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1.
Worm‐like trace fossils, sometimes of large size, have regularly been reported from the otherwise generally poorly‐fossiliferous Permo‐Triassic continental red beds of the East Devon coast, southwest England. Selected examples are discussed here to outline the difficulties involved in elucidating the true producers of these burrows and interpreting their significance in the local palaeoenvironment. 相似文献
2.
Eric F. Freeman 《Geology Today》2017,33(3):108-113
The ‘Maresfield Map’ is a map that purports to show features pertinent to the old iron industry in the Sussex Weald of southern England in 1724. It first appeared in a journal published by the Sussex Archaeological Society in early 1913, at roughly the same time as the formal publication by the Geological Society of London of papers introducing the discovery of the ‘remains’ of what became known as ‘Piltdown Man’ to the world. Piltdown Man was eventually revealed as fraudulent in 1953, followed by the Maresfield Map in 1974. Experiments in replication now show that the Maresfield Map is a sort of ‘treasure map’ (in a negative sense), which points fairly accurately to the supposed find‐spot of Piltdown Man, along with a coded accusation against Charles Dawson. The map's compiler is thought to have been L.F. Salzmann, the editor of the journal in which the map appeared. As such, the map represents the only such denunciation to have been published in the open literature in Dawson's lifetime, albeit a cryptic one. Mr Salzmann's possible motives are explored. 相似文献
3.
Felix V. Kaminsky Sergei M. Sablukov Ludmila I. Sablukova Dominic M.DeR. Channer 《Lithos》2004,76(1-4):565-590
In Venezuela, kimberlites have so far only been found in the Guaniamo region, where they occur as high diamond grade sheets in massive to steeply foliated Paleoproterozoic granitoid rocks. The emplacement age of the Guaniamo kimberlites is 712±6 Ma, i.e., Neoproterozoic. The Guaniamo kimberlites contain a high abundance of mantle minerals, with greater than 30% olivine macrocrysts. The principal kimberlite indicator minerals found are pyrope garnet and chromian spinel, with the overwhelming majority of the garnets being of the peridotite association. Chrome-diopside is rare, and picroilmenite is uncommon. Chemically, the Guaniamo kimberlites are characterized by high MgO contents, with low Al2O3 and TiO2 contents and higher than average FeO and K2O contents. These rocks have above average Ni, Cr, Co, Th, Nb, Ta, Sr and LREE concentrations and very low P, Y and, particularly, Zr and Hf contents. The Nb/Zr ratio is very distinctive and is similar to that of the Aries, Australia kimberlite. The Guaniamo kimberlites are similar in petrography, mineralogy and mantle mineral content to ilmenite-free Group 2 mica kimberlites of South Africa. The Nd-Sr isotopic characteristics of Guaniamo kimberlites are distinct from both kimberlite Group 1 and Group 2, being more similar to transitional type kimberlites, and in particular to diamondiferous kimberlites of the Arkhangelsk Diamond Province, Russia. The Guaniamo kimberlites form part of a compositional spectrum between other standard kimberlite reference groups. They formed from metasomatised subcontinental lithospheric mantle and it is likely that subduction of oceanic crust was the source of this metasomatised material, and also of the eclogitic component, which is dominant in Guaniamo diamonds. 相似文献
4.
Tunnel excavation is a coupled three-dimensional problem dealing with two different structures: lining and rockmass. For a simple application it is useful to develop simplified methods by treating the problem as plane strain. If the problem of tunnel face advance presents an axisymmetric geometry, then we show that the major parameter governing the ground–interface–lining interaction is the convergence of the tunnel U0 at the moment of the lining installation. The ‘New Implicit Method’ (NIM) presented in this paper makes use of principles similar to those of the ‘convergence–confinement’ method, but it provides a better appreciation of the coupled behaviour of rockmass and lining. For independent time constitutive laws (elasticity and plasticity), we point out that the convergence U0 depends not only on the mechanical behaviour of the rockmass and on the distance from the tunnel face, as predicted by the ‘convergence–confinement’ method, but also on the stiffness of the lining previously set. We present the ‘NIM’ for elastic and perfect elastoplastic rockmasses without dilatancy for many criteria. The development of this new method is based on the results of tunnel calculations with an axisymmetric FEM numerical model that takes into account the three-dimensional aspect of the problem. Using this method is simple and its results agree well with the FEM numerical results. Its accuracy is highly satisfactory for a geotechnical study. 相似文献
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6.
Barry Jay Katz 《Organic Geochemistry》1983,4(3-4)
Laboratory experimentation on whole-rock ‘Rock-Eval’ pyrolysis has shown that the characterization of organic matter through the use of a modified van Krevelen diagram, in which the hydrogen and oxygen indices are substituted for the atomic H/C and O/C ratios, produces questionable results. The hydrogen and oxygen indices have been found to be strongly affected by both matrix mineralogy and level of organic enrichment. It appears, therefore, that although the modified van Krevelen diagram maybe useful for tracing evolutionary pathways as organic matter matures, it can be very misleading when used to assess kerogen type. 相似文献
7.
This paper questions Geographers debates about ‘caring at a distance’ and the ‘geographies of responsibility’, focussing on the treatment of the theme of partiality in ethics and justice. Debates in Geography often present partial commitments as morally or politically problematic on the grounds that they prioritize self-interest, exclusionary, and geographically restricted ways of relating to others. We outline how debates about caring at a distance and the geographies of responsibility frame partiality as a problem to be overcome. We argue that Geography’s engagements with moral philosophy are premised on faulty assumptions about the sorts of influences people are liable to act upon (one’s that privilege causal knowledge as the primary motivating force), and also flawed assumptions about the sorts of problems that academic reasoning about normative issues is meant to address (the assumption that people are too egoistical and not altruistic enough). We use the theme of generosity as an entry point to argue that partiality and finitude might be the conditions for any ethical–political project that de-centres the motivation of practical action away from the sovereign self towards responsive and attentive relations of encounter with the needs of others. Understanding generosity as a modality of power suggests a revised programme for geographical investigations of the intersection between ethics, morality and politics: one which looks at how opportunities to address normative demands in multiple registers are organized and transformed; at the ways in which dispositions to respond and to be receptive to others are worked up; and how opportunities for acting responsively on these dispositions are organized. 相似文献
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Craig D. Barrie 《Geology Today》2010,26(1):28-33
Pyrite (FeS2 ) is the most abundant sulphide mineral in the Earth's crust, and with its characteristic shape and appearance, is easily one of the most recognizable. Yet, pyrite has a somewhat tarnished reputation with many considering it to be waste material and of little economic importance, never-mind interest. This assessment however, is misleading and a considerable volume of current research focuses upon the unique characteristics and formation of pyrite. Indeed, with its potential for revealing the very foundations of life, as well as maximizing the discovery and exploitation of society's future metallic resources, pyrite may be of much greater interest and benefit than many geologists realize. 相似文献
10.
Giancarlo Gioda 《国际地质力学数值与分析法杂志》1982,6(1):21-46
An analysis is presented of the non-linear creep effects around a deep circular tunnel driven in ‘squeezing’ ground. The time-dependent behaviour of the geotechnical medium is described by means of a simple viscoplastic rheological model capable of approximating primary, secondary and tertiary creep behaviours. It is shown that tertiary creep can be allowed for by providing a suitable law governing the variation of some material parameters (such as viscosity) with stresses and strains. The basic operations of the ‘evolutive’ procedure adopted for time integration are outlined. Along each time integration step, quadratic variations of the stress and strain fields and linear variations of the material parameters are assumed. The results of various finite element analyses are presented concerning both lined and unlined cases. For the lined cases, the influence of the liner stiffness and of the time elapsed between the end of excavation and the liner installation is considered. 相似文献
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JOSEPH R. FELDKAMP 《国际地质力学数值与分析法杂志》1996,20(11):815-830
An isothermally heated, impervious cylinder, which is placed normal to the path of flowing groundwater, is theoretically evaluated for its potential to serve as a kind of ‘groundwater velocimeter’. The essential task is to determine whether the variation in heat output along the cylinder perimeter is sufficiently large to permit measurement for typical groundwater velocities. Using finite elements, the governing equations of advective thermal transport in saturated porous media are solved to obtain the variation in heat output along the circumference of the heated cylinder. An annular region of different hydraulic conductivity is assumed to separate the cylinder from the surrounding formation. The creation of such a region during placement of a cylinder is inevitable. A parametric study led to the following conclusions: (1) A smaller cylinder radius is preferable since the time to achieve a particular degree of asymmetry in heat output is then greatly reduced. (2) An annular region of lower hydraulic conductivity, relative to formation, reduces output asymmetry by no more than 25%, but if hydraulic conductivity is increased, output asymmetry can increase several times. (3) For annular regions having a higher hydraulic conductivity than the surrounding formation, annular thickness is not important. (4) The least groundwater speed which may be accurately measured by such a device will depend heavily upon instrumentation but is tentatively placed at about 5⋅0×10−5 cm/s. Theoretical results are approximately confirmed by preliminary experiments with a prototype device which has been constructed so as to directly measure the expected variation in thermal output. Partial construction details are provided. 相似文献
13.
H. Nonn 《Geoforum》1975,6(2)
At least in France the sub-region is a living spatial entity. It is partly the heir of structures established in the pre-industrial epoch, receiving from the ancient ‘pays’ and old administrative structures the sense of belonging to a certain social cadre held by a population. For a long period the weak development of an hierarchy of urban services made most towns of equal standing, limiting the growth of commercial relationships and the dimensions of functional spaces. With the growth of an hierarchy of urban services, and improvement in accessibility the functional units have enlarged, breaking unequally the former cadres, and creating polarisations of various scales. Where the metropolises have not become dominant the sub-regions remain sufficiently autonomous, around a town of medium size. More often, in every case where local polarisations have been progressively effaced, and economic spaces have enlarged immeasurably and where the administrative region is seeking identity, the sub-region is reasserted as a social functional space in the pattern of customary life-style, and appears acceptable as a level in the operation of spatial management. 相似文献
14.
Howard Falcon‐Lang 《Geology Today》2012,28(1):26-30
The British Geological Survey is home to more than three million fossils collected over two centuries and catalogued with enormous precision. However, as generations of curators have come and gone, a few collections have lain forgotten and their significance has gradually passed out of memory. Six months ago, I pulled opened some drawers marked ‘unregistered fossil plants’ in one of the Survey's windowless vaults in Keyworth, in central England. What I found inside made my jaw drop. Contained within were hundreds of beautiful thin sections of fossil wood dating from the early nineteenth century. The collection was assembled by botanist Joseph Hooker (Darwin's best friend) while he was briefly employed by the Survey in 1846. The material includes some of the first thin sections ever made by William Nicol, the pioneer of petrography, in the late 1820s, as well as specimens picked up by Darwin and Hooker on their round‐the‐world voyages in the 1830s and 1840s. The collection is particularly interesting in the way it sheds light on the vibrant and sometimes murky world of early nineteenth century science. This is the story of these fascinating fossils. 相似文献
15.
G. Beer 《国际地质力学数值与分析法杂志》1983,7(1):1-7
The Finite Element Method is frequently used to analyse problems involving an ‘infinite domain’. A typical problem is an underground excavation in prestressed infinite medium in either tunnelling or mining operations or a foundation in an infinite half space. This paper examines the implications of mesh truncation on the accuracy of the accuracy of the solution. At the same time, a more economical and accurate method of analysing these problems using special ‘infinite domain’ Finite Elements is presented. 相似文献
16.
The renewed investigations of the Benot Ya'aqov site resulted in the discovery of a bar-like depositional structure located on the eastern bank of the Jordan River (southern Hula Valley, Israel). Its interdisciplinary study resulted in the identification of four lithofacial fluvial units, all tilted (20–25 degrees dip) and all containing archaeological and paleontological finds. The structure, caused by diverse resistance of the local lithology and tectonic activity, is assigned to the Benot Ya'aqov Formation. The material culture is assigned to the Acaheulian Industrial Complex and is indicative of a continuous occupation of the Benot Ya'aqov embayment during Middle Pleistocene times. 相似文献
17.
Here we briefly report on the discovery of a new Fossil‐Lagerstätte locality, Owadów‐Brzezinki quarry (central Poland), which exposes Late Jurassic (Late Tithonian) carbonate sediments with an extremely fossiliferous horizon of lithographic‐type limestones. Numerous specimens of horseshoe crabs were found in association with an enormously rich assemblage of the soft‐shelled bivalves Corbulomima obscura and Mesosaccella sp., the remains of various fishes and marine reptiles, rare ammonites, crustaceans, land insects and pterosaurs. The uniqueness of this new locality lies in its very close stratigraphical relationship to one of the most famous Fossil‐Lagerstätte localities in the world—Solnhofen, in southern Germany, with approximately 2 Ma separating them. Marine and terrestrial creatures lived and died during the Late Jurassic both at Solnhofen (Hybonotum Zone) and in another area (Owadów‐Brzezinki quarry, Zarajskensis Subzone), under closely related environmental conditions. The small palaeogeographical distance separating these two locations enables, for the first time, an effective palaeobiological test of the pace of evolutionary speciation amongst different groups of organisms. 相似文献
18.
The paper deals with the analysis of excavations which are very long and can, for all practical purposes, be considered to be infinitely long. Special infinite finite and boundary elements are developed for the modelling of the infinitely long part of such excavations. Test examples are presented which show the accuracy which can be obtained by using these elements. Finally, examples of application in mining and petroleum engineering are shown. 相似文献
19.
Stephen E. Grasby Ruth Bezys Kathleen L. Londry 《Journal of Geochemical Exploration》2006,89(1-3):149
Siliceous ‘solution chimneys’are described from a region unaffected by volcanism or high temperature fluid flow. The features are interpreted as low temperature dissolution/replacement structures formed in Paleozoic carbonates. The features are thought to be paleo-brine spring discharge sites similar to modern springs found within the same area which host a mid-continent marine ecosystem. Geochemical modeling shows mixing of spring waters with shallow groundwater could generate conditions of undersaturation with respect to calcite and silica oversaturation. 相似文献
20.
Recent years have seen academic geographers engaged in a series of debates over the current state of the discipline, its ‘relevance’ to others in the social sciences, to policy-makers, and to those studying geography at school age. This short critical review builds upon an issue raised in this journal [Thrift, N., 2002. The future of geography. Geoforum 33, 291–298], namely the role of geographers as public intellectuals. After reviewing the different ways in which the notion of public intellectuals has been understood, the paper turns to geography’s representations and to its publics. The paper concludes by arguing for an appreciation of the full range of ways in which geographers call forth publics through a range of representational strategies. It suggests that regardless of how geographers perform publicly and intellectually, two things are perhaps worth remembering: it is in the interest of geographers to name what they do as geography and to name themselves as geographers. 相似文献