bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evidence for bacterial degradation of hydrocarbons in uranium deposits
Authors: Landais Patrick 
Published: July 2007

ABSTRACTThe biodegradation of free hydrocarbons migrated in reservoir faaes has often been observed in petroleum exploration. This bacterial alteration is characterized by the progressive removal of different classes of hydrocarbons. One of the most important consequences of biodegradation is the reduction of sulphate, as noted in several Pb‐Zn deposits. Biodegradation of oils spatially associated with uranium deposits has also been observed in Lodeve (France), Grand Canyon (Arizona, USA), Temple Mountain (Utah, USA) and leads to the transformation of fluid oils into solid bitumens. Within this study emphasis has been laid on the relationships between the effects of biodegradation on organic matter (oxidation or aromatization) and the nature of aqueous solutions analysed in fluid inclusions trapped in authigenic minerals. Different mechanisms are proposed to explain the transformations of organic matter during biodegradation and their possible links with ore‐forming processes.
One‐dimensional modelling of episodic fracturing: a sensitivity study
Authors: Cao S. , Lerche I. , Lyon W. G. 
Published: July 2007

ABSTRACTEpisodic fracturing is discussed in relation to both sedimentary deposition rates and lithology, as well as to pressure release criteria and vertical numerical grid sizes of a one‐dimensional fluid‐flow/ compaction model. It is shown that the evolution of episodic fracturing is a ruggedly stable pattern for fine‐scale gridding, and that a critical fracture pressure of around 0.8 of the lithologic overburden is suggested.
Low‐angle faults above and below a blueschist belt—Tinos Island, Cyclades, Greece
Authors: Avigad Dov , Garfunkel Zvi 
Published: July 2007

ABSTRACTNew observations from the Island of Tinos, Greece, allow a better definition of the structural position of the Alpine (Eocene) blueschist belt exposed in the islands of the Aegean Sea. These blueschists, over a significant part of the Aegean sea, are delimited from below by a low‐angle thrust fault, while from above they are delimited by a low‐angle, normal‐type fault which omits a substantial crustal interval. Both underlying and overlying rocks were not affected by the high? metamorphism. The rapid uplift and exhumation of the high? rocks was therefore mainly the result of fault movements rather than erosion and whole‐crust uplifting. The low‐angle normal fault apparently had a major role in the uplift of the blueschists.
Vanadiferous minerals from the Nereus Deep, Red Sea
Authors: Jedwab Jacques , Blanc Gérard , Boulegue Jacques 
Published: July 2007

ABSTRACTThe chemical analysis by EMPEDS of 140 samples in cores from six Red Sea troughs and basins has led to the discovery in the Nereus Deep of high vanadium concentrations (up to 1.3% V2O3) in several bulk samples, and to the isolation of a major magnetite phase. This vanado‐magnetite, remarkable for its high content of vanadium (mean = 1.45% V2O3) and its lack of titanium, is frequently zoned, the V‐content decreasing toward the outer zones. Oxides with up to 42% V2O3, have also been found. Since the origin of the magnetite is clearly authigenic, its high vanadium and low titanium concentrations are traced back to the differential hydrothermal leaching of Fe—Ti‐oxides which occur profusely in basic eruptive rock clasts, actually present in some of the overlying seams.
Fluidization pipes in volcaniclastic mass flows, Volcan Hudson, Southern Chile
Authors: Best James L. 
Published: July 2007

ABSTRACTThe presence of fluidization pipes within pyroclastic sediments has been proposed as a criterion for differentiating these volcaniclastic deposits from those of epiclastic mass flows. Observations of pipe structures within low‐temperature epiclastic mudflows produced by the 1971 eruption of Volcan Hudson, Southern Chile, demonstrate that this assumption is invalid and that the presence of pipes may only be utilized to interpret the precise mechanics of the fluidization process itself.
In vitro growth of iron sulphide chimneys: possible culture chambers for origin‐of‐life experiments
Authors: Russell Michael J. , Hall Allan J. , Turner Dugald 
Published: July 2007

ABSTRACTIron monosulphide globules and tubes grown in the laboratory have similar morphologies to the fossil pyrite botryoids and chimneys found in the Silvermines exhalative sedimentary ore‐body of Carboniferous age in Ireland. We envisage analogous fine structures growing at hot springs (100–200°C) in the earliest oceans as having provided the culture chambers and flow reactors for life to originate by phosphorylation and growth of organic molecules on the iron sulphide surfaces. Such sulphide structures grown in the laboratory could be used in origin‐of‐life experiments.
Organic sulphur fixation in freshwater lake sediments and the implication for US ratios
Authors: Losher A.J. , Kelts K.R. 
Published: July 2007

ABSTRACTA comparative analysis of two sediment cores from perialpine lakes (L. Zürich and L. Geneva) helped to clarify pathways of sulphur fixation in freshwater sediments. Despite greater than three‐fold differences in lake water sulphate concentration equal amounts of sulphur are fixed in the sediments. The maximum sedimentary sulphur concentrations attain 1% (dry weight) which is similar to the sulphur content of modem, near‐shore marine sediments. This is also expressed in low Corg/Stot ratios which range from 2.5–8.An analysis of the sulphur pools showed that organic sulphur compounds are the main components of the sedimentary sulphur, accounting for ˜ 80% and ˜ 60% of the total sulphur in Lakes Zürich and Geneva, respectively. The largest single sulphur pool is the sulphate‐esters, which comprise 40–60% of the total sedimentary sulphur. Substantial amounts of the organic sulphur compounds must be formed within the sediment by boundary‐layer microbial communities at the oxic‐anoxic transition zone. This possibly suggests rapid recycling of sulphur in suboxic zones. Because of low concentration of SO24‐‐ in the watermass, the zone of sulphate reduction is very thin. This coupled with the mobility of some sulphide oxidizing microbial colonies (e.g. Beggiutoa) potentially results in an almost complete recycling of the sulphur pool near the sediment‐water interface. Reduced sulphur caught in this cycling process is unavailable for sedimentary pyrite formation. The Corg/Spyriteratios for these sediments are thus high. If organically bound sulphur is not completely transformed into pyrite during late diagenesis, the Corg/ Spyrite ratio can serve as a sensitive indicator for the salinities of anaent depositional environments.
Low‐latitude anhydrite from the Red Sea coast: palaeoclimaticand palaeohydrological implications
Authors: Gunatilaka A. 
Published: July 2007

ABSTRACTRecent supratidal anhydrite (CaS04) is reportedly confined to a latitudinal range of ˜ 24–30°N. Because of this apparent constraint, it is problematical to relate known distributions of ancient deposits to palaeomagnetically determined latitudes. Recent work on the Red Sea coast of the Sudan shows that anhydrite is present south of 18°N and possibly down to 15°N latitude. In Arabia and North America ancient sabkha anhydrites occupy near‐equatorial positions, which imply climatic belts within subtropical high‐pressure cells. There is no reason why anhydrite should not occur at lower latitudes, provided the depositional area is within an effective rain‐shadow where evaporation far exceeds rainfall (as in the Red Sea region).
Three recent larger earthquakes offshore Norway
Authors: Hansen Roger A. , Bungum Hilmar , Alsaker Alfred 
Published: July 2007

ABSTRACTThree earthquakes of magnitude around 5 occurred offshore western Norway on 5th February, 1986, on 8th August, 1988, and on 23rd January, 1989. These earthquakes, representing the highest seismic activity level in this area for at least 30 years, were all felt by people over most of southern and central Norway. Focal‐mechanism solutions for these earthquakes indicate thrust faulting along N‐S to NNE‐SSW striking fault planes, in response to NW‐SE compressional stress, most probably of plate tectonic origin.A number of high‐quality digital recordings of the ground motions at various distances from these and other recent earthquakes in Norway have shown that source spectral as well as wave attenuation characteristics in this area are reasonably consistent with what has been derived from other intraplate areas.
Geological events in the bible
Authors: Bentor Y.K. 
Published: July 2007

ABSTRACTThe books of the bible contain numerous, frequently very exact, descriptions of geological events. Some of these are discussed here: earthquakes and their accompanying landslides (the crossing of the River Jordan), seiches and tsunamis (the flood), flooding (Sodom and Gomorrah), faulting, burning gas seepages (the Burning Bush) and volcanism (Mount Sinai). These geological events appear in the biblical text mainly for artistic reasons; they serve as a suitable background to dramatize the biblical account; they create a supernatural atmosphere for the main stories, but the time and place at which they occurred are of no importance to the narrator and might be shifted freely.
On the origin of copper mineralization in the Kupferschiefer: a suIphur isotope study*
Authors: Sawlowicz Zbigniew 
Published: July 2007

ABSTRACTSulphur isotopic compositions of copper and iron sulphides (dispersed and vein mineralization) from the Polish part of the Kupferschiefer were determined and compared with data from the literature. Most of the δ34S values of sulphides range from about ‐40 to ‐25%, indicating sulphide precipitation during bacterial sulphate reduction in an open system which gradually chanes into a closed system. Sulphides from veins are usually enriched in 34S compared to finely dispersed mineralization and were probably formed in a more closed system. Copper sulphides are generally a few permil heavier than pyrite. Coupled with detailed microscopical observations the isotope data suggest that the mineralization is either syngenetic or early diagenetic.
Late Cretaceous evolution of the Judean Mountains as indicated by ostracodes
Authors: Flexer A. , Gilat A. , Hirsch F. , Honigstein A. , Rosenfeld A. , Rueffer T. 
Published: July 2007

ABSTRACTThe Judean Mountains’ anticlinorium, Israel, a part of the Syrian Arc fold system, underwent several phases of compressional folding, uplift and faulting in post‐Turonian through Quaternary times. This study emphasizes the earliest tectonic phase of earIy Late Coniacian age. Ostracode biozonation clearly indicates the duration and extension of Senonian sedimentation and timing of onlap over the evolving Judean Mountains’ structure.
Microdistribution of boron: particle‐track images from samples of a Caledonian igneous complex
Authors: Sauerer A. , Troll G. , Matthies D. 
Published: July 2007

ABSTRACT7Li recoil tracks in LexanR formed as a product of irradiation with thermal neutrons give an image of in sifu‐microdistribution of boron in dioritic to granitic rocks of the Caledonian Ballachulish zoned complex and in a carbonate rock from its contact aureole. The images exhibit a polyphase incorporation of boron into primary and secondary minerals. The boron microdistribution is inhomogeneous. Isomorphous incorporation of boron into pyroxene and plagioclase during the main stage of crystallization cannot be established, because the boron distribution is blurred by secondary alteration. In contrast to the intracrystalline feature, the crystal interfaces are enriched in boron. Increased concentrations are also disclosed by overgrowths of primary crystals, exsolution lamellae in alkali feldspar and alteration rims of clinopyroxene. The highest amounts of boron in a siliceous dolomite marble of the contact aureole are found in the alteration products of olivine.
Occurrence patterns of large earthquakes in the seismic zones along the Hellenic Arc
Authors: Papadimitriou E.E. 
Published: July 2007

ABSTRACTOccurrence patterns of large shallow and intermediate depth earthquakes in the seismic zones along the Hellenic Arc have been investigated. It is shown that throughout this active region the earthquakes tend to occur in a rather systematic manner. At each time‐period earthquakes occur within a discrete activated segment of the arc. These occurrence patterns are considered to offer an insight into identifying where large earthquakes are expected to occur in the future.
Periodicities of CaCO3 cycles in the Pliocene of Sicily: discrepancies with the quasi‐periods of the Earth's orbital cycles?
Authors: Hilgen F.J. , Langereis C.G. 
Published: July 2007

ABSTRACTA high‐resolution CaCO3 record in combination with a detailed magnetostratigraphy is presented for the rhythmically bedded marly sequence of the Pliocene Trubi Formation on Sicily (Italy).Magnetostratigraphic age calibration and subsequent spectral analysis of the variatrions in CaCO3 content yield a remarkably consistent discrepancy between the resulting periodicities and the corresponding quasi‐periods of the Earth's orbital cycles. This discrepancy can only be explained by assuming that ages assigned to polarity reversal boundaries in the geomagnetic polarity time‐scale lack sufficient precision.A new polarity time‐scale is presented for the major part of the Gilbert and Gauss Chron using the radiometrically dated Gilbert‐Gauss Chron boundary at 3.40 Ma as an age reference point and extrapolating an average quasi‐period of 21.7 kyr of the precession cycle as the periodicity of small‐scale colour annex CaCO3 cycles.
Milankovitch control of foraminiferal assemblages from the Cenomanian of southern England
Authors: Leary P.N. , Cottle R.A. , Ditchfield P. 
Published: July 2007

ABSTRACTA succession of foraminiferal assemblages recorded across three Cenomanian marl chalk‐marl rhythms is interpreted as a function of occasional high pelagic carbonate production induced by warmer surface waters. The changes in the benthonic assemblages are related to the introduction of increased amounts of carbonate sediment, Fluctuations in surface water temperature and associated productivity changes may be a consequence of orbital (precessional) forcing of the climate. Chalk formation is likely to have been much more rapid than marl formation.
A Milankovitch scale for Cenomanian time
Authors: Gale Andrew S. 
Published: July 2007

ABSTRACTA detailed cyclostratigraphy is present in the rhythmically bedded Cenomanian hemipelagic chalks of the northern Anglo‐Paris Basin, which can be correlated over 100,000 km2. Individual decimetre‐scale couplets probably represent the precession cycle (modes at 18 or 23 kyr), and can be readily grouped in sets averaging five, indicative of the short cycle of eccentricity (100 kyr). A composite cyclostratigraphy for the basin is presented here, and is used as the basis for a Cenomanian time‐scale (20 and 100 kyr units). The total duration of the Cenomanian thus obtained (4.4 Myr) compares well with recent radiometric dates of 4.0–4.5 Myr. The time‐scale is used to estimate the length of ammonite, inoceramid, and planktonic foraminiferal zones, the rates of formation of authigenic minerals (glauconite), sedimentation rates and the duration of transgressions and anoxic events.
Orbitally mediated cycles from the Turonian of southern England: their potential for high‐resolution stratigraphic correlation
Authors: Cottle R.A. 
Published: July 2007

ABSTRACTDetailed sampling of two sections of Turonian‐aged Chalk from southeast England for foraminifera has revealed that cyclical abundance changes in many species and genera were mediated by orbitally induced climatic cycles. These cycles can be used for high‐resolution stratigraphic correlation of the two sections and as a possible means of re‐estimating the duration of the Turonian period.
Cyclic geomagnetic changes in Mid‐Cretaceous rhythmites, Italy
Authors: Napoleone Giovanni , Ripepe Maurizio 
Published: July 2007

ABSTRACTMagnetic secular variation is recorded as a quasi‐rhythmical process of uncertain origin. Rhythmic changes recorded in the Scisti a Fucoidi in the central Apennines of Italy, pelagic sediments of Mid‐Cretaceous (Late Albian) age, show strong correspondence to patterns of orbital variation. In the same strata cyclic magnetic variations are found with peaks in the same range (105, 40, 26,19 kyr). These results appear to support earlier suggestions that secular variations may be related to these astronomical patterns.
Planktonic foraminiferal distribution record productivity cycles: evidence from the Aptian‐Albian Piobbico core (central Italy)
Authors: Silva Lsabella Premoli , Ripepe Maurizio , Tornaghi M. Emilia 
Published: July 2007

ABSTRACTThe Aptian‐Albian ‘Scisti a Fucoidi’ varicoloured pelagic sediments in central Italy, show a ‘couplet’ alternation of carbonate‐rich/carbonate‐poor layers, which are interpreted as the sedimentary expression of precession (frequency 19–23 kyr). Carbonate content, chromatic variation, and planktonic foraminiferal abundance were analysed at a 1‐cm spacing for a 10‐m interval of the Piobbico core, specifically drilled through this formation. Spectral analysis of these parameters shows a prominent signal equated to the c. 100 kyr cycle of orbital eccentricity at a sedimentation rate of 5 mm kyr−1. The coherency of the spectral response of each parameter suggests that a single mechanism controlled the whole sedimentary record. Detailed study of planktonic foraminiferal distribution of the same section at 1‐mm scale resolves the Milankovitch frequencies of 41 kyr and 18 to 23 kyr, equated with the obliquity and precessional cycles. But foraminiferal abundance is not in phase with carbonate content, which was largely controlled by calcareous nannofossils, but peaked at intermediate carbonate values. The proposed model for explaining the discrepancy at the precessional level is that foraminifera thrived at intermediate values of the precession index, when the environment was only moderately fertile but stable, while during highs of the precession index, mixing of the water column increased fertility and caused calcareous nannofossil blooms and restriction of planktonic foraminifera to few and tolerant species. The resulting bimodality of foraminiferal abundance per precessional cycle appears to be recorded in the spectrum by peaks at the 11 and 14 kyr levels. Cross correlation of foraminiferal abundances with the calcium carbonate curve over 1–2 Myr intervals produces discrepant results (apparent phase lags) which we attribute to differences in the response to the fundamental eccentricity cycles.
Rhythmic pelagic successions and terrestrial orbital variations. The example of the Lower Cretaceous from Angles (SE France)
Authors: Rio Michel , Cotillon Pierre , Ferry Serge 
Published: July 2007

ABSTRACTAn harmonic analysis of limestone bed and marl interbed thicknesses of pelagic Berriasian‐Barremian interval from the Angles area (SE France) shows that marly parts of the succession contain frequencies significantly different from calcareous ones. Some of the resulting periods are in the Milankovitch frequency band but many others are different from those predicted by the orbital theory.
Stratigraphic correlation of presumed Milankovitch cycles in the Blue Lias (Hettangian to earliest Sinemurian), England
Authors: Smith David G. 
Published: July 2007

ABSTRACTSimple digital filtering methods allow the correlation of patterns of metre‐scale cycles between outcrop sections and well logs through the Hettangian to earliest Sinemurian part of the Lower Lias in southern England. The matching of cyclic patterns is sufficiently confident to allow the identification of a significant break in the Blue Lias section at Lyme Regis (Dorset). The standard ammonite zones of the Hettangian Stage are shown to be of quantifiably unequal duration.
Astronomical frequencies for pre‐Quaternary palaeoclimate studies
Authors: Berger A. , Loutre M.F. , Dehant V. 
Published: July 2007

ABSTRACTThe sensitivity of the Earth's orbital frequencies, involved in the astronomical theory of palaeoclimates, to the Earth‐Moon distance and consequently to the length of the day and to the dynamical ellipticity of the Earth has been investigated for the last billion years. The shortening of the Earth‐Moon distance and of the length of the day back in time induces a shortening of the fundamental astronomical periods for the obliquity and the precession, a shortening which is larger for the longer periods. These periods of precession and obliquity influenced by the changing Earth‐Moon distance, length of the day and dynamical ellipticity of the Earth, have been recomputed for the last 440 million years.
Environmental Geology and the marine dimension
Authors: Hull J. H. 
Published: July 2007

ABSTRACTThis paper reviews the role of environmental geology, and the practice of environmental geology mapping, in the context of the geological, geophysical and geochemical factors which are relevant to human activity and safety.It is concluded that informed planning policies for the offshore areas are necessary. These would allow mutually acceptable and sensible exploitation of all natural resources, engineering and military developments and recreational uses, and would also take account of natural and man‐made hazards to such activities. The policies would follow from multidisciplinary, systematic, environmental studies involving international cooperation.The imperative for the earth‐science practitioner to remain sensitive to the requirements of the users of such information is recognized, as is the need to communicate unambiguously. It is concluded that geologists should look increasingly from the past to the future.
Tsunami risk in northwestern Europe: a Holocene example
Authors: Long D. , Dawson A.G , Smith D.E. 
Published: July 2007

ABSTRACTA thin, regionally extensive, laterally persistent sand layer is present within the Holocene coastal sequences of eastern Scotland, dated to 7000 yr BP. It is proposed that this deposit was caused by a tsunami wave generated by a catastrophic submarine landslide (the Second Storegga Slide) on the Norwegian continental slope. The distribution of this tsunami deposit indicates that the wave penetrated at least 2 km beyond the contemporary coastline and a minimum of 4 m above the contemporary high‐water mark. Although the frequency of tsunamis may be low in this region their effects should be considered for very long‐term or very sensitive strategic developments at coastal sites.
Glacial incisions indicating Middle and Upper PIeistocene ice limits off Britain
Authors: Wingfield R.T.R. 
Published: July 2007

ABSTRACTFrom the recognition that major incisions formed at lowland or tidewater ice sheet margins during each of the last three glacial stages, it is assumed that a standard Quaternary stratigraphy is applicable to the deposits geophysically profiled on the continental shelf off Britain. Ice limits for each glacial stadial can be mapped from the geographical distribution of the incisions.During the next glacial stage major incisions will be downcut on the present continental shelf or coastal lowlands to some 350 m below the ambient surface. This will have important environmental consequences regarding the long‐term burial of hazardous wastes.