bluuebunny/crossref_metadata_2025 huggingface dataset:
Environmental Geology and the marine dimension
Authors: Hull J. H.
Published: July 2007

This 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

A 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

From 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.
Dust deposition in the central Mediterranean (Tyrrhenian and Adriatic Seas): Relationships with marine sediments and riverine input
Authors: Correggiari A. , Guerzonid̊ S. , Lenazd̊ R. , Quarantottod̊ G. , Rampazzo G.
Published: July 2007

Major (Al, Ca, Fe, Mg, Mn, Si) and minor (Cd, Pb, Zn) elements of aeolian dust samples collected onboard ship around Italy were analysed, and the concentrations of metal in the dusts were in good agreement with previously published data from the Mediterranean Sea.

The elemental composition of dust samples collected in four subareas (Adriatic, Ionian, Tyrrhenian, and Sicily Channel) was compared with the composition of marine deep sediments obtained in the same regions: Mn, Al, Cd and Zn contents differentiated between the four areas in both sets of samples, suggesting a possible ‘geochemical signature’ of the atmospheric crustal contribution in marine deep sediments.

An estimate of the relative contribution of atmospheric dry deposition of Cd, Pb and Zn and riverine discharge indicates that: (a) the metals deposited from the atmosphere to the Adriatic basin are a small fraction (2–5%) of those discharged by the Po and Adige rivers; (b) almost the same amounts of Cd, Pb and Zn are delivered to the Tyrrhenian Sea by the atmosphere and by the Arno and Tiber Rivers.
Carbon isotopes and Precambrian—Cambrian boundary geology, South Australia: ocean basin formation, seawater chemistry and organic evolution
Authors: Tucker Maurice E.
Published: July 2007

A carbon isotope stratigraphy from the lowest Cambrian strata in the Adelaide fold belt of South Australia is interpreted in terms of the geological context of the sequence: major transgression, developing circulation patterns and upwelling resulting from an adjacent opening ocean, and biomass increases stemming from the Cambrian radiation event. There is also evidence from the textures of ooids and cements in late Precambrian‐Cambrian strata for subtle variations in seawater chemistry across the boundary and these may well have been instrumental in the development of calcareous skeletons in the early metazoans.
A geological transect from Kun Lun to Karakorum (Sinkiang, China): the western termination of the Tibetan Plateau. Preliminary note
Authors: Gaetani Maurizio , Gosso Guido , Pognante Ugo
Published: July 2007

A geological‐geophysical expedition (Ev‐K2–CNR 1988) visited the area from West Kun Lun to Karakorum (K2–Gasherbrum). Seven tectonic units including sedimentary, magmatic and metamorphic rocks were distinguished in this area; the northernmost are suggested to belong to the Kun Lun and Qiangtang Microplates. The sedimentary sequence of Shaksgam is proved to extend from the Permian to the Jurassic, with Carboniferous and Cretaceous ages more doubtful. This sequence shows intermediate affinities between the Karakorum and the Qiangtang. The two southernmost units belong to the Karakorum Microplate. The Karakorum Fault Zone comprises a complex pattern of faults and thrusts, with brittle deformation and uplifting of granitoid bodies.
Numerical basin modelling of the Sleipner field, North Sea
Authors: Wei Z.P. , Hermanrud C. , Lerche I.
Published: July 2007

Both one‐dimensional (1‐D) and two‐dimensional (2‐D) basin modelling has been carried out in the Sleipner area in the North Sea. Thermal refraction by salt and more minor convection by fluid transport combine to provide a temperature regime which is hotter at the Sleipner East field relative to the Sleipner West field by approximately 5°C at the same sub‐surface depth. These results are obtained only with 2‐D modelling, and show that such simulations are necessary to explain the spatial variations of temperature distribution at the least.

Modelling of hydrocarbon generation in the Sleipner kitchen shows that the source rocks are presently in a late gas generation state, and that a gas‐condensate is to be expected in fields draining this kitchen. Such hydrocarbon phases are encountered in the Sleipner field, confirming that the model can simulate satisfactorily hydrocarbon generation in the Sleipner area.
Persistence of quartz disequilibrium in groundwater flows
Authors: de Caritat Patrice
Published: July 2007

This paper shows how constraints can be placed on the prediction of quartz equilibration distance in subsurface water flows. This is achieved here by coupling kinetic equations for the simple (SiO2(quartz)‐H2O(water)) system to various groundwater flow parameters (compaction flow, aquifer, convection flow, and hydrothermal system). This approach determines: (1) the order of magnitude of the downstream distance necessary for equilibrium to be attained, when a flowing solution is initially out of equilibrium; and (2) the minimum flow velocity required to sustain a sufficient quartz undersaturation or oversaturation over a given distance. Geological conditions under which specific water‐rock interactions take place can be constrained with those calculations. Water flow in most subsurface environments, as idealized here, tends to equilibrate with the quartz‐rich hosting medium on a very short distance (≤ 1 m). Major exceptions are: (1) the topmost part of a compacting pile, (2) shallow and fast‐flowing aquifers, and (3) most hydrothermal systems.
The MAR‐Vema Fracture Zone intersection surveyed by deep submersible Nautile
Authors: Auzende Jean‐Marie , Bideau Daniel , Bonatti Enrico , Cannat Mathilde , Honnorez José , Lagabrielle Yves , Malavieille Jacques , Mamaloukas‐Frangoulis Vassilios , Mével Catherine
Published: July 2007

One of the two objectives of the Vemanaute cruise of the French deep submersible Nautile, was the geological study of the eastern intersection area between the Mid‐Atlantic Ridge (MAR) and the Vema Fracture Zone in the equatorial Atlantic. Fourteen dives were conducted that allowed detailed geological survey and sampling of the main morphostructural units of this area: the northern and southern walls of the fracture zone, the median ridge, the northern and southern troughs and the nodal basin. In situ observations of recent tectonic features such as furrows, ridges and circular depressions, concentrated within the southern trough, allowed us to establish the location and the size of the present‐day displacement zone. Geological investigations have shown that the nodal basin is entirely floored by basalts thus contrasting with other equivalent areas such as the Kane and Oceanographer fracture zone‐MAR eastern intersections. Finally, this study stresses the great opposition between the relatively old and tectonically inactive northern part of the fracture, and the southern part which shows active tectonics and recent volcanic activity.
The effect of Rayleigh degassing of magma on sulphur isotope composition: a quantitative evaluation
Authors: Zheng Y‐F.
Published: July 2007

The effect of Rayleigh distillation by outgassing of SO2 and H2O on the isotopic composition of sulphur remaining in silicate melts is quantitatively modelled. A threshold mole fraction of sulphur in the sulphide component of the melts is reckoned as being critically important in shifting the δ34S value of degassed melts with respect to the original magmas. During the outgassing, melts above the threshold are depleted in 34S, whereas melts below the threshold are enriched in 34S. In particular, the outgassing of SO2 above the sulphide threshold can produce large negative δ34S values in the degassed melts, whereas the outgassing of H2S below the threshold will strongly drive the δ34S value of the melts in the positive direction. The correlation between δ34S value and sulphur content of total sulphur in the solidified rocks is indicative of the Rayleigh‐type degassing.
Uranium at the Cretaceous‐Tertiary boundary in Denmark
Authors: Kunzendorf Helmar , Gwozdz Rajmond , Hansen Hans Jørgen
Published: July 2007

Uranium is significantly enriched (up to two orders of magnitude) in the Danish Cretaceous‐Tertiary boundary beds relative to the underand overlaying sediments. Both the predominant oxic and some anoxic deposits have a high uranium content. To investigate the geochemical behaviour of the element, a series of sections was analysed for uranium by means of the delayed‐neutron counting technique.

Uranium contents in the carbonate rocks from different parts of the Danish Sub‐basin are generally low but show slight regional trends. Experiments that involve cold acid extractions suggest that uranium is associated with the non‐carbonate residues.

The uranium distribution with depth in the offshore drill core from the Central Graben area (North Sea) suggests that the element is associated with clay in the Danian part.

Cretaceous‐Tertiary boundary beds from Stevns Klint and other localities in the Danish sub‐basin have anomalously high uranium contents compared with the values for chalk. Uranium is not correlated with iron, non‐carbonate carbon or aluminium. The highest uranium values within boundary sections are not found in the lower part of the sections as is the case for iridium.

The only boundary beds that show typical anoxic depositional affinity have a total uranium accumulation that is one order of magnitude lower than that found in the oxic sections.

High amounts of uranium within Cretaceous‐Tertiary boundary beds are suggested to be related to diagenetic processes such as compaction and dehydration.

Uranium is thought not to cause the extinctions at the Cretaceous‐Tertiary boundary because of the relatively low contents found at the actual extinction level.
Heat production and seismic velocity of crustal rocks
Authors: Stegena Lajos G. , Meissner Rolf O.
Published: July 2007

Heat production of the continental crust can be determined from the seismic velocity structure. There is, however, a significant scatter in the determination, partly caused by the quality of geothermal data and partly by the fact that seismic velocity and radiogenic heat production are not uniquely related to each other by the chemical composition of rocks.
Tracing Chernobyl's Fallout
Authors: Gould Peter R.
Published: July 2007

When the third angel blew his trumpet a great star flaming like a torch descended from the sky, falling upon the third part of the rivers and upon the sources of water. The star is called wormwood. The third part of the waters turned to wormwood, and great numbers of men died from drinking the waters because they had been poisoned.
An analysis of the variation in delta architecture
Authors: Postma George
Published: July 2007

The architecture and sedimentary facies of a delta during its steady‐state development varies with the type of distributary system, the basin water depth, and the different ways of sediment diffusion at the delta front. Analysis of these variables has resulted in twelve prototype deltas, which are postulated as sedimentological norms to facilitate comparisons of both modern and ancient delta systems.
Stratigraphy and K‐Ar ages of the Diego Hernández wall and their significance on the Las Cañadas Caldera formation (Tenerife, Canary Islands)
Authors: Marti J. , Mitjavila J. , Villa I.M.
Published: July 2007

The Las Canadas Caldera corresponds to a volcanic caldera formed after a long period of explosive activity. The structural and lithological variations which can be observed in the caldera wall make clear the complexity of the original Las Canadas Edifice in which different eruptive centres existed. The stratigraphic and structural reconstruction of the Las Canadas Caldera indicates that the Diego Hernández wall, located at the eastern side of the caldera wall, comprises the youngest pre‐caldera deposits. Determination of their K‐Ar ages has provided the maximum age for the formation of the Las Canadas caldera. The results are internally consistent with stratigraphic relationships and allow two pre‐caldera volcanic cycles in the Diego Hernández wall to be differentiated in accordance with geological evidence. The first cycle shows imprecise age limits. The second cycle ranges from 0.35 to 0.17 Ma. This upper pre‐caldera age suggests that the Las Canadas caldera and the Teide‐Pico Viejo were formed more recently than was previously assumed.
The origin of magnesite deposits from the Polish Foresudetic Block ophiolites: preliminary δ13C and δ18O investigations
Authors: Jedrysek M. Orion , Halas Stanislaw
Published: July 2007

Twenty‐three magnesite samples from vein deposits, found in ultramafic rocks related to ophiolites in the north‐east Bohemian Massif, have been examined for carbon and oxygen isotope ratios. In these rocks two stages of antigorite serpentinization took place prior to magnesite precipitation. δ18OSMOW in magnesites ranges from 24.5 to 27.9%o (corrected for acid fractionation factor) which leads us to conclude a meteoric origin of the ore‐forming solution. This inference is further supported by δ13C values (−18.7 to −4.4%o) which point to a biogenic origin of carbon in the magnesites.
Resolution of gravimagnetic and radiometric signals by Hilbert Transform
Authors: Ramadass G.
Published: July 2007

Regional gravity, magnetic and radiometric surveys were conducted in the Sunkalagaripalle–Rekhalakunta area of the Cuddapah basin, Andhra Pradesh, India. Since the Geophysical anomalies of this area are of very low amplitude, a new filter Mj, was generated, using the Hilbert Transform in order to enhance the signal from its noisy background. Filter Mj is the summation of the multiplied values of the horizontal derivative of the anomaly and its corresponding Hilbert Transform (or vertical gradient), computed three at a time (three point data window) starting from one end of the profile. The process was repeated by sliding the data window along the entire profile, the Filter Mj was convolved with the first horizontal derivative (Mj×A) and with its Hilbert Transform (Mj, ×H). Resolved gravimagnetic and radiometric signals were then correlated with contacts and faults etc. Such studies are shown to be of value for the qualitative interpretation of noisy geophysical data.
Gold‐antimony mineralization at Loddiswell, Devon, UK
Authors: Stanley C.J. , Halls C. , Camm G.S. , James J.
Published: July 2007

Native gold, in association with tetrahedrite, bournonite, bismuthian jamesonite, antimonian bismuth, chalcopyrite, sphalerite, gersdorffite, galena, covelline, yarrowite and acanthite occurs in a NW‐SE trending quartz carbonate vein which cuts folded Lower Devonian slates of the Meadfoot Group. The locality, 2.5 km north of the village of Loddiswell, lies in a belt of Devonian thrust and nappe terrain with a roughly E‐W trend. The host‐rocks are muddy turbiditic sediments interbedded with spilitic lavas, keratophyres and tuffs, together with intrusive dolerites (greenstones) which were deformed together during the Variscan orogeny.

The deposit was worked briefly in the nineteenth century but little ore was raised and it is doubtful whether any gold was recovered. Analysis of samples collected in the present study revealed gold values of 5‐10 ppm and silver values of 1000‐2000 ppm.

The relationship between gold‐antimony mineralization, the basic igneous rocks in the nappe sequence, and their intersection by a series of major NW‐SE fracture zones is discussed in the context of the regional metallogenic evolution of SW England. The mineralization is considered to be the result of fluid extraction during shear movements on the NW‐SE structures and shows features in common with mesothermal gold‐bearing sulphide veins in other Palaeozoic provinces.
The Archaean gold mineralization in Rämepuro, llomantsi greenstone belt, Eastern Finland
Authors: Ojala V.J. , Pekkarinent L.J. , Piirainen T. , Tuukki P.A.
Published: July 2007

The Rämepuro gold mineralization is situated in the Hattu sub‐belt of the Archaean Ilomantsi greenstone belt, Eastern Finland. It consists of gold‐bearing quartz veins located mainly within the shear zone contact between felsic volcanics and sedimentary rocks. The quartz veins cutting all the types of Archaean rocks are composed mainly of quartz and tourmaline and minor amounts of pyrite, pyrrothite, chalcopyrite, sphalerite, siderite, hedleyite, native bismuth and gold. The highest amounts of gold are found in the quartz‐tourmaline veins, with abundant chalcopyrite and sphalerite. Gold has its best correlation with Bi, Te, S, Zn and Cu. The minor mineralogical alterations (sericirization, saussuritizarion, chloritization) are connected with variations in some major elements. The quartz veins were emplaced under greenschist facies conditions after the peak in the lower amphibolite facies metamorphism.
The gold area of Jales (northern Portugal)
Authors: Neiva J.M. Cotelo , Neiva A.M.R.
Published: July 2007

The hydrothermal gold quartz veins of Jales cut Hercynian granitic rocks, Pre‐Ordovician, Ordovician and Silurian schists. They occur along Hercynian NNE‐SSW, NE‐SW and WNW‐ESE faults and are probably related to the Jales granite. Some are over 2 km long and have a thickness of 0.02–2 m. The only exploited quartz veins are from Campo and Desvio which contain several ore‐shoots (25t Au exploited since 1933). The veins from Jales area also have good Au reserves.

Quartz and arsenopyrite dominate in the gold quartz veins with a banded structure. Electrum and gold are included in sulphides, sulphosalts and quartz and also in veinlets cutting these minerals. Silver occurs in electrum, argentite, galena, freibergite and polyargyrite. Several minerals were analysed by electron microprobe. The primary minerals, some showing recurrences, belong to six paragenetic stages formed between 550 and 30°C and separated by faulting.
A granite window to the lower electrical crust and upper mantle
Authors: Beamish David
Published: July 2007

The structure and properties of the deep crust and upper mantle can be investigated using magnetotelluric observations. Near‐surface and upper crustal complexities may distort or limit the capability of the data to adequately resolve deep structure. Granite batholiths have been regarded as windows into the lower crust in the context of seismic reflection data although the granite bodies themselves are not usually detected. Magnetotelluric data from SW England are here used to demonstrate that, in addition to imaging the internal structure and base of a granite, the batholith itself provides a suitable environment for the effective estimation of the resistivity structure to lower crustal and upper mantle depths.
Evolution of the Western Amazon Lowland Relief: impact of Andean foreland dynamics
Authors: Räsänen M.E. , Salo J.S. , Jungnert H. , Pittman L. Romero
Published: July 2007

The congruency in the depositional origin and age of the uppermost sedimentary strata forming non‐flooded rainforest ground (terra firme) in the western and central Amazon lowlands is a much debated subject. Here we conclude from the study of remote sensing imagery that active Andean foreland dynamics have played a major role in the evolution of the Plio‐Pleistocene fluvial landscape in the western

Amazon. Foreland dynamics have resulted in a terra firme composed of late Tertiary alluvium and younger alluvial terraces and plains. In Peru, thermoluminescence and 14C dating show local aggradation of this younger alluvium between 180 and 30 ka. The documented high age heterogeneity of the terra firme has implications for considerations of the biogeography of the Amazon forest.
Lithospheric extension and the opening of the Red Sea: sediment‐basalt relationships in Yemen*
Authors: Menzies Martin , Bosence Dan , El‐Nakha Hamed A. , Al‐Khirbash Salah , Al‐Kadasi Mohamed A. , Subbary Abdulkarim Al
Published: July 2007

This paper analyses new field and radiometric age data on the timing of extension, sedimentation and magmatism related to the opening of the Red Sea. The first evidence of widespread extension is found in synsedimentary fissures in the fluviatile to shallow marine Tawilah Formation of Cretaceous to early Tertiary age. The first indication of magmatism is the eruption of alkaline basalts (43.5–21.2 Ma) on to marine and non‐marine sandstones of lower to middle Tertiary age. The lack of an angular unconformity at the sediment‐basalt contact, over a period of 25 Myr, corroborates a diachronous relationship between the Tawilah sandstones and the Yemen Volcanics. These data also indicate that the onset of volcanism in Yemen was in the Eocene, as is the case in Ethiopia and Saudi Arabia. A passive rifting model is supported by early extension and sedimentation followed by syn‐ and post‐tectonic magmatism.
Reflection and refraction seismics in areas of complex geology. An example in the Northern Apennines
Authors: Cassinis R. , Lozej A. , Tabacco I. , Gelati R. , Biella G. , Scarascia S. , Mazzotti A.
Published: July 2007

An experimental survey, employing refraction wide‐angle reflection seismic techniques (DSS: deep seismic soundings) was carried out in the Northern Apennines (North Italy).

The main objective of the experiment was the application of DSS to better‐define the structure of the upper crust, down to about 15 km depth, in the crucial Alps–Apennines boundary zone. A second objective was to understand the potential of DSS as a complementary tool in areas of complex geology, where the results of near vertical reflection (NVR) are generally poor.

The results of the experiment show that DSS, if properly planned, can continuously follow deep markers, and therefore impart a greater significance to faint and discontinuous NVR, as well as data on the P– wave velocity of the seismic units.
A new ophiolite occurrence in NW Sudan – constraints on Late Proterozoic tectonism
Authors: Rahman E.M. Abdel , Harms U. , Schandelmeier H. , Franz G. , Darbyshire D.P.F. , Horn P. , Müller‐Sohnius D.
Published: July 2007

Mafic–ultramafic sequences in the Jebel Rahib fold‐and‐thrust belt of NW Sudan comprise the metamorphosed equivalents of obducted oceanic lithosphere. Primary features like pillow‐structures, quenchtextures, igneous layering and primary minerals like chromian spinels and pyroxenes are partly preserved. Geochemical investigations confirm the field evidence and reveal the occurrence of harzburgites, ophiolitic chromites, gabbros, gabbroic cumulates and basalts of primitive tholeiitic compositions resembling transitional MORBs. The age of low‐grade overprint of the basaltic rocks can be limited to 860–740 Myr (K–Ar). The existence of an ophiolite, as well as its close interfingering with highly deformed basin sediments, provides unambiguous evidence for a cycle of extensional and compressional tectonics in NW Sudan during Pan‐African times. Consequently, the concept of an older, stable Proterozoic, or even Archaean, ‘African Craton’onto which the juvenile Pan‐African Nubian Shield assemblages were accreted, needs revision.
Elastic and isostatic subsidence of the Blåsjø artificial lake, Southern Norway
Authors: Fjeldskaar Willy
Published: July 2007

When a load is applied to the surface of the Earth, there is an immediate elastic deformation followed by a time‐dependent isostatic subsidence. The two processes on the Blåsjø artifical lake, Southern Norway are modelled. The isostatic subsidence turns out to be negligible. A comparison of the modelled elastic deformation and the relative land levelling data gives valuable information about the elastic properties of the Earth's upper layers. The elastic parameters inferred from this study are lower than those from seismic investigations, and more in accordance with laboratory experiments.
Geomagnetic reversal history
Authors: Lowrie William
Published: July 2007

The 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

We 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

A 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

Many 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

Stable 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

Results 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

Tornographic 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

Travel‐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

We 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

This 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

Induced 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

Gravity 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

Tertiary 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

The 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

The 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

The 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

Approximately 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

During 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

Minerals 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

Comparison 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

The 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.