bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ordovician faunas, island arcs and ophiolites in the Scandinavian Caledonides
Authors: Pedersen R.B. , Bruton D.L. , Furnes H. 
Published: July 2007

ABSTRACTOrdovician faunal data from the Scandinavian Caledonides is tested with new geochemical information from zircons to give U/Pb ages and source origins of volcanic arc and ophiolite sequences. Early Ordovician (Arenig‐Llanvirn), low latitude, Toquima‐Table Head faunas from the upper Upper Allochthon are associated with an island arc system formed adjacent to Laurentia. Contemporaneous mafic magmas were contaminated by crustal material during subduction and associated granites contain inherited zircons of Archaean age. The nearest source for such rocks is on the Laurentian rather than the Baltic side. Higher latitude Celtic province faunas from the upper Upper Allochthon are from one insular site accessible to forms from both Laurentia and Baltica.The late Ordovician low‐latitude Holorhynchus and subtropical Hirnantia faunas occur in overstep sequences above deeply eroded early Ordovician arc complexes. The transgression appears to be coeval with a second generation of spreading‐related complexes. Single detrital zircons from sediments show sources from Archaean, Proterozoic and early Ordovician terranes. This suggests that deposition was in a basin situated along the same continental margin (Laurentia) to which the early Ordovician ophiolite/arc sequences had already become accreted. The late Ordovician faunas link both Laurentia and Baltica at a time of narrowing of lapetus.The new geochemical data together with the faunal information is supported by recent palaeomagnetic studies.
Caradoc brachiopods from the Leinster terrane (SE Ireland) ‐ a lost piece of the lapetus puzzle?
Authors: Parkes Matthew A. 
Published: July 2007

ABSTRACTThe recent re‐collection and examination of brachiopod‐dominated faunas from many localities in the Duncannon Group of the Leinster terrane of SE Ireland, has resulted in an improved age definition of the assemblages and a reassessment of their biogeographical affinities. The Assemblages are almost all Soudleyan to Longvillian (Caradoc) in age, and provide some constraint on the duration of volcanism related to subduction, which may have ceased in the mid‐Caradoc. At this time, they were part of a single Anglo‐Welsh Province which occupied the seas around the Eastern Avalonia plate. The province was composed of well‐established species from earlier Baltic immigrations together with endemics. Connections with the Scoto‐Appalachian and Mediterranean provinces are evident also.
Irish Carboniferous conodonts record maturation levels and the influence of tectonism, igneous activity and mineralization
Authors: Jones Gareth LI. 
Published: July 2007

ABSTRACTOrganic maturation patterns in the Lower Carboniferous of Ireland have been determined from conodont colour alteration indices (CAI) for some 750 localities. Onshore Ireland conodonts record increasing maturation in the Carboniferous rocks from the oil‐window rocks of the north‐east, southwards to the greenschist meta‐argillite regime of the Munster Basin. In detail the Caledonoid trend has a marked influence in the Midlands, whilst in the south sharp variations in CAI are interpreted as being caused by thrusting of the Variscan Orogeny. In the south‐east low maturities in the Wexford Half‐graben indicate that the region was shielded from orogenic stresses, probably by the Leinster Massif. Igneous centres such as the Carlingford Complex and Croghan Hill produce local sites of increased palaeotemperature. Significant CAI variations have also been noted in proximity to major base‐metal orebodies. The CAI results highlight north‐east Ireland and the Wexford Half‐Graben as areas with hydrocarbon potential.
Chernobyl fallout and radionuclide activity in bottom sediments at the River Adige estuary (northern Adriatic Sea, Italy)
Authors: Merlin O. Hieke , Vittori L. Menegazzo , Molinaroli E. , Morani A. , Pelati L. Tassi 
Published: July 2007

ABSTRACTThe artificial radionuclides 137Cs, 134Cs and 106Ru have been determined up to 16 cm deep in two sediment cores collected in March 1988 at the River Adige estuary in the northern Adriatic Sea. Interdependent relations between the properties of the sediment levels and the activity of radionuclides have been investigated using multivariate statistical analysis. The interactions between radiocontaminants and the particulate matter or water phase are discussed during their transfer processes from the river to the estuary and the marine environment. Diffusion phenomena within the sedimentary column have also been considered. The vertical distribution of the artificial radionuclides due to Chemobyl fallout in sediment cores from the River Adige mouth, compared to those from similar estuarine environments in the Adriatic Sea, point out a general rapid accumulation of river‐borne solid material in coastal zones of the North Adriatic Sea.
A 125 Kyr‐long geological record of seismic source repeatability: the Messina Straits (southern Italy) and the 1908 earthquake (Ms 71/2)
Authors: Valensise Gianluca , Pantosti Daniela 
Published: July 2007

ABSTRACTThe occurrence of characteristic earthquakes along segments of major active belts has been described as early as the beginning of the century. The large 1908, Messina Straits, blind normal faulting earthquake provides an opportunity to investigate the repetition of characteristic earthquakes and the persistency of the main features of the fault zone over a time‐scale in the order of 100 Kyr. We have compared seismological and geodetic descriptions of the 1908 rupture process with long‐term crustal deformation recorded at different stratigraphic levels by marine terraces, marine sedimentary units, and landscape features. The wealth of elevated coastal features in and around a region affected by large normal faulting earthquakes indicates that coseismic strain is superimposed on much faster uplift on a regional scale. We investigated in detail the pattern of deformation of the 125 Kyr‐old, lowest emergent terrace, and found that it mimics the pattern of elevation changes observed following the earthquake. This suggests (1) that the 1908 earthquake is characteristic, (2) that its segment boundaries have been stationary during the past 125 Kyr, and (3) that even the locations of the regions of largest coseismic release do not change through many seismic cycles. Based on a comparison between observed heights of the 125 Kyr terrace and 1908 displacements, we estimated an average repeat time of 1000± yr for a 1908‐type earthquake. We also investigated the height, position, age and state of deformation of older terraces, and found (1) that uplift of the region started about 1 Ma and has since continued rather uniformly at 0.9–1.4 mm yr‐1, (2) that during this time the Straits have narrowed at a rate of 10–20 mm yr‐1, and (3) that all the main geomorphic features of the Messina Straits result from the interaction of fast regional uplift, 1908‐type coseismic subsidence, and global sea‐level fluctuations.
A dislocation model of aseismic fault slip under nonuniform friction
Authors: Dragoni Michele 
Published: July 2007

ABSTRACTA model is proposed for studying the mechanical behaviour of faults during their interseismic periods. The model considers a plane fault surface in an elastic medium, subject to a uniform shear stress which increases slowly with time. A1‐D friction distribution is assumed on the fault, characterized by asperities and a weaker zone. The traction vector on the fault plane has an arbitrary orientation: in particular, it can be nonperpendicular to the asperity borders. Aseismic fault slip takes place when the applied stress exceeds the frictional resistance: slip starts in weak zones and is confined by asperities, where it propagates at increasing velocity. Propagation into asperities is characterized by a dislocation front, advancing perpendicularly to the asperity border. Fault slip does not take prate in the direction of traction, except when traction is perpendicular or parallel to the asperity border. The propagation of such aseismic dislocations produces a stress redistribution along the fault and can play a key role in determining the conditions which give rise to earthquakes.
Modelling the Biosphere
Authors: Westbroek Peter , Muyzer Gerard 
Published: July 2007

ABSTRACTProgrammes for the study of global change correctly identify the development of integrated numerical models of earth dynamics as an ultimate goal. But ongoing research and plans for future investigations suffer from a major flaw: they fail to treat life as a global phenomenon. We propose a long‐term strategy for the incorporation of the biosphere as a module into general circulation models (Gas).
Magma mixing processes in volcanic contexts, a thermodynamic approach with the examples of St Vincent Soufrière volcano, West lndies and Cerro Chiquito, Guatemala
Authors: Bardintzeff Jacques‐Marie 
Published: July 2007

SUMMARYDifferent modalities and thermodynamic conditions of magma mixing are compared: heterogeneity and chemistry, temperature and water pressure, volatile (= water) content and water solubility, density and viscosity. Such data are somewhat scarce in the literature.Two case studies have been studied in detail to highlight this review. (1) St Vincent Soufrière (West Indies). Magma mixing may have been a major process in triggering the 1979 explosive phase. All products (whole rock analyses) are basaltic andesite (52.3–56.2 wt% SiO2) but dacitic (60–64 wt% SiO2) glass occurs as micropumice or inclusions in crystals. (2) Cerro Chiquito (Guatemala). A Quaternary extinct dome consisting of dacite (62.5–67.1 wt% SiO2) enclosing 20–30% in volume of basaltic andesitic (54.9–55.3 wt% SiO2) enclaves.The nearly thorough mixing process of case 1 strongly differs from the commingling process of case 2. The main phases may be mafic (case 1) or acidic (case 2). Thermodynamic parameters are calculated using classical geothermometers and formulae. The range of values and errors are estimated (60–80°C in case of temperature). In addition, other processes, such as crystallization of mineralo‐gical phases and fluid vesiculation, may modify thermodynamical conditions. Difference of magma temperature ranges from about 60°C (case 1) up to about 130°C (case 2). Water concentrations of 2.5 wt% in mafic magmas and 4 wt% in acidic magmas, are always lower than the upper limit of water solubility at depths where contrasting magmas were mixed. The difference between the viscosities of the two magmas varies from one order of magnitude up to five.Various mixing scenarios may occur, each of them being linked to different petrological processes including effusive or explosive volcanism as well as plutonism.
The role of transcurrent intra‐arc tectonics in the configuration of a volcanic arc
Authors: Tibaldi Alessandro 
Published: July 2007

SUMMARYField investigations show that Plio‐Quaternary Mexican and Quaternary Ecuadorian volcanic arcs are coeval with intra‐arc transcurrent or transtensional tectonics with motions along faults parallel or subparallel to the arc. This relationship can also be observed in the Quaternary Kamchatka arc. These arcs have an anomalously wide distribution of volcanic centres which cannot be explained simply by a low dip in the subducting lithosphere. Comparison with the intra‐arc tectonics and geometry of other Quaternary arcs reveals that strike‐slip fault zones, parallel to the arc, favour magma rising in a broad surficial zone and may channel magma feeding mainly huge stratovolcanoes.
A revised census of European Late Cretaceous nodosaurids(Ornithischia: Ankylosauria): last occurrence and possible extinction scenarios
Authors: Pereda‐Suberbiola Javier 
Published: July 2007

ABSTRATNodosaurid ankylosaurs illustrate well the differences between European and North American faunal assemblages during the Late Cretaceous. A revised checklist of the nodosaurid specimens from the Late Cretaceous (mainly Campanian and Maastrichtian) localities of Europe reveals a more important diversity than commonly envisaged, with at least two distinct species represented.Struthiosaurus nustriacusand a new nodosaurid from the Basque‐Cantabric Basin were small (body length about 3 m), presumably dwarf insular forms. AIthough a detailed stratigraphic correlation is not yet availabIe, the disappearance orrelationisnotof the nodosaurids in the Western Interior of North America and in Europe may not be simultaneous but asynchronous. If so, the extinction of the Nodosauridae occurred in the latest Maastrichtian andStruthiosaurus couldbe the last representative of the group.
Stratigraphic evidence for the extinction of the ichthyosaurs
Authors: Bardet Nathalie 
Published: July 2007

ABSTRACTThe extinction of ichthyosaurs is not well understood both in terns of time and of causation although it is supposed to have happened at some point of the Late Cretaceous. Four species of ichthyosaurs attributed to the single cosmopolitan genus Platypteygius Huene, 1922 are currently recognized from the Albian and Cenomanian, but after that time only fragmentary remains have been described. A review of these available post‐Cenomanian ichthyosaur remains reveals that all are doubtful either from a stratigraphic or a systematic point of view. Ichthyosaur extinction may be tentatively correlated with the Cenomanian‐Turonian boundary events. During this interval, biological factors such as a break in the food chain attested by severe extinction in marine invertebrates, especially belemnites, may have led to the extinction of ichthyosaurs.
Global change in Earth history: a personal point of view
Authors: Wezel Forese‐Carlo 
Published: July 2007

ABSTRACTThe global changes of the past took place during the progress of geological cycles and marked a drastic passage from an ancient Pangaean regime of continental emergence to a new Tethyan regime of submergence. They occurred with a certain violence and rapidity, and represented critical phases in the destabilization and subsequent reorganization of the geosphere and biosphere. This process resulted in the destruction of certain assemblages (e.g. biotic mass extinctions) and the rise of new ones (e.g. the emergence of new taxa). These major phases of evolution and growth were probably connected to the upwelling of hot mantle material from great depths and a subsequent process of lateral spreading and outward migration of the mantle melt. The ensuing marked increase in mantle activity, degassing and explosive volcanicity produced catastrophic environmental perturbations with turning points in tectonics, global climate, sea level, ocean and atmospheric chemistry, palaeocirculation and palaeogeography.
Relative sea‐level rise and climate change over the last 1500 years
Authors: Varekamp J.C. , Thomas E. , Van de Plassche O. 
Published: July 2007

ABSTRACTWe constructed a detailed relative sea‐level rise curve for the last 1500 years using a novel approach, i.e. charting the rate of relative sea‐level rise using microfaunal and geochemical data from a coastal salt marsh sequence (Clinton, CT, USA). The composition of benthic foraminiferal assemblages and the iron abundance in peats were used to describe shifts in marsh environment through time quantitatively. The resulting sea‐level rise curve, with age control from 14C dating and the onset of anthropogenic metal pollution, shows strong increases in the rate of relative sea‐level rise during modern global warming (since the late nineteenth century), but not during the Little Climate Optimum (ad 1000–1300). There was virtually no rise in sea‐level during the Little Ice Age (ad 1400–1700). Most of the relative sea‐level rise over the last 1200 years in Clinton appears to have occurred during two warm episodes that jointly lasted less than 600 years. Changes from slow to fast rates of relative sea‐level rise apparently occurred over periods of only a few decades. We suggest that changes in ocean circulation could contribute to the sudden increases in the rate of relative sea‐level rise along the northeastern USA seaboard. Relative sea‐level rise in that area is currently faster than the worldwide average, which may result partially from an ocean surface effect caused by hydrodynamics. Our data show no unequivocal correlation between warm periods (on a decaal to centennial time‐scale) and accelerated sea‐level rise. One period of acclerated sea‐level rise may have occurred between about ad 1200 and 1450, which was the transition for the Little Climate Optimum to the Little Ice Age, i.e. a period of cooling (at least in northwestern Europe). Local changes in tidal range might also have contributed to this apparent increase in the rate of relative sea‐level, however. The second period of accelerated sea‐level rise occurred during the period of modern global warming that started at the end of the last century.
Global change and long‐term geomorphology
Authors: Ollier C.D. 
Published: July 2007

ABSTRACTLandscape evolution is on the same time‐scale as global tectonics, biological evolution, and major climatic change. Some features of global change reflected in landscape evolution result from the breakup of Pangaea. Others relate to major climatic changes, and yet others to a major change from a dominantly plains landscape of the Mesozoic to an increasingly mountainous landscape in the Tertiary. Worldwide deep weathering profiles of Cretaceous and early Tertiary age suggest widespread planation and warm, moist climates. Erosion of deeply weathered regolith following the formation of new continental margins and tectonic uplift led to the deposition of unusual mature sediments. Many river patterns can be traced to early Tertiary or older antecedents.Some climatic changes are due to orbital forcing, but others may be related to changing positions of continents, creation of new seaways, or to mountain building. The timing of mountain uplift, climatic changes and biological changes must be resolved to test models of their mutual interaction. Geomorphic input on tectonics, drainage evolution, and deep weathering will be an essential component in dealing with these problems.
Tectonics and global change ‐ inferences from Late Cenozoic subsidence and uplift patterns in the Atlantic/ Mediterranean region
Authors: Cloetingh Sierd , Kooi Henk 
Published: July 2007

SUMMARYQuantitative subsidence analysis for a number of rifted basins in the northern Atlantic/Mediterranean region provides evidence for rapid phases of PlioQuaternary subsidence. The observed acceleration in tectonic subsidence occurs after a phase of general quiescence in subsidence in these basins and deviates from predictions of stretching models. The latter indicate a decay of subsidence with time after Mesozoic‐Tertiary basin formatioh and a slow tectonic subsidence in Plio‐Quaternary times. A possible explanation for the observed patterns of anomalous subsidence could be an increase in the level of intraplate compression in the northern Atlantic region. Intraplate stress changes in the Plio‐Quaternary are related to the dynamics of African/ Eurasian collision processes and a reorganization of spreading directions in the AtlAntic, possibly reflecting a plate reorganization of global nature.It seems that the Plio‐Quaternary record reflects a period of increased levels of neotectonic activity, interplaying with periods of (de)glaciation. Stress‐induced topography in the onshore parts of continental margins, coupled with the stress‐induced subsidence in the offshore deeper parts of the basins, could have contributed to recent phases of uplift in Fennoscandia, augmenting the uplift induced by glacial unloading. Estimates of ice thicknesses are directly inferred from the observed uplift ignoring other driving mechanisms whereas topography plays a crucial role in the dynamics of glaciation. It is, therefore, important to quantdy the interplay of rapid tectonic uplift and subsidence phases with climatic effects during the Plio‐Quaternary.
The Valanginian carbon isotope event: a first episode of greenhouse climate conditions during the Cretaceous
Authors: Lini Andrea , Weissert Helmut , Erba Elisabetta 
Published: July 2007

ABSTRACTLower Cretaceous pelagic carbonates outcropping along the Southern Alps of northern Italy provide a record of Tethyan palaeoceanography as well as of low frequency fluctuations in the global carbon cycle. The carbonate C‐isotope stratigraphy established at five selected localities in the Southern Alps allows an accurate picture to be drawn of the duration and amplitude of the Valanginian C‐isotope event. δ13C values near 1.25–1.50% determined in Berriasian and lower Valanginian sediments are replaced by more pdsitive δ13C values near 3% in the late Valanginian. The carbonate C‐isotope excursion ends in the early Hauterivian with values fluctuating between 1.5% and 2%. The carbonate C‐isotope excursion is accompanied by a positive excursion in the total organic carbon C‐isotope curve. The Valanginian C‐isotope excursion identified in Tethyan sediments correlates with a C‐isotope excursion recorded in the western North Atlantic, in the Gulf of Mexico, and in the Central Pacific (DSDP Sites 534,391,535 and 167). By analogy with the Aptian stage, also marked by a significant positive C‐isotope excursion, the time of positive δ13C values is regarded as a time of accelerated carbon cycling coupled with increased burial rates of organic carbon and detrital material in oceanic sediments. A warm and humid climate, possiblycoupled with a high atmospheric CO2 content and a high global sea‐level, may have triggered the acceleration of the global carbon cycling. In this case the Valanginian C‐isotope event would reflect a first episode of Greenhouse Earth conditions during the Cretaceous.
Strontium isotope stratigraphy in the Late Cretaceous: intercontinentaI correlation of the Campanian/ Maastrichtian boundary
Authors: McArthur J.M. , Kennedy W.J. , Gale A.S. , Thirlwall M.F. , Chen M. , Burnett J. , Hancock J.M. 
Published: July 2007

ABSTRACTIn the Boreal Chalk of northwestern Europe the base of the Maastrichtian Stage is defined by entry of the belemnite Belemnella. In the Kronsmoor section, in northwestern Germany, which is a standard section for the European Chalk, 87Sr/86Sr at the Campanian/ Maastrichtian (C/M) boundary is 0.707723±9 (10). An isotopic correlation of this boundary to the US Western Interior, for which a highly refined cephalopod biostratigraphy exists, suggests that this boundary, as defined at Kronsmoor, occurs within the Baculites jenseni zone. This correlationagrees with the latest placement based on biostratigraphic criteria. On87Sr/86Srcriteria the boundary at Kronsmoor correlates to the English Chalk at Trunch, Norfolk, UK, at a level 3.5 m lower than its position based on biostratigraphic criteria.At Kronsmoor, 87Sr/86Sr increases in a quasi‐linear manner through much of the section, suggesting that, averaged over intervals of 1 Myr, the gross sedimentation rate and temporal rate of change of 87Sr/86Sr were approximately constant through the section. For US samples, zonally‐plotted values of 87Sr/86Sr define a quasi‐linear trend, which suggests a moderate uniformity of zonal duration from the Baculites compressus zone (73.2±0.7 Ma, 10) to the Baculites grandis zone (70.1±0.7 Ma, 10).