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Geological Data (geological + data)
Selected AbstractsA REVIEW OF GEOLOGICAL DATA THAT CONFLICT WITH THE PARADIGM OF CATAGENIC GENERATION AND MIGRATION OF OILJOURNAL OF PETROLEUM GEOLOGY, Issue 3 2005H. Hugh Wilson The majority of petroleum geologists today agree that the complex problems that surround the origin, generation, migration and accumulation of hydrocarbons can be resolved by accepting the geochemical conclusion that the process originates by catagenic generation in deeply-buried organically-rich source rocks. These limited source rock intervals are believed to expel hydrocarbons when they reach organic maturity in oil kitchens. The expelled oil and gas then follow migration pathways to traps at shallower levels. However, there are major geological obstacles that cast doubt upon this interpretation. The restriction of the source rock to a few organically rich levels in a basin forces the conclusion that the basin plumbing system is leaky and allows secondary horizontal and vertical migration through great thicknesses of consolidated sedimentary rocks in which there are numerous permeability barriers that are known to effectively prevent hydrocarbon escape from traps. The sourcing of lenticular traps points to the enclosing impermeable envelope as the logical origin of the trapped hydrocarbons. The lynch-pin of the catagenic theory of hydrocarbon origin is the expulsion mechanism from deeply-buried consolidated source rock under high confining pressures. This mechanism is not understood and is termed an "enigma". Assuming that expulsion does occur, the pathways taken by the hydrocarbons to waiting traps can be ascertained by computer modelling of the basin. However, subsurface and field geological support for purported migration pathways has yet to be provided. Many oilfield studies have shown that oil and gas are preferentially trapped in synchronous highs that were formed during, or very shortly after, the deposition of the charged reservoir. An unresolved problem is how catagenically generated hydrocarbons, expelled during a long-drawn-out maturation period, can have filled synchronous highs but have avoided later traps along the assumed migration pathways. From many oilfield studies, it has also been shown that the presence of hydrocarbons inhibits diagenesis and compaction of the reservoir rock. This "Füchtbauer effect" points to not only the early charging of clastic and carbonate reservoirs, but also to the development of permeability barriers below the early-formed accumulations. These barriers would prevent later hydrocarbon additions during the supposed extended period of expulsion from an oil kitchen. Early-formed traps that have been sealed diagenetically will retain their charge even if the trap is opened by later structural tilting. Diagenetic traps have been discovered in clastic and carbonate provinces but their recognition as viable exploration targets is discouraged by present-day assumptions of late hydrocarbon generation and a leaky basin plumbing system. Because there are so many geological realities that cast doubt upon the assumptions that devolve from the paradigm of catagenic generation, the alternative concept of early biogenic generation and accumulation of immature oil, with in-reservoir cracking during burial, is again worthy of serious consideration. This concept envisages hydrocarbon generation by bacterial activity in many anoxic environments and the charging of synchronous highs from adjacent sources. The resolution of the fundamental problem of hydrocarbon generation and accumulation, which is critical to exploration strategies, should be sought in the light of a thorough knowledge of the geologic factors involved, rather than by computer modelling which may be guided by questionable geochemical assumptions. [source] Determination of rock mass strength properties by homogenizationINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 13 2001A. Pouya Abstract A method for determining fractured rock mass properties is presented here on the basis of homogenization approach. The rock mass is considered to be a heterogeneous medium composed of intact rock and of fractures. Its constitutive model is studied numerically using finite element method and assimilating the fractures to joint elements (Coste, Comportement Thermo-Hydro-Mécanique des massifs rocheux fracturés. Thèse de Doctorat, Ecole Nationale des Ponts et Chaussées, Paris, 1997). The method has been applied to a granite formation in France. Geological data on different families of fractures have been used for the statistical representation of the fractures. A mesh-generating tool for the medium with high density of fractures has been developed. The mechanical behaviour of the rock mass (elasticity, ultimate strength and hardening law) has been determined assuming linear elasticity and Mohr,Coulomb strength criterion both for the intact rock and the fractures. Evolution of the mechanical strength in different directions has been determined as a function of the mean stress, thanks to various numerical simulations. The mechanical strength appears to be anisotropic due to the preferential orientation of the fractures. The numerical results allowed us to determine an oriented strength criterion for the homogenized rock mass. A 2D constitutive law for the homogenized medium has been deduced from numerical data. A 3D extension of this model is also presented. Copyright © 2001 John Wiley & Sons, Ltd. [source] Cretaceous,Tertiary geodynamics: a North Atlantic exerciseGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 3 2001Trond H. Torsvik Summary New reconstructions are presented for the Cretaceous,Early Tertiary North Atlantic using a combination of palaeomagnetic, hotspot and magnetic anomaly data. We utilize these reconstructions in an analysis of previously described misfits between the North Atlantic Plate elements at successive intervals during this time period. We are able to achieve reasonable overlap between the hotspot and palaeomagnetic reconstructions between 40 and 95 Ma and thus are able to support the idea that the Indo,Atlantic hotspots are relatively stationary. Small, but systematic discrepancies for this time interval can readily be modelled with a long-term, octopole non-dipole field contribution (G3 = g30/g10 = 0.08). However, hotspot and palaeomagnetic reconstructions for the Early Cretaceous North Atlantic show substantial differences that cannot be explained by constant, non-dipole fields and we favour an explanation for these discrepancies in terms of true polar wander (TPW) triggered by mantle instabilities between 125 and 95 Ma; this constitutes the only identifiable event of significant TPW since the Early Cretaceous. Taken in the context of available geochronological and geological data and seismic tomography from the region, the 95,40 Ma reconstructions and their time-consequent geological products are interpreted in terms of specific conditions of mantle-crust coupling and global plate motions/tectonic activity. Highlights from these reconstructions show uniform NE movement of the coupled North American, Greenland and Eurasian plates from 95 to 80 Ma; a marked cusp in the paths for all three elements at 80 Ma where the three plates simultaneously change direction and follow a uniform NW-directed motion until c. 20 Ma when Eurasia diverges NE, away from the still-NW-moving Greenland and North American elements. Positioning of the Iceland plume beneath the spreading-ridge at 20 Ma may have increased upwelling below the ridge, increased the ridge-push, and caused a NE shift in the absolute direction of Eurasia. [source] Shared near neighbours neural network model: a debris flow warning systemHYDROLOGICAL PROCESSES, Issue 14 2007Fi-John Chang Abstract The main purpose of this study is to develop a new type of artificial neural network based model for constructing a debris flow warning system. The Chen-Eu-Lan river basin, which is located in Central Taiwan, is assigned as the study area. The creek is one of the most well-known debris flow areas where several damaging debris flows have been reported in the last two decades. The hydrological and geological data, which might have great influence on the occurrence of debris flows, are first collected and analysed, then, the shared near neighbours neural network (SNN + NN) is presented to construct the debris flow warning system for the watershed. SNN is an unsupervised learning method that has the advantage of dealing with non-globular clusters, besides presenting computational efficiency. By using SNN, the compiled hydro-geological data set can easily and meaningfully be clustered into several categories. These categories can then be identified as ,occurrence' or ,no-occurrence' of debris flows. To improve the effectiveness of the debris flow warning system, a neural network framework is designed to connect all the clusters produced by the SNN method, whereas the connected weights of the network are adjusted through a supervised learning method. This framework is used and its applicability and practicability for debris flow warning are investigated. The results demonstrate that the proposed SNN + NN model is an efficient and accurate tool for the development of a debris flow warning system. Copyright © 2007 John Wiley & Sons, Ltd. [source] Micro-Raman spectroscopy of decorated pottery from the Iberian archaeological site of Puente Tablas (Jaén, Spain, 7th,4th century B.C.)JOURNAL OF RAMAN SPECTROSCOPY, Issue 1 2010D. Parras Abstract In this paper, Raman spectroscopy is used for the first time to identify the pigments on decorated antique Iberian pottery. Ceramic fragments of type Real and others from the archaeological excavation in the oppidum Puente Tablas were examined. Different types of iron oxide pigments (hematite and goethite) were identified, along with amorphous carbon. In some samples, the presence of chalk or gypsum could be demonstrated. Some unattributed Raman bands are believed to be associated either with post-burial organic deposition or with silicate materials that are present in red ochre. It was possible to relate the findings with geological data from the region and to make assumptions on a local production. Copyright © 2009 John Wiley & Sons, Ltd. [source] Modification of impact craters in the northern plains of Mars: Implications for Amazonian climate historyMETEORITICS & PLANETARY SCIENCE, Issue 10 2006M. A. Kreslavsky Two of the 130 craters have unusually rough ejecta; they are deep, have steep walls, and are apparently the youngest in the population. Icy mantles filling the local subkilometer-scale topographic lows is the main contribution to ejecta smoothing, which occurs at a time scale on the order of tens of Myr. Wall degradation and crater shallowing generally occur at longer time scales, comparable to the duration of the Amazonian period. Many craters are shallow due to filling of the crater with specific ice-rich material of uncertain origin. We use our collected data to infer the nature of the past climate back through the Amazonian, a period prior to ,10,20 Myr ago, when orbital parameter solutions are chaotic and one must rely on geological data to infer climate conditions. We conclude that moderately high obliquity and wide obliquity variations were probable during the last 40,160 Myr. We tentatively conclude that high obliquity peaks (>40,45°) may have occurred episodically through the last 210,430 Myr. A sharp step in the frequency distribution of wall steepness at 20° may indicate a geologically long period prior to that time where obliquity never exceeded 40,45°. [source] Workshop summary on physical and chemical properties of potential Earth impactorsMETEORITICS & PLANETARY SCIENCE, Issue 12 2002W. F. Huebner The goal was to develop a roadmap for determining the physical and chemical properties of NEOs in the coming decades to meet the scientific requirements for development of Earth collision avoidance technology. We identified many properties that are desired, but four measurements are needed most critically for any potentially hazardous NEO: (1) its mass, (2) its mass distribution, (3) its material strengths, and (4) its internal structure. Global (whole-body) properties, such as material strengths and internal structure, can be determined best from the analyses of permeating waves: artificially initiated seismology and multifrequency reflection and transmission radio tomography. Seismology provides the best geophysical (material strengths) data of NEOs composed of consolidated materials while radio tomography provides the best geological data (e.g., the state of fracture) of electrically nonconducting media. Thus, the two methods are complementary: seismology is most suitable for stony and metallic asteroids, while radio tomography is most appropriate for comet nuclei and carbonaceous asteroids. The three main conclusions are (1) remote sensing for physical characterization should be increased, (2) several dedicated NEO missions should be prepared for geophysical and geological investigations, and (3) that it is prudent to develop and prove the technology to make geophysical measurements on NEOs now. [source] Testing phylogeographic predictions on an active volcanic island: Brachyderes rugatus (Coleoptera: Curculionidae) on La Palma (Canary Islands)MOLECULAR ECOLOGY, Issue 2 2006BRENT C. EMERSON Abstract Volcanic islands with well-characterized geological histories can provide ideal templates for generating and testing phylogeographic predictions. Many studies have sought to utilize these to investigate patterns of colonization and speciation within groups of closely related species across a number of islands. Here we focus attention within a single volcanic island with a well-characterized geological history to develop and test phylogeographic predictions. We develop phylogeographic predictions within the island of La Palma of the Canary Islands and test these using 69 haplotypes from 570 base pairs of mitochondrial DNA cytochrome oxidase II sequence data for 138 individuals of Brachyderes rugatus rugatus, a local endemic subspecies of curculionid beetle occurring throughout the island in the forests of Pinus canariensis. Although geological data do provide some explanatory power for the phylogeographic patterns found, our network-based analyses reveal a more complicated phylogeographic history than initial predictions generated from data on the geological history of the island. Reciprocal illumination of geological and phylogeographic history is also demonstrated with previous geological speculation gaining phylogeographic corroboration from our analyses. [source] How has a shortage of census and geological information impeded the regularization of artisanal and small-scale mining?NATURAL RESOURCES FORUM, Issue 1 2004Gavin Hilson Abstract There is growing consensus that a combination of laissez-faire policies, ad hoc regulation and debilitating support services has perpetuated socio-economic and environmental deterioration in the artisanal and small-scale mining (ASM) industry. However, a lack of anthropological and geological information on ASM prevents many governments both from improving the policy environment of the industry, and from providing more robust extension services to its operators. This article aims to examine more precisely how a deficiency of baseline census and geological data has inhibited industry formalization and undermined many of the measures implemented to address pressing problems at ASM sites. Specifically, it is argued that insufficient knowledge of artisanal mining populations , including their demographic structure , and of areas suitable for ASM activities affects the ability of a government to regularize, as well as to improve, the organization of this largely informal sector of industry. Case studies of Ghana and Zimbabwe are used to illustrate how the undertaking of low-budget projects in areas of geological prospecting and population analysis could improve the efficiency of ASM assistance. [source] On the Ghoudi, Khoudraji, and Rivest test for extreme-value dependenceTHE CANADIAN JOURNAL OF STATISTICS, Issue 4 2009Noomen Ben Ghorbal Abstract Ghoudi, Khoudraji & Rivest [The Canadian Journal of Statistics 1998;26:187,197] showed how to test whether the dependence structure of a pair of continuous random variables is characterized by an extreme-value copula. The test is based on a U -statistic whose finite- and large-sample variance are determined by the present authors. They propose estimates of this variance which they compare to the jackknife estimate of Ghoudi, Khoudraji & Rivest (1998) through simulations. They study the finite-sample and asymptotic power of the test under various alternatives. They illustrate their approach using financial and geological data. The Canadian Journal of Statistics © 2009 Statistical Society of Canada Ghoudi, Khoudraji & Rivest (1998) ont montré comment tester que la structure de dépendance d'un couple d'aléas continus est caractérisée par une copule de valeurs extrêmes. Le test s'appuie sur une U -statistique dont les auteurs déterminent ici la variance asymptotique et à taille finie. Ils proposent des estimations de cette variance qu'ils comparent à l'estimateur jackknife de Ghoudi, Khoudraji & Rivest (1998) à l'aide de simulations. Ils étudient les puissances à taille finie et asymptotique du test sous diverses contre-hypothèses. Ils illustrent leur propos avec des données financières et géologiques. La revue canadienne de statistique © 2009 Société statistique du Canada [source] The role of glacitectonic rafting and comminution in the production of subglacial tills: examples from southwest Ireland and AntarcticaBOREAS, Issue 4 2007John F. Hiemstra Sedimentological and structural geological data from two sites in southwest Ireland and Antarctica provide evidence for the formation of subglacial till by the brecciation and crushing of bedrock rafts. Up-sequence transitions, from undisturbed bedrock, to deformed bedrock, to crushed and brecciated bedrock, to massive matrix-supported till with far-travelled erratics, represent a process-form continuum of till production. Initially, bedrock fragments and rafts up to several metres in length are liberated from the substrate by glacitectonic thrusting and plucking. These rafts are then crushed to produce the matrix of a till. Such products are commonly referred to as comminution tills, although the original definition focused primarily on the second phase of the process (crushing of bedrock rafts and fragments) as well as abrasion of bedrock. Data from Ireland and Antarctica indicate that rafting of bedrock is an essential part of the process of till formation. This process is facilitated by weak sedimentary bedrock, which can be displaced along joints and bedding planes to form rafts that are then incorporated into the ,proto-till' prior to being crushed subglacially. Our field data suggest that bedrock failure and displacement of such rafts can occur to depths of 3 m. The occurrence of erratics in the uppermost part of the till demonstrates that the glacier effectively mixes far-travelled and local materials. [source] Late Quaternary development of the southern sector of the Greenland Ice Sheet, with particular reference to the Qassimiut lobeBOREAS, Issue 4 2004ANKER WEIDICK The evolution of the southern Greenland Ice Sheet is interpreted from a synthesis of geological data and palaeoclimatic information provided by the ice-sheet cores. At the Last Glacial Maximum the ice margin would have been at the shelf break and the ice sheet was fringed by shelf ice. Virtually all of the present ice-free land was glaciated. The initial ice retreat was controlled by eustatic sea level rise and was mainly by calving. When temperatures increased, melt ablation led to further ice-margin retreat and areas at the outer coast and mountain tops were deglaciated. Retreat was interrupted by a readvance during the Neria stade that may correlate with the Younger Dryas cooling. The abrupt temperature rise at the Younger Dryas,Holocene transition led to a fast retreat of the ice margin, and after ,9 ka BP the ice sheet was smaller than at present. Expansion of the ice cover began in the Late Holocene, with a maximum generally during the Little Ice Age. The greatest changes in ice cover occurred in lowland areas, i.e. in the region of the Qassimiut lobe. The date of the historical maximum advance shows considerable spatial variability and varies between AD 1600 and the present. Local anomalous readvances are seen at possibly 7,8 ka and at c. 2 ka BP. A marked relative sea level rise is seen in the Late Holocene; this is believed to reflect a direct glacio-isostatic response to increasing ice load. [source] Holocene vegetation and climate changes in Hoton-Nur basin, northwest MongoliaBOREAS, Issue 2 2000PAVEL TARASOV Radiocarbon-dated pollen and diatom records from Hoton-Nur lake (48°40'N, 88°18'E), northwest Mongolia are used to reconstruct Holocene vegetation and climate changes. Steppe, which covered the area some time before 9000 BP (all ages are given in 14C BP), was replaced by boreal conifer forest-steppe by 9000,8500 BP. At the same time, planktonic diatoms increased in abundance from 5 to 45%. After 4000 BP there was a sharp reduction in forest and re-establishment of steppe. Changes in the pollen composition were accompanied by a decrease in the abundance of planktonic diatoms from 35,50% (between 9000 and 5500 BP) to less than 10% soon after 4000 BP. These and other published data from Mongolia suggest wetter conditions during the early and middle Holocene than those of today. This pattern probably reflects an expansion of the Pacific monsoon recorded in geological data from China and simulated in climate-model experiments, and suggests that the summer monsoon influenced a larger area than might appear if the Chinese records only are taken into consideration. [source] Collision Tectonics between the Tarim Block (Basin) and the Northwestern Tibet Plateau: New Observations from a Multidisciplinary Geoscientific Investigation in the Western Kunlun MountainsACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 2 2001XIAO Xuchang Abstract New results from deep seismic reflection profiling, wide-angle reflection-refraction profiling and broadband seismic experiments reveal that a series of south-dipping reflectors occur on the southern margin of the Tarim block (basin). However, it is these south-dipping structures that are intercepted by another series of north-dipping reflectors at depths from 30 to about 150 km beneath the foreland of the W Kunlun Mountains. No evidence from the above geophysical data as well as geochemical and surface geological data indicate the southward subduction of the Tarim block beneath the W Kunlun Mountains (NW Tibet plateau), forming the so-called "two-sided subduction" model for the Tibet plateau as proposed by previous studies. So the authors infer that the tectonic interaction between the Tarim block and the W Kunlun block was chiefly affected by a "horizontal compression in opposite directions", which brought about "face-to-face contact" between these two lithospheric blocks and led to the thickening, shortening and densifying of the lithosphere. Hence a "delamination" was formed due to the gravitational instability created by the thickening and densifying; then alkaline basic volcanic rocks (mainly shoshonite series) was erupted along the northern margin of the Tibet plateau owing to the delamination. This inference for the formation of the alkaline basic volcanics has been confirmed by recent geochemical and petrological studies in Tibet, indicating that different contacts control different magmatic activities: the alkali basalts are always developed in the "horizontal shortening boundary (contact)" on the northern margin of the Tibet plateau, while the muscovite granite and two-mica granite (leucogranite) in the "subductional contact" on the southern margin of the Tibet plateau. [source] Earliest Miocene hominoid from Southeast AsiaAMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 2 2004Yutaka Kunimatsu Abstract A new hominoid fossil site, Chiang Muan in northern Thailand, yielded the first finding of a large-bodied Miocene hominoid in Southeast Asia. This specimen (CMu6-1,00) was preliminarily reported by Kunimatsu et al. ([2000a] Primate Res. 16:299). Later, Chaimanee et al. ([ 2003] Nature 422:61,65) reported additional hominoid teeth from the same site, but all of them were collected from younger deposits (the Upper Lignite Member, in Nagaoka and Suganuma [ 2002] Primate Res 18:159,164). The specimen described here (CMu6-1,00) was recovered from the Lower Lignite Member (Nagaoka and Suganuma [ 2002] Primate Res 18:159,164), which is probably several hundred thousand years older than the Upper Lignite Member (Suganuma et al. [ 2002] Primate Res. 18:165,173). This article provides a detailed description of this hominoid specimen and paleontological/geological data of the fossil site at Chiang Muan. The hominoid specimen (CMu6-1,00) is an isolated upper molar (right M1 or M2), similar in size to modern orangutans (Pongo pygmaeus). This upper molar has low and voluminous cusps, relatively thick enamel, and relatively low relief of the dentine/enamel junction, with only a faint remnant of the lingual cingulum. The age of Chiang Muan is estimated to be the latest Middle Miocene (ca. 11,12 Ma), based on the mammalian fossils (Nakaya et al. [ 2002] Primate Res. 18:131,141) and paleomagnetic study (Suganuma et al. [ 2002] Primate Res. 18:165,173). This suggests that the Chiang Muan Hominoid in the present study is an earlier member of Eastern Eurasian Miocene hominoids. Am J Phys Anthropol, 2003. © 2003 Wiley-Liss, Inc. [source] | ||||||||||||||||