleozoic base and the fluorspar-layers dip gently to the North at 10 to 15?. They are related to the angular unconformity between the mostly eroded Paleozoic rocks and the overlying, mainly red, Permotriasic sediments. Volcanic rocks apear only in few places, where they are intercalating more ore less the upper parts of triasic strata, reddish shales of “Keuper” age. The occurrences fluorspar-layers are found mainly in the uneroded areas where the basal Permotriasic is still preserved on the old Permian land surface, underlain preserved on the old Permian land surface, underlain mostly by Devonian and lower Carboniferous limestones, marls and shales. A special rock type, a breccia between the foulded Paleozoic base and the unfolded Permotriasic sediments forms a marker horizon, thought to have originated from the fracturing of the underlaying Paleozoic rocks. The genesis of fluorspar and breccia is thought to be connected with the formation of a peneplain-like land surface and its repetated uplift and depression, i. e. repeated flooding by sea and subsequent emergence. Light-grey to reddisch sand- and siltstones as well as small pebble conglomerates were deposited in erosion channels and karst holes, sometimes extending through the breccia down into the massiv lower Carboniferous and Devonian base. It is in these sediments, that the fluorspar is found to produce dispersed or in massiv form sheet-like and flat-lying bodies as well as channel-like, occurrences. In areas of strong post, Permian tectonic movements the stratabound mineralisation were sometimes mobilized to form dike-like deposites. The morphological and petrological structure, e. g. the complete lack of primary zoning even in dike-like deposites, and the geological situation as a whole contradict the opinion of G.Einecke (1956) that these fluorspar deposites originated from hydrothermal solutions, emanating from plutonic or volcanic rocks. Geochemical investigations of soil samples and drill cores from Paleozoic rocks point to the origin of fluorine from Devonian and Carboniferous, rich in organisms (Coal-strata) and consisting of shales marls and limestones (or even older rocks) which were eroded and redeposited in Permian times.  相似文献   

Functional Performance of Three Invasive <Emphasis Type="Italic">Marenzelleria</Emphasis> Species Under Contrasting Ecological Conditions Within the Baltic Sea     

Cintia O. Quintana  Caroline Raymond  Francisco J. A. Nascimento  Stefano Bonaglia  Stefan Forster  Jonas S. Gunnarsson  Erik Kristensen 《Estuaries and Coasts》2018,41(6):1766-1781

A 4-week laboratory experiment investigated the behaviour (survival and bioirrigation) and impact of the invasive polychaetes Marenzelleria viridis, M. neglecta and M. arctia on sediment-water solutes exchange, porewater chemistry, and Fe and P interactions in high-salinity sandy sediment (HSS) and low-salinity muddy sediment (LSM) from the Baltic Sea. M. viridis showed deep burrowing with efficient bioirrigation (11 L m^?2 day^?1) and high survival (71%) in HSS, while M. arctia exhibited shallow burrowing with high bioirrigation (12 L m^?2 day^?1) and survival (88%) in LSM. M. neglecta behaved poorly in both ecological settings (bioirrigation, 5–6 L m^?2 day^?1; survival, 21–44%). The deep M. viridis bioirrigation enhanced total microbial CO₂ (TCO₂) production in HSS by 175% with a net efflux of NH₄⁺ and PO₄^3?, at rates 3- to 27-fold higher than for the other species. Although the shallow and intense bioirrigation of M. arctia in LSM stimulated microbial TCO₂ production to some extent (61% enhancement), the nutrient fluxes close to zero indicate that it effectively prevented the P release. Porewater Fe:PO₄^3? ratios revealed that the oxidizing effect of M. arctia bioirrigation increased the PO₄^3? adsorption capacity of LSM twofold relative to defaunated controls while no buffering of PO₄^3? was detected in M. viridis HSS treatment. Therefore, the different behaviour of the three species in various environments and the sharp contrast between M. viridis and M. arctia effects on C, N and P cycling must be considered carefully when the ecological role of Marenzelleria species in the Baltic Sea is evaluated.  相似文献   

Testing Nano-Powder and Fused-Glass Mineral Reference Materials for In Situ Rb-Sr Dating of Glauconite,Phlogopite, Biotite and Feldspar via LA-ICP-MS/MS     

Ahmad Redaa  Juraj Farkaš  Sarah Gilbert  Alan S. Collins  Stefan Löhr  Davood Vasegh  Marnie Forster  Morgan Blades  Thomas Zack  Andrea Giuliani  Roland Maas  Andre Baldermann  Martin Dietzel  Dieter Garbe-Schönberg 《Geostandards and Geoanalytical Research》2023,47(1):23-48

Reference materials (RMs) with well-characterised composition are necessary for reliable quantification and quality control of isotopic analyses of geological samples. For in situ Rb-Sr analysis of silicate minerals via laser ablation inductively coupled plasma tandem mass spectrometry (LA-ICP-MS/MS) with a collision/reaction cell, there is a general lack of mineral-specific and matrix-matched RMs, which limits wider application of this new laser-based dating technique to certain minerals. In this work, pressed nano-powder pellets (NP) of four RMs, GL-O (glauconite), Mica-Mg (phlogopite), Mica-Fe (biotite) and FK-N (K-feldspar), were analysed and tested for in situ Rb-Sr dating, complemented by isotope dilution (ID) MC-ICP-MS Rb-Sr analyses of GL-O and Mica-Mg. In addition, we attempted to develop alternative flux-free and fused ‘mineral glasses’ from the above RMs for in situ Rb-Sr dating applications. Overall, the results of this study showed that among the above RMs only two NP (Mica-Mg-NP and GL-O-NP) were suitable and robust for in situ dating applications. These two nano-powder reference materials, Mica-Mg-NP and GL-O-NP, were thus used as primary RMs to normalise and determine Rb-Sr ages for three natural minerals: MDC phlogopite and GL-O glauconite grains, and also Mica-Fe-NP (biotite). Our in situ analyses of the above RMs yielded Rb-Sr ages that are in good agreement (within 8%) of published ages, which suggests that both Mica-Mg-NP and GL-O-NP are suitable RMs for in situ Rb-Sr dating of phlogopite, glauconite and biotite. However, using secondary RMs is recommended to monitor the quality of the obtained ages.  相似文献   

Linking social drivers of marine debris with actual marine debris on beaches     

Slavin C  Grage A  Campbell ML 《Marine pollution bulletin》2012,64(8):1580-1588

The drivers (social) and pressures (physical) of marine debris have typically been examined separately. We redress this by using social and beach surveys at nine Tasmanian beaches, across three coastlines and within three categories of urbanisation, to examine whether people acknowledge that their actions contribute to the issue of marine debris, and whether these social drivers are reflected in the amount of marine debris detected on beaches. A large proportion (75%) of survey participants do not litter at beaches; with age, gender, income and residency influencing littering behaviour. Thus, participants recognise that littering at beaches is a problem. This social trend was reflected in the small amounts of debris that were detected. Furthermore, the amount of debris was not statistically influenced by the degree of beach urbanisation, the coastline sampled, or the proximity to beach access points. By linking social and physical aspects of this issue, management outcomes can be improved.  相似文献   

Characterizing supraglacial meltwater channel hydraulics on the Greenland Ice Sheet from in situ observations          下载免费PDF全文

Colin J. Gleason  Laurence C. Smith  Vena W. Chu  Carl J. Legleiter  Lincoln H. Pitcher  Brandon T. Overstreet  Asa K. Rennermalm  Richard R. Forster  Kang Yang 《地球表面变化过程与地形》2016,41(14):2111-2122

Supraglacial rivers on the Greenland Ice Sheet (GrIS) transport large volumes of surface meltwater toward the ocean, yet have received relatively little direct research. This study presents field observations of channel width, depth, velocity, and water surface slope for nine supraglacial channels on the south‐western GrIS collected between July 23 and August 20, 2012. Field sites are located up to 74 km inland and span 494–1485 m elevation, and contain measured discharges larger than any previous in situ study: from 0.006 to 23.12 m³/s in channels 0.20 to 20.62 m wide. All channels were deeply incised with near vertical banks, and hydraulic geometry results indicate that supraglacial channels primarily accommodate greater discharges by increasing velocity. Smaller streams had steeper water surface slopes (0.74–8.83%) than typical in terrestrial settings, yielding correspondingly high velocities (0.40–2.60 m/s) and Froude numbers (0.45–3.11) with supercritical flow observed in 54% of measurements. Derived Manning's n values were larger and more variable than anticipated from channels of uniform substrate, ranging from 0.009 to 0.154 with a mean value of 0.035 ± 0.027 despite the absence of sediment, debris, or other roughness elements. Ubiquitous micro‐depressions in shallow sections of the channel bed may explain some of these roughness values. However, we find that other, unobserved sources of flow resistance likely contributed to these elevated Manning's n values: future work should explicitly consider additional sources of flow resistance beyond bed roughness in supraglacial channels. We conclude that hydraulic modeling for these channels must allow for both subcritical and supercritical flow, and most importantly must refrain from assuming that all ice‐substrate channels exhibit similar hydraulic behavior, especially for Froude numbers and Manning's n. Finally, this study highlights that further theoretical and empirical work on supraglacial channel hydraulics is necessary before broad scale understanding of ice sheet hydrology can be achieved. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

The use of site investigation data for the preparation of engineering geological maps and reports for use by planners and civil engineers     

A. Forster  M.G. Culshaw 《Engineering Geology》1990,29(4):347-354

Forster, A. and Culshaw, M.G., 1990. The use of site investigation data for the preparation of engineering geological maps and reports for use by planners and civil engineers. Eng. Geol., 29: 347–354.

In modern cities hundreds of site investigations have been carried out before the construction of roads, offices, factories and housing estates. The results of these investigations represent a large resource of geological and geotechnical information worth millions of pounds. Much of this information is lost, or is not accessible, because of confidentiality; that which is available will be of variable content and quality. The geographical and stratigraphical distribution will also be uneven. However, maps, and resumés of the engineering behaviour of the geological materials in an area, can be produced to guide planners and to help engineers at the earliest stage of development.

In this paper the authors discuss the use of the data contained in site investigation reports to prepare engineering geological maps and illustrate this by reference to recent applied geological mapping projects carried out by the British Geological Survey.  相似文献   

Mapping diversified peri-urban agriculture – potential of object-based versus per-field land cover/land use classification     

Dionys Forster  Tobias Walter Kellenberger  Yves Buehler  Bernd Lennartz 《国际地球制图》2013,28(3):171-186

High spatial resolution satellite data contribute to improving land cover/land use (LCLU) classification in agriculture. A classification procedure based on Quickbird satellite image data was developed to map LCLU of diversified agriculture at sub-communal and communal level (7 km²). Segmentation performance of the panchromatic band in combination with high pass filters (HPF) was tested first. Accuracy of field boundary delineation was evaluated by an object-based segmentation, a per-field and a manual classification, along with a quantitative accuracy assessment. Sub-communal classification revealed an overall accuracy of 84% with a κ coefficient of 0.77 for the per-field vector segmentation compared to an overall accuracy of 56–60% and a κ coefficient of 0.37–0.42 for object-based approaches. Per-field vector segmentation was thus superior and used for LCLU classification at communal level. Overall accuracy scored 83% and the κ coefficient 0.7. In diversified agriculture, per-field vector segmentation and classification achieved higher classification results.  相似文献   

Aggradation and carbonate accumulation of Holocene Norwegian cold‐water coral reefs          下载免费PDF全文

Jürgen Titschack  Daniel Baum  Ricardo De Pol‐Holz  Matthias López Correa  Nina Forster  Sascha Flögel  Dierk Hebbeln  André Freiwald 《Sedimentology》2015,62(7):1873-1898

Cold‐water coral ecosystems present common carbonate factories along the Atlantic continental margins, where they can form large reef structures. There is increasing knowledge on their ecology, molecular genetics, environmental controls and threats available. However, information on their carbo‐nate production and accumulation is still very limited, even though this information is essential for their evaluation as carbonate sinks. The aim of this study is to provide high‐resolution reef aggradation and carbonate accumulation rates for Norwegian cold‐water coral reefs from various settings (sunds, inner shelf and shelf margin). Furthermore, it introduces a new approach for the evaluation of the cold‐water coral preservation within cold‐water coral deposits by computed tomography analysis. This approach allows the differentiation of various kinds of cold‐water coral deposits by their macrofossil clast size and orientation signature. The obtained results suggest that preservation of cold‐water coral frameworks in living position is favoured by high reef aggradation rates, while preservation of coral rubble prevails by moderate aggradation rates. A high degree of macrofossil fragmentation indicates condensed intervals or unconformities. The observed aggradation rates with up to 1500 cm kyr^?1 exhibit the highest rates from cold‐water coral reefs so far. Reef aggradation within the studied cores was restricted to the Early and Late Holocene. Available datings of Norwegian cold‐water corals support this age pattern for other fjords while, on the shelf, cold‐water coral ages are reported additionally from the early Middle Holocene. The obtained mean carbonate accumulation rates of up to 103 g cm^?2 kyr^?1 exceed previous estimates of cold‐water coral reefs by a factor of two to three and by almost one order of magnitude to adjacent sedimentary environments (shelf, slope and deep sea). Only fjord basins locally exhibit carbonate accumulation rates in the range of the cold‐water coral reefs. Furthermore, cold‐water coral reef carbonate accumulation rates are in the range of tropical reef carbonate accumulation rates. These results clearly suggest the importance of cold‐water coral reefs as local, maybe regional to global, carbonate sinks.  相似文献   

ELF rotating magnetic fields: Prenatal exposure and adult behavior     

Michael A. Persinger  William S. Forster IV 《Theoretical and Applied Climatology》1970,18(3-4):363-369

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Comparison of Models for Delineating Wellhead Protection Areas in Confined to Semiconfined Aquifers in Alluvial Basins   总被引：2，自引：0，他引：2  

Craig B. Forster  Thomas E. Lachmar  Douglas S. Oliver 《Ground water》1997,35(4):689-697

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