bluuebunny/crossref_metadata_2025_split huggingface dataset:
The palaeobiogeography of Permian anomodonts
Authors: King Gillian M. 
Published: July 2007

ABSTRACTIt is generally considered that the oldest anomodont mammal‐like reptiles are known from Late Permian sediments of the USSR and that during the rest of the Late Permian distribution of these fossils widens to encompass nearly all geographical areas by the end of the Period.This study reviews the occurrence of anomodont genera in Permian sediments and reassesses the conventionally accepted distribution pattern. A broad correlation of terrestrial Permian rocks from different continents is attempted. Using recent reconstructions of Permian continental positions the effect of latitude on anomodont distribution is investigated. Some explanations for the restrictions operating on anomodont distribution are suggested.
Palaeogeographic and geodynamic evolution of the Gondwana continental margins during the Cambrian
Authors: Courjault‐Radé Pierre , Debrenne Françoise , Gandin Anna 
Published: July 2007

SUMMARYDuring the Cambrian, two types of continental margins occurred around Gondwana. The eastern margin (Antarctica, Australia and southern South America) was characterized by a narrow continental shelf with a steep slope separating the shallow water environment from a deep‐oceanic one accompanied by mafidultramafic volcanics. The western margin was characterized by a wider continental shelf, probably passing gradually to an unknown outer basin. This comprised three main domains: the Asiatic shelf, composed of distinct cratonic blocks, presumably separated from each other by deeper‐water/ volcanic intracontinental basins; the European shelf, characterized by the development of shallow intracontinental siliciclastic basins; and the Americanc‐African shelf, morphologically and depositionally uniform. The distinction of these two Gondwana continental margins expresses their different geodynamic behaviour during Cambrian extensional tectonics. In fact, the sedimentary/palaeogeographic evolution, suggests the establishment of an active Pacific‐like margin in the eastern domain, and the tentative establishment of a divergent Atlantic‐like margin, in the westem one.
Infrared spectroscopy of Triassic conodonts: a new tool for assessing conodont diagenesis
Authors: Nöth Sheila , Richter Detlev K. 
Published: July 2007

ABSTRACTThe Fourier transform infrared spectra of individual conodonts with various CAI values indicate definite changes in conodont francolite during diagenesis. Steady decarbonation can be observed in the increasing intensity of the band with the wavenumber 2340 an‐1, which is assigned to trapped molecular CO2. Carbon dioxide originates from decomposing CO2‐3‐ions occupying the B‐site in francolite. Furthermore, the intensity of the water‐deformation band at 1644 cm‐1 decreases with higher CAI values. These changes of intensity can be quantified by calculating the maximum extinction (Emax) for the corresponding absorption maxima and correlated with the CAI. Unaltered conodonts have a relative variable water ‘content’ and very little CO2. Up to a CAI value of 4 conodont francolite continuously expells water and carbon dioxide is trapped. Conodonts with CAI = 5 have similar water ‘contents’ to CAI = 4 conodonts, but decarbonation continues to take place during this stage of diagenesis.
On the migration of precursors of strong earthquakes
Authors: Bella F. , Biag P.F. , Caputo M. , Monica G. Della , Ermini A. , Sgrigna V. 
Published: July 2007

ABSTRACTIt is found that perturbations presumedly associated with swarms, the B patterns and the BG pattern precursors of strong earthquakes in New Zealand, California and Apennines, propagate in the crust of the Earth with a velocity of the order of cm1. The hypothesis that a single travelling elastic perturbation causes a set of precursors of the same strong earthquake is discussed and it is concluded that each precursor is associated with a different perturbation.
Seismic imaging of Pleistocene deep‐sea cyclothems: implications for sequence stratigraphy
Authors: Carter R.M. , Cartef L. 
Published: July 2007

SUMMARYPlate collision along the New Zealand Alpine Fault since the late Miocene has resulted in an abundant supply of temgenous sediment to an adjacent starved late Cretaceous rift‐basin, the Bounty Trough. During the late Neogene, alternating pulses of temgenous (glacial) and biogenic (interglacial) sediment were deposited in the trough in the form of deep‐sea cyclothems, in sympathy with glacio‐eustatic sea‐level fluctuations. Individual cyclothems ranging up to 15 m in thickness have been directly imaged by both 3.5 kHz and single channel airgun profiling. They are particularly conspicuous on the continental slope and in areas of the trough under the influence of overbank turbidite deposition from the Bounty Channel. On the abyssal Bounty Fan, approximately 50 cyclothems have been deposited since the late Pliocene, i.e. each cyclothem corresponds to two contiguous oxygen isotope stages. Each cyclothem also corresponds to the offshore conformity of a single 5th or 6th order seismic sequence, with the lower, temgenous portion marking a lowstand systems tract, and the upper, biopelagic part representing the transgressive and highstand systems tracts. Therefore, as a single continental margin sequence is traced seawards it passes from unconformity‐bounded shelf and shelf‐margin cyclothems, to slope sediments which include thick conformity‐bounded cyclothems or autocyclic canyon deposits, to thin conformity‐bounded deep‐sea cyclothems on the distal rise, and finally to cryptically cyclic biopelagic sediment andor red clay on the abyssal plain.
Stable isotope differences among morphotypes of Neogloboquadrina pachyderma (Ehrenberg): implications for high‐latitude palaeoceanographic studies
Authors: Healy‐Williams Nancy 
Published: July 2007

SUMMARYThe stable isotopic composition of planktonic foraminifera plays a paramount role in interpretations of past oceanographic and environmental conditions; thus an accurate understanding of the factors which influence their isotopic composition is essential. In order to increase the palaeoceanographic utility of the high‐latitude planktonic foraminifera Neogloboquadrina pachyderma, its shape and oxygen and carbon isotopic variability are quantitatively described in this study. Over 8200 specimens of N. pachyderma from 36 gravity and piston core tops from surface sediments of the North Atlantic and southern Indian Oceans were digitized and analysed via Fourier series in closed form. The morphological results are presented in detail elsewhere and are utilized in this study to select specimens for isotopic analyses. Significant isotopic differences exist between morphological variants of this important high‐latitude speaes. Specimens become depleted in both oxygen and carbon isotopes as the test shape becomes more pentagonal and less quadrate. The isotopic differences cannot be attributed to test thickening nor to size or coiling direction. This observation has important implications in the use of this speaes as a tracer in high‐latitude palaeoceanographic investigations. In particular, future isotopic investigations utilizing this species should analyse single forms to allow for clear interpretation of palaeoceanographic signals.
Tectonic episodes of cratons: conflicting North American concepts
Authors: Sloss L.L. 
Published: July 2007

ABSTRACTOver the past one hundred years North American geologists have been influenced by concepts of Earth history based on periodic events involving marked (‘Neocatastrophic’) changes and competing concepts involving steady‐state (‘Uniformitanan’) behaviour. T.C. Chamberlin, a late 19th‐/early 20th‐Century exponent of a nonuniformitarian scenario of earth history, proclaimed ‘diastrophism as the ultimate basis of correlation’ ‐ meaning that geological history is punctuated by orogenic paroxysms causing retreat of epicontinental waters to oceanic basins, creating segmentation of the stratigraphic and chronological record. At mid‐Century James Gilluly gained wide support for the proposition that orogeny has followed a Uniformitarian, near‐steady‐state course. Accordingly, episodic diastrophism is a myth and cannot be the basis for periodic eustatic sea‐level change, interregional unconformities, etc.In more recent decades two powerful new influences on geological thought have emerged. The global tectonic paradigm has forced upon us the realization that rearrangements of lithospheric plates are capable of changing the freeboard of continents. At the same time technological advances in the acquisition and processing of seismic‐reflection data have been seized by receptive minds to organize the newly available stratigraphic imagery for application to the discipline of seismic stratigraphy which emphasizes the identification and correlation of unconformity‐bounded successions of strata. Expansion of the methodology to the outcrop, beyond the limitations of seismic resolution, has brought about the flowering of the New Sequence Stratigraphy, doctrine that has deservedlyachieved wide application and acclaim. Practitioners of sequence stratigraphy, impressed by the distances over which unconformity‐bounded stratal units can be correlated, hew to the belief that eustatic (commonly glacially engendered) sea‐level change is the control.This paper examines evidence of tectonic episodes affecting cratons and their margins. These offer promise of a more satisfactory understanding of stratigraphic sequences and of the Earth history they represent. Consideration of these matters makes it inescapable that the elevation and subsidence of cratons (and their component basins and arches) reflect tectonic phenomena of the continental lithosphere quite independent of eustatic events.
From high plateaux to marginal basins: the active role of the mantle
Authors: Wezel Forese‐Carlo 
Published: July 2007

ABSTRACTCurrent geodynamic models pose many serious problems for the description of continental tectonic processes, Serious difficulties arise also in the description of some of the ocean basins.Deformation of the Earth's crust appears to be concentrated along several mobile megashear belts. It is proposed that these could be the surficial expression of ‘mantle chimneys’ which extend to great depths. Within these structures, post orogenic high plateaux form, and as time passes these develop a central depression enclosed within arcs or indeed full‐scale rings of mountains. The enlargement and deepening over time of the back‐arc depression occurs in concert with the radial migration of a ‘topographic wave’. In this respect, the following structures represent different phases in an evolutionary sequence: (a) the Tibetan Plateau, (b) the North American Cordillera, and (c) the Tyrrhenian Basin and Calabrian Arc. The development of this succession reflects a particularly high degree of activity in the mantle, in which diapiric rising of asthenospheric matter elevates the land and causes tensional rifting. The resulting centrifugal movement of the mantle melt results in crustal foundering and engulfment of the area behind the arc, which thus becomes susceptible to the subsequent processes of com‐pressional deformation.
Geophysiology of mineral deposits ‐ a model for a biological driving force of global changes through Earth history
Authors: Krumbein W.E. , Schellnhuber H.‐J. 
Published: July 2007

ABSTRACTThe upper mantle, crust, hydrosphere and atmosphere of Earth are kept in a geophysical, geochemical and thermodynamical state far from astrophysical and planetary equilibrium. The system oscillates around a quasi‐stable centre following laws governing dissipative or dynamic systems. The energy and materials necessary for such global pseudo‐equilibria are fed in, stored and released on a geological time‐scale by (a) the energy and electron channelling processes of photosynthesis, respiration and fermentation, (b) biologically controlled accumulation of energy and matter into crustal reservoirs and much later (c) release of the latter from crust and upper mantle into surface‐related geotectonical and geochemical cycles. Phototrophic and chemorganotrophic bacterial microorganisms of microbial mats, potential stromatolites or microbialites are capable of anoxygenic and oxygenic photosynthesis, of aerobic and anaerobic respiration and of organic and inorganic fermentation, i.e. disproportioning of energy‐rich molecules. In this way large amounts of photosynthate are transformed on a global scale into hydrocarbons and sulphides (sulphate serving as electron acceptor for anaerobic respiration or fermentation). Inorganic reduced compounds produced by the same processes of photosynthesis followed by respiration and fermentation are stored as sulphides of iron, lead, zinc, silver, gold etc. All the aforementioned microbial processes can transfer energies and matter at a global scale. Thus disparities of the Earth's crust and mantle from the geochemical equilibrium may not be caused solely by internal temperature, radioactivity and gravity gradients, but increasingly by life processes. The biogenic formation of energy‐rich compounds on a global scale delivers huge amounts of energy and electrons to the crust, which are recycled through geological time. The quantities of energy involved appear in themselves to be sufficient to provide the driving force for geotectonic processes. Thus, a model of geophysiological equilibration of geochemical cycles and geotectonics is proposed in which the biota play the role of energy and matter transmitters for geodynamic processes. Living matter controls and transfers more than 10% of the Earth's mass in this system with turnover times of up to 500 million years. The transfer speed of each individual atom according to the model must have gradually decreased since the Precambrian, while the amounts of energy and matter stored and cycled have in turn increased, as also witnessed by the increase in the thickness of the crust. Earth as a bioplanet has come of age.
Carbon sources in arc volcanism, with implications for the carbon cycle
Authors: Varekamp J.C. , Kreulen R. , Poorter R.P.E. , Van Bergen M.J. 
Published: July 2007

ABSTRACTNew CO2/3 He data from the East Sunda Arc (Indonesia) confirm earlier observations that arc volcanic gases have higher CO2/3 He ratios than MOR environments.On average, > 80% of arc volcanic CO2 is recycled, exogene carbon. Addition of a few percent of carbonate‐bearing sediments to the mantle wedge explains much of the carbon abundance andcarbon isotopic data of arc gases, but can not explain the He isotope observations. The CO2/3He in arc volcanoes is not strongly dependent on the composition of modem trough sediments (e.g. deep sea clays vs carbonate‐rich sequences), and calcite veins in the hydrothermally altered subducted slab may provide a contribution to the recycled carbon flux of, arcs. The sum of globally deep‐subducted sediment and slab carbon exceeds the estimated arc CO2 flux, and approximately 3.5 teramole of carbon may return annually to the mantle in convergent zones. The modem combined processes of MOR volcanism, slab alteration, and subduction volcanism do not produce a substantial carbon flux into the exosphere, and rate‐changes in ocean floor spreading are unlikely to cause major changes in atmospheric CO2 as a result of changes in the volcanic CO2 fluxes. Intense pulses of flood basalt volcanism, however, may alter the CO2 contents of the atmosphere over the course of a millenium or so, and influence global climate.
An investigation by transmission electron microscopy of planar deformation features in naturally shocked quartz
Authors: Goltrant Olivier , Doukhan Jean‐Claude , Cordier Patrick , Courtillot Vincent 
Published: July 2007

ABSTRACTWe have investigated by Transmission Electron Microscopy (TEM) the planar deformation features(PDF) in quartz from various sites where shock metamorphism has been detected optically: impact sites; the Vredefort complex (South Africa) and the K/T boundary at Raton Basin (Colorado). PDFs are straight narrow bands of glass or microtwins or huge densities of dislocations. Such contrasting microstructures must reflect different shock scenarios. In the Vredefort complex the post‐shock thermal history has strongly overprinted the shock‐induced defects. In the Raton Basin samples very tiny bubbles have precipitated on the dislocations, strongly suggesting a lengthy annealing at moderate pressure and temperature. This new information should be taken into account in any model of the origin of the K/T transition. In any case, observation of PDFs by optical microscopy alone is not sufficient to unambiguously conclude on their origin.
Investigations on geomagnetic reversals in Icelandic lavas, 1953–78
Authors: Kristjansson Leo 
Published: July 2007

ABSTRACTRecent reviews of the development of palaeomagnetic techniques in geology have shown that palaeomagnetism has contributed significantly to the acceptance of new concepts in global tectonics. The present paper extends Frankel's (1987) review of palaeomagnetic work on the basalt lava sequences of Iceland in the early 1950s. These lavas provide some of the most complete series of reliable ‘spot readings’ of the geomagnetic field available. It is shown that research on Icelandic basalts has continued to be of importance in improving our understanding of palaeomagnetism and its applications.
Eocene age of eclogite metamorphism in Pakistan Himalaya: implications for India‐Eurasia collision
Authors: Tonarini Sonia , Villa Igor M. , Oberli Felix , Meier Martin , Spencer David A. , Pognante Ugo , Ramsay John G. 
Published: July 2007

ABSTRACTA geochronological investigation of two rocks with an eclogitic assemblage (omphacite‐garnet‐quartz‐rutile) from the High Himalaya using the Sm/Nd, Rb/Sr, U/Pb and Ar/Ar methods is presented here. The first three methods outline a cooling history from the time of peak metamorphism at 49±6 Ma recorded by Sm/Nd in garnet‐clinopyroxene to the closure of Rb/Sr in phengite at 43±1 Ma and U/Pb in rutile at 39–40 Ma. The Sm/Nd isotopic system was fully equilibrated during eclogitization and has not been disturbed since; its mineral ages may date the peak metamorphic conditions (650±50°C at 13–18 kbar: Pognante and Spencer, 1991). The Ar/Ar data reveal the presence of substantial amounts of excess 40Ar in hornblende, and yield a statistically acceptable but geologically meaningless phengite plateau age of 81.4±0.2 Ma, inconsistent with Sm/Nd, Rb/Sr and U/Pb. This questions the use of such a chronometer for the dating of high‐pressure assemblages. The results imply a Late Palaeocene or Early Eocene subduction of the northern Indian plate margin in NW Himalaya. The fact that eclogites are restricted to NW Himalaya may be the result of a peculiar p‐T‐t path associated with a high convergence rate during the first indentation, in contrast to the later and slow subduction in Central and Eastern Himalaya.
Hydrothermal alteration of basic island‐arc volcanic rocks north and south of Mytilini Town, Lesvos Island, Greece
Authors: Kelepertsis A.E. 
Published: July 2007

ABSTRACTThe mobilities of major and trace elements have been investigated in hydrothermally altered volcanic rocks of Pliocene age on the island of Lesvos. One type of hydrothermal assemblage, montmorillonite‐K‐feldspar‐goethite, was recognized in outcrops north of Mytilini town.The alteration occurs a few metres under the surface of unaltered volcanic rocks of high‐K andesite and high‐K basaltic andesite composition. The unaltered latite‐andesite consists of plagioclase, clinopyroxene, sanidine and magnetite with quartz, calcite, pumpellyite and montmorillonite as subordinate secondary minerals.The main control over major oxide distribution appears to be the extent of conversion of plagioclase to K‐feldspar.Three distinct groups of elements were revealed to be positively correlated:

Si, Mg, Ca, Na, Mn, Sr and Ba, which are leached during the alteration process. This group of elements reflects their association with plagioclase feldspar and clinopyroxene.
Fe, K, Ti, P, Nb, Zr, Y, Rb, Ni, Cr, V. This group includes elements which are enriched relative to the unaltered volcanic rock, reflecting their association with K‐feldspar, iron hydroxides and Ti and P‐bearing minerals.
Ti, P, Nd, La, Ce. From this group of elements it is indicated that Nd, La and Ce are associated with Ti‐ and P‐bearing minerals.

There is no evidence of Cu or Zn addition to the system by hydrothermal fluids since there are no correlations between these base metals and elements enriched in the K‐feldspar, montmorillonite‐rich zone. This potassic rich zone may be connected with hidden epithermal sulphide mineralization with gold.
Taxonomy and stratigraphic occurrence of Thalassiosira tetraoestrupii sp. nov. and related species in upper Miocene and lower Pliocene sediments from the Norwegian Sea, North Atlantic and North West Pacific
Authors: Bodén Per 
Published: July 2007

ABSTRACTThree new Thalassiosira species are described. Thalassiosira baldaufii and T. labimarginata have previously never been reported whereas specimens of T. tetraoestrupii have probably often been assigned to T. oestrupii (Ostenfeld) Hasle (Fryxell and Hasle) in previous studies. The description of Thalassiosira praeoestrupii Dumont Baldauf and Barren is emended.Quantitative analysis of these Thalassiosira species has been completed for upper Miocene and lower Pliocene sediments from three different regions in the northern hemisphere. The material used is from DSDP Hole 552A in the North Atlantic, Site 578 in the NW Pacific and ODP Site 642 in the Norwegian Sea. The abundance patterns (number of valves per gram dry sediment) obtained allow the assessment of the biostratigraphic significance and precision of specific diatom events. Levels of reliability are estimated based on the degree of abundance change at the critical stratigraphic interval, level of abundance, consistency of occurrence and duration of consistency. The chronology of the events is obtained through direct correlation to the established magnetic polarity history.The following four first‐order reliability (R1) diatom datums are proposed: in the North Atlantic the first abundant occurrence (FAO) of T. praeoestrupii (5.34 Ma), in the Norwegian Sea, first consistent occurrence (FCO) of T. tetraoestrupii (5.00 Ma), FCO of T. praeoestrupii (5.00 Ma) and last consistent occurrence (LCO) of T. baldaufii (4.30 Ma). Two R2 diatom datums are proposed: in the Norwegian Sea, FCO of T. baldaufii (5.13 Ma), LCO of T. praeoestrupii (4.87 Ma). Three R3 diatom datums are proposed: in the NW Pacific, FCO of T. tetraoestrupii (5.02 Ma) and FCO of T. praeoestrupii (5.54 Ma): in the Norwegian Sea, the first occurrence (FO) of T. labimarginata (5.83 Ma).
Ocean Bottom Seismographs used in a crustal study of an area covered with flood‐basalt off Lofoten, N. Norway
Authors: Mjelde R. , Sellevoll M.A. , Shimamura H. , Iwasaki T. , Kanazawa T. 
Published: July 2007

ABSTRACTSeismic refraction measurements were made in August 1988 to study the crustal structure off Lofoten, Northern Norway. Twenty‐four 3‐component Ocean Bottom Seismographs (OBS) were used, of which seven were deployed in the area covered by landward‐flowing basalt deposited during the early Eocene break‐up between Norway and Greenland. The main purpose of the OBS survey was to investigate whether this method can be used to map structures below the basalt, which is not easy to penetrate with conventional seismic reflection techniques. The records obtained showed that the OBS data contain considerable information about structures below the flood‐basalt; preopening sediments up to 4.0 km thick is indicated below the 1.0–2.5 km‐thick landward‐flowing basalt. The success of the OBS survey indicates that such measurements can become an important tool in investigations on passive volcanic margins and, potentially, in other areas where highly reflective boundaries make the reflection technique difficult to apply.