bluuebunny/crossref_metadata_2025_split huggingface dataset:
Geomagnetic reversal history
Authors: Lowrie William 
Published: July 2007

ABSTRACTThe history of geomagnetic polarity reversals in the Cenozoic and Late Mesozoic is well known since the Late Jurassic (Oxfordian). A continuous record of polarity has been derived for this time interval from the interpretation of oceanic magnetic anomalies. Most of the polarity chrons in this oceanic record have been verified and dated in coordinated magnetostratigraphic and biostratigraphic studies. This has led to the generation of progressively refined and improved geomagnetic reversal time‐scales that provide a framework for absolute dating of palaeontological zonations. By serving as a basis for statistical analysis of reversal frequency they provide information relevant to processes in the Earth's core. The rate of reversals since the Late Cretaceous shows a steady increase on which a cyclical variation appears to be superposed. A stochastic model for reversals predicts a Poisson distribution of polarity interval lengths. The polarity time scales contain many fewer short (± 50 kyr) polarity chrons than a Poisson distribution, and it has been suggested that a gamma renewal process with index greater than unity is a more appropriate statistical model. The statistical arguments give no convincing reason for abandoning the model and other, physical reasons must be sought to explain the incompleteness of the reversal record. The discovery and verification of short chrons in the oceanic record may best be investigated by deep‐tow magnetometer surveys. The reversal history before the Late Jurassic is not well known. Magnetostratigraphy in coeval Early Jurassic sections has not given correlatable records and it has not been possible to compile a definitive polarity sequence. Evaluation of geomagnetic polarity history for the Early Mesozoic and the Palaeozoic will require unambiguous magnetostratigraphy in well‐dated sections where verification of the polarity pattern is possible at the fossil zone or stage level.
No water, no plate tectonics: convective heat transfer and the planetary surfaces of Venus and Earth
Authors: Mian Z.U. , Tozer D.C. 
Published: July 2007

ABSTRACTWe consider the influence of water on the near‐surface rheology of Venusian and terrestrial rocks and hence the way their heat transfer processes have been able to shape their planetary surfaces. We suggest that Earth is now unique in having plate‐like surface movements at velocities characteristic of ‘deep’ material in self‐regulating convective states (∼ few cm/year) only because liquid water is there available to facilitate mechanical failure of its lithosphere (sic). The relative absence of free water on Venus is thought to more than compensate for the effect of higher temperatures on the deformability of its surface rocks and is interpreted as the reason for an absence of Earth‐like platetectonics and the distinctive distributions of volcanism and seismicity accompanying such a process for > 109 years. The characteristics of Venusian volcanism in its post plate‐tectonic era are now expected to be similar to Earth's intraplate (‘hotspot’) volcanism.
The fossil vertebrates from Lano (Basque Country, Spain); new evidence on the composition and affinities of the Late Cretaceous continental faunas of Europe
Authors: Astibia H. , Buffetaut E. , Buscalioni A.D. , Cappetta H. , Corral C. , Estes R. , Garcia‐Garmilla F. , Jaeger J.J. , Jimenez‐Fuentes E. , Loeuff J. Le , Mazin J.M. , Orue‐Etxebarria X. , Pereda‐Suberbiola J. , Powell J.E. , Rage J.C. , Rodriguez‐Lazaro J. , Sanz J.L. , Tong H. 
Published: July 2007

ABSTRACTA newly discovered fossil locality at Lano (Basque Country) has yielded a vertebrate assemblage of probably Maastrichtian age comprising fishes, amphibians, reptiles and mammals. It considerably enlarges our knowledge of the Late Cretaceous continental faunas of Europe, hitherto based on a much less complete record. Some taxa are recorded for the first time in Europe, and the fauna also contains the oldest known representatives of some groups (amphisbaenians, salamandrids). The Lan assemblage reveals an original fauna comprising both forms related to Asian and North American groups and elements with Gondwanan affinities.
A comparison of surface fitting algorithms for geophysical data
Authors: El Abbass T. , Jallouli C. , Albouy Y. , Diament M. 
Published: July 2007

ABSTRACTMany treatments in geophysics require regular grids of data. Since the data are generally recorded irregularly (e.g. gravity measurements along roads) or even on tracks (e.g. satellite measurements), it is necessary to grid the observed data.We present the result of a comparison of various surface fitting algorithms carried out in order to check their reliability. Two different types of sampling have been verified: (i) clouds of points and (ii) points along tracks. Five algorithms have been extensively tested: (1) polynomial fit, (2) algorithm using a combination of spline‐laplace, (3) krigeage (4) least‐squares fitting method, and (5) finite element method. The suitability of each method for different sets of data and the limitations (in terms of amplitude and gradient) are discussed.
Effect of sample pretreatment and size fraction on the δ18O and δ13C values of foraminifera in Arabian Sea sediments
Authors: Sarkar A. , Ramesh R. , Bhattacharya S.K. 
Published: July 2007

ABSTRACTStable oxygen and carbon isotope ratios (δ18O and δ13C, respectively) of a planktonic foraminiferal species (Globigerinoides sacculifer) and marble carbonate were measured with and without a variety of pretreatments like ultrasonication, soaking in H2O2, methanol and roasting under vacuum. Additionally, organic matter ‐ carbonate mixtures were also analysed with and without the above pretreatments. No significant difference was found in the isotope ratios of treated and untreated samples. It appears that most of the pretreatments may not be necessary when dealing with planktonic foraminifera, especially G. sacculifer. Analysis of two different size fractions (> 400 μm and 250–400 μm) of this species reveals that the smaller size fraction is enriched in 18O and depleted in 13C relative to the bigger size fraction. It is therefore necessary to choose a proper size fraction for isotopic analyses.
Tomographic images of the upper mantle below central Europe and the Mediterranean
Authors: Spakman Wim 
Published: July 2007

ABSTRACTResults from delay time tomography of the European‐Mediterranean upper mantle are discussed and where possible interpreted in terms of geodynamic processes. Slab‐like positive velocity anomalies of which the locations correlate well with deeper seismicity are found beneath Spain, the Tyrrhenian basin, and the Aegean. These structures are interpreted as images of subducted slabs. Large aseismic regions with positive velocity anomalies are found beneath the Western Mediterranean, Italy, the Alps, Dinarides, the Pannonian basin, northern Greece, and the Aegean. These anomalies can also be linked to subducted lithosphere. From the anomaly patterns it is deduced that subduction occurred below the Western Mediterranean and along both sides of the Adriatic micro‐plate. Beneath the Dinarides and northern Greece the velocity structures suggest detachment of the slab from the surface.
Eastern Mediterranean gravity potential and the Hellenic subduction process
Authors: Remkes M.J.N. 
Published: July 2007

ABSTRACTTornographic images of the Mediterranean upper mantle P‐wave velocity structure have been used to analyse the gravity potential in the vicinity of the Hellenic subduction zone. The velocity anomalies are assumed to be proportional to density variations according to Birch's law. The effect of the topography on the geoid in the region is also calculated. The results indicate that the upper mantle geoid signal probably has significant amplitudes of several metres, but it correlates poorly with the observed geoid. The geoid calculated from topography correlates well, but has an amplitude that is too large in comparison with the observed geoid. The results show that an improved understanding of the Hellenic subduction zone geoid requires refinement of the Moho topography, so that the effect of this topography can be separated from the upper mantle signature.
Propagation anomalies in Northwestern Italy by inversion of teleseismic residuals
Authors: Cattaneo M. , Eva C. 
Published: July 2007

ABSTRACTTravel‐time residuals of teleseismic P waves were analysed in order to elucidate the crust–upper mantle structure in Northwestern Italy, and the Western Alpine Arc. Using digital data obtained from both fixed seismograph networks operating in NW Italy (notably Liguria–Piedmont) and temporary arrays with the aid of cross‐correlation techniques reliable travel‐time residuals were calculated which were then inverted to obtain models of propagation anomalies. The reliability of the inversion procedure was tested using synthetic data. The model thus obtained appears to be stable and shows strong lateral heterogeneities at a litho–asthenospheric level; in particular, it confirms the high velocity contrast caused by the ‘Ivrea Body’ in the shallower layers and the presence of Alpine ‘roots’ reaching down to at least 200 km. A statistical analysis performed on the propagation times of rays crossing the resulting four‐layered model reveals rms below 0.1 s.
The thermal structure of the Mediterranean upper mantle: a forward modelling approach
Authors: de Jonge M.R. , Wortel M.J.R. 
Published: July 2007

ABSTRACTWe develop and present an approach for gaining insight into the thermal structure of the upper mantle in a tectonically active region. As a starting point for the analysis we use regional geological reconstructions, based on data from surface geology, shallow seismics and paleomagnetism. For these reconstructions we determine the necessarily associated upper mantle processes, such as subduction. We then forwardly model the thermal structure of upper mantle corresponding with the geological reconstruction used. In this way we obtain an estimate of a very important characteristic – the temperature distribution of the upper mantle–that is independent from those estimates from the usual deep seismic methods. If sufficient detailed information on the seismological structure of the region is available, a quantitative test of our modelling results is possible, via the temperature dependence of seismic velocities. We apply our approach to the Mediterranean area, for which we will test the reconstruction published by Dercourt et al. (1986).
Laboratory seismic measurements: an aid in the interpretation of seismic field data
Authors: Kern Hartmut 
Published: July 2007

ABSTRACTThis contribution reports data and evidence from laboratory measurements of compressional and shear‐wave velocities and mineralogical, microstructural and chemical analyses in crustal rocks that may provide an aid to understanding and interpreting geophysical data. It is shown that the correlation of laboratory seismic data with stratigraphic field data can provide the necessary data base for constructing a seismic model of the Earth's crust in a particular geological area.
The role of remanent magnetization in the Southern Italian crust from aeromagnetic anomalies
Authors: Fedi M. , Florio G. , Rapolla A. 
Published: July 2007

ABSTRACTInduced magnetization in the intermediate to deep crust is insufficient to justify regional magnetic anomalies. This is an unresolved problem, that cannot be completely explained by induced and viscous magnetization. In this context, the contribution of remanent magnetization in the Southern Italian Region has been investigated from a study of long‐wavelength magnetic anomalies. By means of a shape analysis, several anomalies were found which indicate a total magnetization vector direction different from the induced one. From the good correspondence between these deduced declinations with palaeomagnetic and palaeotectonic data, we infer a remarkable manifestation of remanent magnetization in the intermediate‐crust.
The deep structure of the central Alps inferred from both geophysical and geological data
Authors: Laubscher H. 
Published: July 2007

ABSTRACTGravity surveys of the past century established that mountains have roots, seismic refraction lines shot in the second half of this century confirmed the downbulge of the Moho under the Alps, and recent reflection traverses provided new details on the behaviour of crustal layers in the deep part of the Alps. However, geophysical data are ambiguous geologically. For models of the root in terms of rock distribution to be tectonophysically acceptable, they must be the retrodeformable result of kinematic sequence that fits the geological surface data. For a cross‐section through the Swiss Alps based on refraction data and somewhat modified by the recent reflection traverses, a kinematic model compatible with large‐scale geological data may be obtained by the superposition of three Neogene phases with alternating vergence. Although Alpine collision is largely dextrally compressive in the central Alps, the N‐S component may be discussed in a cross‐section. Particularly puzzling geophysical features include a high‐velocity body in the middle crust and the disappearance of the layered foreland crust in the root. In order to account for these phenomena, it is proposed that the crustal root is interpreted as the result of complex reshuffling of middle and lower crustal masses as well as large‐scale phase transformations. The mid‐crustal highvelocity body is interpreted as a delaminated section of the lower crust of the Adria plate that was wedged into the middle crust of the Alps in the middle Miocene. The disappearance of the foreland lower crust is attributed to eclogitization attendant on the subduction of continental crust. Material balance estimates suggest that during Alpine collision large volumes of continental crust have disappeared through subduction.
Eocene simple shear and plio‐quaternary pure‐shear folding in the Central‐Eastern Algerian Atlas
Authors: Ferrari Luca , Tibaldi Alessandro , Brizzolara Livio , Maffioli Alessandro 
Published: July 2007

ABSTRACTTertiary folds of the central and eastern part of the Algerian Atlas were studied in order to assess their kinematics and regimes of deformation. Folds developed following two main phases of deformation during the Eocene and the Pliocene. The NE‐SW trending Eocene folds show a clockwise rotation of fold axis with depth, noncylindrical geometry and a right‐stepping en echelon configuration. Early secondary structures inside each fold are also rotated clockwise with respect to the younger folds. These data are in agreement with progressive ‘simple shear’ deformation. Pliocene folds strike E‐W and display a cylindrical geometry. Associated Plio‐Quaternary brittle structures show no rotational path. These observations are compatible with ‘pure shear’ style of deformation. These results, in combination with focal mechanism solutions, have important implications for the understanding of the kinematic evolution of the western segment of the African‐European plate boundary. For Algeria they imply that transcurrent motion during the Paleogene was followed by coaxial shortening with a NNW direction during Neogene‐Quaternary times. Comparison with published data for Morocco and Tunisia suggests that this transcurrent regime developed from west to east continuing from the Middle Jurassic through to the Miocene.
The Colchester forgeries: faking photographic evidence of earthquake damage
Authors: Musson R.M.W. 
Published: July 2007

ABSTRACTThe photographic archive of the 22 April 1884 Colchester earthquake, the most damaging British earthquake in the last 400 years, is wellknown. Evidence has come to light that at least two of these photographs are partly or wholly faked. This shows that not even the camera can necessarily be relied upon to accurately portray the extent of damage from historical earthquakes.
New 3–D investigative techniques for understanding the earth's interior
Authors: Bellani A. , Blasi P. , Burlini L. , Chignola E. , Fäh D. , Fedi M. , Ferrari L. , Florio G. , Giavelli A. , Lupini L. , Schreider S. Yu. , Tibaldi A. , Tramontana L. , Vaccari F. , Zappone A. 
Published: July 2007

ABSTRACTThe 3–D model of the Earth, as obtained with a brand new investigative technique, is discussed. However an international collaborative project, involving researchers from the whole world, has uncovered a severe systematic error in the new data acquisition system making the results of this new model highly questionable.
Carbon isotopes, time boundaries and evolution
Authors: Magaritz Mordeckai 
Published: July 2007

ABSTRACTThe carbon isotope composition of carbonate rocks in time‐boundary zones is interpreted as a reflection of the variations in the total biomass at mass extinction events. Better stratigraphic control and identification of hiatuses can be gained by stable isotope stratigraphic methods than with any other type of stratigraphy. It is suggested that the use of carbon isotopes can help in solving some of the problems confronting palaeontologists and lead to a better understanding of the evolutionary significance of these events.
Tholeiitic and alkalic basalts of the oldest Pacific Ocean crust
Authors: Floyd P.A. , Castillo P.R. , Pringle M. 
Published: July 2007

ABSTRACTApproximately 160 Ma old basaltic lavas obtained from ODP Site 801 in the Pigafetta Basin represent the first Jurassic oceanic crust recovered in the Pacific Ocean and the oldest in situ oceanic crust discovered anywhere. The basement consists of an upper alkali olivine basalt sequence and a lower tholeiitic sequence separated by a yellow Fe‐rich hydrothermal sedimentary deposit. The aphyric and sparsely plagiodase‐olivine±spinel phyric tholeiites exhibit depleted, open–system fractionated characteristics with trace element abundances and Pb–Nd isotopic compositions similar to normal mid‐ocean ridge basalts (N‐MORB). The aphyric alkali basalts, although showing some overlap in isotopic composition with MORB, exhibit strong similarities in terms of incompatible element abundances to ocean island basalts (OIB). They could represent either OIB‐type off‐axis volcanism or an alkalic event possibly associated with the waning stages of spreading axis volcanism in the Pigafetta Basin. All lavas have undergone low‐grade anoxic smectite–carbonate alteration, although flows underlying the Fe‐rich sediments have suffered hydrothermal alteration and fracturing.
Subduction and eduction of continental crust: major mechanisms during continent‐continent collision and orogenic extensional collapse, a model based on the south Norwegian Caledonides
Authors: Andersen Torgeir B. , Jamtveit Bjørn , Dewey John F. , Swensson Eivind 
Published: July 2007

ABSTRACTDuring continental collision in the middle Silurian, the thickness of the lithosphere under the Caledonides of S. Norway was doubled by subduction of the western margin of Baltica, including the Western Gneiss Region, under Laurentia. Crustal rocks of the Baltic plate reached sub‐Moho depths of near 100 km or more as inferred from the presence of coesite in eclogites. Isostatic calculations indicate an average elevation of the mountain chain of about 3 km at this stage. The subducted lithosphere experienced vertical constrictional strains as a result of slab‐pull by its heavy and cold root. Eduction of the deeply buried crustal material was initiated by decoupling of the Thermal Boundary Layer in the subducted lithosphere. Isostatic rebound resulted in very rapid uplift (1–2 mm yr‐1), and the deep crust was exhumed, mainly by tectonic extensional stripping over a period of 30–40 Myr. The eduction was probably related to a rolling hinge, footwall uplift mechanism, and the early high‐pressure coaxial fabrics were overprinted by extensional simple shear as the deep crust reached middle and upper crustal levels. The model explains the present‐day normal crustal thickness under the exhumed deep rocks without necessarily invoking large‐scale lateral flow of material in the lower crust or igneous underplating.
NAA analysis of gold in minerals from Upper Cretaceous massive copper deposits in Bulgaria
Authors: Todorov Todor 
Published: July 2007

ABSTRACTMinerals from deposits Chelopech, Elshitsa, Radka and Krasen have been studied and their gold contents determined by neutron‐activation. In all deposits sulphide and sulphosalt minerals show a well‐expressed ability to concentrate gold, although their role in individual deposits is not equal. The highest concentration of gold is in bornite, tennantite, enargite and the early generations of pyrite, chalcopyrite, galena and sphalerite. The low content of gold in the late generations of pyrite, chalcopyrite, galena and sphalerite is due to the process of recrystallization and redeposition. The data obtained show that gold has been extracted entirely from the solutions of the early quartz‐pyrite stage mineralizations while during the later quartz‐sulphosalt‐sulphide and quartz‐carbonite‐sulphate stages it was only re‐deposited and concentrated.
Postglacial land uplift patterns of south Sweden and the Baltic Sea region
Authors: Svensson Nils‐Olof 
Published: July 2007

ABSTRACTComparison of the land uplift pattern for the last 10,300 years, shown by studies of raised shorelines of the Baltic Ice Lake, with the pattern of present‐day land uplift of Fennoscandia, shows that significant regional changes of uplift pattern have taken place. Some of these changes seem to be related to a halt in ice retreat during the Younger Dryas cold stage. It is also probable that some observed anomalies in the present uplift are not of glacio‐isostatic origin, but are possibly related to structures in the lower lithosphere and upper mantle or large scale tectonics.
Gravity change, geoid change and remaining postglacial uplift of Fennoscandia
Authors: Ekman Martin 
Published: July 2007

ABSTRACTThe result obtained hitherto on the Fennoscandian land uplift gravity line indicates that the postglacial uplift process might be more complicated than a pure horizontal flow of mantle (‘Bouguer model’). Simple formulae, valid for a more arbitrary model, are developed for the change of the geoid and for the remaining land uplift. Numerical applications yield a geoid change of about 0.4 mm yr‐1 and a remaining land uplift of the order of 50 m, but the latter quantity is very difficult to determine with reasonable accuracy.
Course and origin of the Fennoscandian uplift: the case for two separate mechanisms
Authors: Mörner Nils‐Axel 
Published: July 2007

ABSTRACTThe classical glacial isostatic uplift paradigm of Fennoscandia is in need of a thorough revision as to its course and origin. The total uplift amounts to 830 m (not 300 m). The centre of uplift started to rise 13,000 BP (not 9300 BP). The uplift appears to be composed of two separate mechanisms; one true glacial isostatic rebound, and one linear uplift factor possibly representing a phase boundary adjustment. Calculations and modelling must treat these two factors independently (which has not been the case).
Human activities and environmental stress: some essentials revisited1
Authors: Schidlowski Manfred 
Published: July 2007

ABSTRACTCurrent pollution of the total environment is caused by waste products of the extrasomatic metabolism of Homo sapiens who, since the beginnings of the industrial revolution, has raised his energy consumption by a factor of 10–20 above the basic metabolic rate of the single individual. While the increased energy flow through the human ecosystem has brought about an improvement of the human condition unprecedented in the history of mankind (including a doubling of the average life expectancy), it is beset also with an intrinsic maladaptive potential for the possible emergence of an autotoxic effect. The future of high‐energy (industrial) societies will, accordingly depend on man's capability to maintain an adequate energy flow while hopefully minimizing the potential impact of autotoxicity on his environment by suitable technological fixes.