bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Kola Superdeep Drillhole and the nature of seismic boundaries
Authors: Pavlenkova N.I. 
Published: July 2007

ABSTRACTThe Kola Superdeep Drillhole was drilled through 7 km of Proterozoic rocks of the Pechenga structure and 5 km of the Archean basement in the Baltic Shield to 12 km depth. The results of drilling revealed a significant heterogeneity of physical properties of the crystalline rocks and a surprisingly high porosity and water content throughout the section. Seismic wide‐angle reflection data, obtained in the region of the hole, were used to delineate the volcanic‐sedimentary layers of the Pechenga structure and the intersecting faults. These studies revealed also a subhorizontal boundary at a depth of 7 km of uncertain origin. Core sampling implies that this boundary is associated with a change in core pressure, with higher porosity and with velocity anisotropy. A change in rock fissuring and in the fluid regime correlates with a velocity inversion zone reached by the hole at a depth of 4.5 km.
The Helice Fault?
Authors: Mouyaris N. , Papastamatiou D. , Vita‐Finzi C. 
Published: July 2007

ABSTRACTThe site of the ancient Greek city of Helice, which was destroyed by an earthquake in 373 bc, has never been found. We propose that it was submerged as the result of seismic slip on a normal fault traceable SE of Egion and that the fault was reactivated in 1881, when Schmidt reported a fresh scarp 2 m high and 13 km in length at the same locality. Earlier movements on the fault are inferred from Lithophaga borings on coastal Sectors of the footwall which yield 14C ages representing over 6.5 m of uplift in the last 4880 years.
En echelon fractures in a dextral shear zone ‐ tectonic heritage for a hydrothermal cave (Budapest, Hungary)
Authors: Fodor L. , Leél‐Össy SZ. , Tari G. 
Published: July 2007

ABSTRACTMicrotectonic study of brittle structures in the József Hill Cave, Budapest, highlights the connection between different phases of fracturing and cave formation. E‐W trending dextral faults (second order Riedels) and NW‐SE oriented tension fractures developed in a ENE‐WSW trending dextral shear zone as a result of WNW‐ESE directed compression. Ascending thermal water dissolved cave galleries and created barite veins along these fractures. The first stage of cave formation as inferred from timing of fracturation from the regional stress field was Oligocene‐Early Miocene. Between the Middle Miocene and Quaternary new N‐S to NE‐SW trending normal faults were formed by ESE‐WNW extension. Pleistocene differential uplift resulted in the reactivation and enlarging of fault zones, dominantly the E‐W trending older Riedels. These recent tectonic events enhanced the original en echelon geometry of the older cave corridors.
The massive stibnite veins of the French Palaeozoic basement: a metallogenic marker of Late Variscan brittle extension
Authors: Munoz Marguerite , Courjault‐Radé Pierre , Tollon Francis 
Published: July 2007

ABSTRACTThe stibnite ore deposits of the French Palaeozoic basement are spatially related to major Late Variscan strike‐slip faults. They occur as small discontinuous veins mostly hosted in epizonal or catazonal siliciclastics. Stibnite crystallizes in the final stage of a polymetallic paragenesis from an antimony‐bearing solution, which deposits a first discrete Fe‐As assemblage at 300–400°C and 0.5–0.8 Kbar. Experimental data have shown that antimony solubility drastically decreases on cooling. Characterization of the Late Variscan antimony‐bearing fluids enables us to predict the temperature range ‐ 270/150°C ‐ under which stibnite was precipitated. Since the latter coincides with the fluid inclusion homogenization temperature range, the pressure at which stibnite crystallized can be estimated from vapour pressure data to have been around 0.1 Kbar.Extensional brittle shear zones, developed at the end of the Late Variscan orogeny (probably at the Westphalian/Stephanian boundary), drained the hydrothermal fluids near to the surface (c. 1000 m ?) reaching the critical P‐T conditions for stibnite crystallization.
Palaeontological and facial features of the Upper Jurassic Hochstegen Marble (Tauern Window, Eastern Alps)
Authors: Kiessling Wolfgang 
Published: July 2007

ABSTRACTMicropalaeontological, microscopic and mineralogical investigations of the ductily deformed and greenschist‐facies metamorphic Hochstegen Marble in the Tauern Window shed new light on its stratigraphy and fades.New radiolarian and sponge spicule discoveries have been made in cherty limestone marbles. They confirm previous age assignments and permit for the first time a more exact micropalaeontological age determination of early Tithonian for the upper parts of the marble. Forty morphotypes of radiolarians could be distinguished; in one sample a Fisher diversity index of 6 is reached indicating deeper marine conditions. The spicule fauna is also diverse and shows affinity to the S‐German Malm. In respect to all the data it can be presumed that carbonate sedimentation of the Hochstegen Marble took place in a deeper marine environment at the southern margin of the European continent (Helvetic realm) during the whole Late Jurassic.
Palynological evidence for Lower Ordovician rocks (Tremadoc and Àrenig) in the Northern Greywacke Zone (Eastern Alps)
Authors: Reitz Erhard , Höll Rudolf 
Published: July 2007

ABSTRACTUntil recently, only fossils of Caradoc to Carboniferous age have been reported from the Northern Greywacke Zone/Eastern Alps. New medium‐preserved and diversified acritarch assemblages from the Lower Wildschönau Formation indicate a Lower Ordovician (Tremadoc and Arenig) age. These fossil spectra define a well‐constrained time interval for a lower section of the Northern Greywacke Zone for the first time.
Ordovician faunas in mass‐flow deposits, Southern Scotland
Authors: Clarkson Euan N.K. , Harper David A.T. , Owen Alan W. , Taylor Cecilia M. 
Published: July 2007

ABSTRACTIn the Ordovician Northern Belt of the Southern Uplands, basal volcanics (Arenig) are followed by cherts (Llanvirn‐?Llandeilo), then by graptolite shales (Llandelio‐Lower Caradoc), and finally by Caradoc greywackes. Within the greywackes (Kirkcolm Formation) are a number of occurrences of fossiliferous conglomerate and overlying mudstone; these can be traced along‐strike for some 30 km.The conglomerates, and especially the mudstones, yield rich mid‐ Caradoc shelly assemblages; brachiopods (20 spp.)/ trilobites (14 spp.), gastropods, bivalves, bryozoans, and the first known Palaeozoic scleractiniamorph coral.These occurrences are interpreted as mass‐flow deposits derived by downslope movement from a now‐vanished shelf to the North, and may belong either to a single gigantic debris flow event, or to a series of smaller, but roughly contemporaneous flows.Strong faunal similarities to faunas at Girvan (western Scotland), and Tyrone (Northern Ireland), lying North of the Southern Upland Fault may suggest sinistral strike‐slip movement of no more than a few hundred kilometres.
The earthquake of 1546 in the Holy Landz
Authors: Ambraseys N. , Karcz I. 
Published: July 2007

ABSTRACTThe earthquake of 1546 is considered to be one of the largest shocks in the Middle East associated with surface faulting and great loss of life. The examination of contemporary documents shows that this seismic event was a medium magnitude earthquake of Ms about 6.0, in many respects similar to that of the earthquake of 1927, that is, one of those early and grossly exaggerated events which excited widespread interest rather on account of the geographical location than because of their size or special violence. We cpud find no evidence of faulting or excessive damage and no justification to regard this earthquake as one of the most destructive in the Jordan Rift Valley.
Oceanographic and climatic implications of the Palaeocene carbon isotope maximum
Authors: Corfield Richard M. , Cartlidge Julie E. 
Published: July 2007

ABSTRACTWe have compared detailed planktonic and benthonic foraminiferal carbon and oxygen isotope records from the Palaeocene and early Eocene successions at DSDP Site 577 (Shatsky Rise, North Pacific), a composite section derived from DSDP Leg 74 sites (Walvis Ridge, South Atlantic) and a composite section from ODP Leg 113 sites (Maud Rise, Weddell Sea). The δ13C records of Palaeocene and early Eocene Foraminifera at Site 577 and the Leg 74 sites show that an increase in δ13C values in surface waters at 64 Ma (end of Zone P1) resulted in increased vertical carbon isotope gradients (δ13C) between surface and deeper dwelling planktonic foraminifera, and between surface‐dwelling planktonics and benthonic foraminifera which became progressively steeper until the iniddle Late Palaeocene (Zone P4). This steepening also occurs in the latest Palaeocene of the composite Leg 113 section and can be explained by an increase in surface ocean productivity. This increase in productivity probably resulted in an expansion of the oxygen minimum zone (OMZ).Benthonic δ13C values increased during the late Palaeocene in Site 577 and the composite Leg 74 section, suggesting that the Palaeocene carbon isotope maximum was composed of both within‐ocean reservoir (increased surface water productivity) and between‐reservoir (organic carbon burial) ftactionation effects. The benthonic δ13C increase lags the surface ocean δ13C increase in the early Palaeocene (63–64 Ma) suggesting that surface water productivity increase probably led an increase in the burial rate of organic carbon relative to carbonate sedimentation. Moreover, inter‐site δ13C comparisons suggest that the locus of deep to intermediate water formation for the majority of the Palaeocene and the earliest Eocene was more likely to have been in the high southern latitudes than in the lower latitudes.Oxygen isotope data show a decline in deeper water temperatures in the early and early late Palaeocene, followed by a temperature increase in the late Palaeocene and across the PalaeoceneEocene boundary. We speculate that these changes in deeper water temperatures were related to the flux of CO2 between the oceans and the atmosphere through a mechanism operating at the high southern latitudes.
Formation and growth of normal faults at the divergent plate boundary in Iceland
Authors: Gudmundsson Agust 
Published: July 2007

ABSTRACTThe divergent plate boundary in Iceland is characterized by 40–80 km long and 5–10 km wide swarms of tension fractures (∼102 m long) and normal faults (∼103 m long). The upper part of the crust is mainly composed of lava flows, with abundant columnar joints that are mostly perpendicular to the lava contacts. The lava flows are horizontal at the surface of the rift zone but become tilted at the rate of 1° for every 150 m depth in the crust. At the surface of the rift zone the joints are vertical and parallel to the vertical principal stress. Because of tilting of the lava pile, the columnar joints become oblique to this stress, hence becoming potential shear fractures, and form echelon sets at greater depths in the crust. Theoretical considerations suggest that normal faults start to nucleate on sets of en echelon columnar joints and/or large‐scale tension fractures at crustal depths of 0.5–1.5 km. The width (depth) must be the smallest (controlling) dimension of many faults. Nevertheless, there is a positive linear relation (r = 0.91) between maximum throw and length of the Holocene faults. If the faults grow as self‐similar structures, the throw‐length relationship can be explained by a similar relation between fault length and width.
Stable isotope geochemistry and structural elements of the Sabina region (Central Apennines, Italy)
Authors: Maiorani† A. , Funiciello R. , Mattei M. , Turi B. 
Published: July 2007

ABSTRACTVarious tectonic features are present in the Meso‐Cenozoic basin units of the Sabina region (Central Apennines, Italy): Mio‐Pliocene northeasterly verging thrusts are followed by Plio‐Pleistocene, N‐S oriented right‐lateral strike‐slip faults. Stable isotope geochemistry and examination of meso‐ and microstructures show that strain conditions differed through the course of tectonic history. Carbon and oxygen isotope analyses of the calate‐filled extensional fractures, the sigmoidal veins present between stylolitic cleavage surfaces, and fault plane surfaces with differing motion, demonstrate those different geneses.The “C/'” C of the older calcite‐filling fractures (present both in the thrust and the strike‐slip systems) suggests a deposition from shallow, fresh water circulation. Furthermore, the calcite fill of en echelon systems, that occur in the southernmost Plio‐Pleistocene units, is clearly the result of a more recent, right‐lateral strike‐slip movement, connected with shallow water circulation within Mesozoic limestones.The sigmoidal vein fills are derived from solid‐state pressure solution processes which were the result of strike‐slip movement. The deformation pattern related to the older thrust system is similar, but less intense; this also demonstrates general recrystallization processes in a closed system.This suggests that the total shortening of the deformed sections is lower than that obtained on the basis of solution on stylolitic planes, because a sigruficant volume of dissolved carbonates remained in the system.Stable isotope analysis also confirms that the deformational history of strongly cleaved rocks in the Sabina region took place in two phases and that extensional fractures formed before stylolithic planes, as suggested by structural and field observations.
On the mechanical properties of synthetic kaolinite/quartz fault gouge
Authors: Rutter E.H. , Maddock R.H. 
Published: July 2007

SUMMARYThe mechanical properties and microstructures of mixed kaolinite/ quartz fault gouge have been studied by means of triaxial tests, wherein a 1 mm thickness of fault gouge was sheared between rigid, sintered alumina sliders. Test conditions ranged up to 200 MPa confining pressure, 175 MPa pore water pressure and temperatures to 600°C. Constant displacement rate tests were carried out at 5×10‐4 mm s‐1, and the stress relaxation technique was used to access a wide range of lower displacement rates down to 10‐10 mm s‐1. The effects of different ratios of clay: quartz were studied, and some experiments were cafried out using crushed Tennessee sandstone gouge and pre‐faulted cylinders of Tennessee sandstone. Deformation‐induced microstructures were studied by optical, scanning and transmission electron microscopy, and mineral chemistry changes were identified using EDS analysis in the STEM.The most important factor determining the strength of these gouges is effective confining pressure, and the effective stress law was obeyed at all test conditions. Increasing the proportion of quartz in the gouge slightly increases the strength, as does increase of temperature. Under all test conditions the gouges deformed by strain‐hardening stable sliding. At 2 mm displacement the friction coefficient is similar to that for rock and rock sliding (μ= 0.85).Over wide ranges of strain‐rate and temperature the strength of these gouges is little affected if the effective pressure is high, but strength drops rapidly with decreasing strain‐rate if effective pressure is low (or if pore water pressure is high).Reloading of the gouge after stress relaxation at high temperatures demonstrated hardening arising from hydrothermal cementation during stress relaxation, which led to sudden rupture of the cemented gouge. This phenomenon may be responsible for cyclic rupture of natural faults.New mineral phases were produced in these experiments only at 600°C. At 400°C, anticipated production of pyrophyllite from kaolinite plus quartz was not found, but recrystallization of kaolinite is believed to have occurred and evidence of healing of cracks in quartz was seen. Microstructural studies revealed the ubiquitous development of P and R1 foliations and other features, which are identical to those found in natural clay‐bearing fault zones. Microstructural evolution is associated with the strain‐hardening, and apparent hardening is strongly associated with the stress path during loading.
Earthquake premonitory processes: Evolution of stresses and electric current generation
Authors: Teisseyre R. 
Published: July 2007

ABSTRACTThe principles and assumptions of the Earthquake Premonitory and Rebound Theory are reviewed. The Theory based on a continuum model of fracturing processes; the stress evolution equations describe the dynamic processes governing a continuous distribution of dislocations.Special attention is paid to the problem of electric current generation in a seismic source zone. Electric current is considered as reflecting the rate of polarization, which is influenced by motion of the charge‐bearing dislocations; the relationship between the current density and stress accumulation rate is derived.
The geological history of insect‐related plant damage
Authors: Stephenson Jonathan , Scott Andrew C. 
Published: July 2007

ABSTRACTBiological damage to plants is commonly found from the Devonian but occurs most commonly from the Cretaceous. Damage inflicted on plants whilst they were alive may trigger a pathological response involving the growth of abnormal tissues. Much of the damage is caused by arthropods, particularly insects. Whilst some damage is non‐taxon specific, such as simple feeding traces, other damage, such as leaf mines, galls or bark boring, may reveal the co‐evolution of host specific taxa and the timing of such interactions. Damaged plants, particularly from the Cretaceous and Tertiary are described and illustrated. The geological history of the evolution of insect‐related plant damage is briefly reviewed. Increased variety in the pathological response of plants is seen from the Cretaceous with the evolution of the angiosperms and diversification of numerous insect groups.
Milankovitch cyclicity recorded from Devonian non‐marine sediments
Authors: Kelly S.B. 
Published: July 2007

ABSTRACTHydrographically closed basins are sensitive to environmental change at all scales, the influence of climate being particularly strong. Some Devonian basins contain non‐marine successions which appear to represent the deposits of such basins. Climatic fluctuations may be recorded by sediments in the form of Milankovitch band cyclicity. Two novel records of climatically related cyclicity are discussed.Well 12/13‐1 in the North Sea penetrates a fine‐grained Old Red Sandstone succession which is thought to be comparable to the largely lacustrine Middle Devonian deposits of the Orcadian Basin which outcrop onshore. The gamma ray log through the Devonian interval reveals periodic large peaks which correlate with U‐rich, fine‐grained intervals deposited during periods of greatest lake expansion. The peaks are cyclical; power spectrum of the gamma ray data reveal periodicities of c. 8 and 40 m, which are thought to correlate with the 21,000 yr (precession) and 100,000 yr (eccentricity) Milankovitch cycles.The Sherkin Sandstone Formation of the Munster Basin, SW Ireland, is a thick (> 1000 m) succession of largely alluvial deposits which were deposited by a terminal fan network. Detailed analysis of channel body sandstones and sedimentary structures contained within them reveals a cyclical variation in the dimensions of the bedforms camed by the channels. The same cyclicity is evident in the proportion of channel deposits. This variation reflects fluctuations in palaeodischarge, probably related to climatic variation. The main cycles are approximately 130 m thick; spectral analysis reveals two further strong periodicities at approximately 36 and 55 m. Estimated sediment accumulation rates suggest that the cycles represent periods of the order of lo4 years. It is proposed that the longer cycles reflect the 412,000 yr orbital eccentricity cycle and that the shorter cycles are either harmonics or components of the 100,000 yr eccentricity cycle.
High‐resolution profile of stable isotopes and iridium across a K/T boundary section from Koshak Hill, Mangyshlak, Kazakhstan
Authors: Sarkar A. , Bhattacharya S.K. , Shukla P.N. , Bhandari N. , Naidin D.P. 
Published: July 2007

ABSTRACTOxygen and carbon isotopes were measured to a high depth resolution in a nannoplankton carbonate sequence spanning the Cretaceous‐Tertiary boundary at Koshak Hill, Mangyshlak Peninsula, Kazakhstan. The boundary is characterized by the presence of a ∼ 1 cm thick clay layer having a sharp peak in iridium concentration with a maximum value of 3.7 ng g‐1. The δ18O data reveal rapid (∼103years) excursion of sea‐surface temperature at the boundary where an initial cold pulse is followed by a persistent warm period. The δ13C data, in contrast, indicate only a gradual change in productivity across the boundary. The observations suggest a biogeochemical scenario for the boundary event pertaining to shallow epicontinental seas.
Fracture in a heterogeneous medium: a network approach
Authors: Reuschié Thierry 
Published: July 2007

SUMMARYFracture in a heterogeneous medium is simulated by a network model. Heterogeneity is introduced by randomly distributing an initial population of cracks on a triangular network of bonds. Each ruptured bond represents a crack. External stresses are applied onto the network and the evolution of the crack population is analysed when the stresses are increased. A crack will propagate to an intact bond if the critical crack extension force is reached. This propagation leads to the coalescence of bonds: crack clusters are formed. When their shapes are complex we approximate them by simpler ones to compute a crack extension force. Crack interactions are introduced by adding for a given bond the contributions of all adjacent dusters. By using this kind of approach combining fracture mechanics and network modelling, we are able to simulate the rupture of a rock specimen under compression/ traction or shear stresses and to give some characteristics of the macroscopic fracture.
The terrane concept and its manifestation by deep reflection studies in the Variscides
Authors: Meissner R. , Sadowiak P. 
Published: July 2007

SUMMARYThe terrane concept is understood as an important extension of plate tectonics and is based on the recognition of allochthonous, mobile geological units. The concept is successfully applied to the Variscides with their wide range of collisional belts. It is mainly supported by the dense deep‐seismic network of DEKORP, which reveals certain reflectivity patterns and succeeds in mapping old and new deep fault zones between the terranes. Variscan terranes are rooted in the ductile lower crust and seem to consist of continental crust only, partly exclusively of rigid upper crust. Oceanic terranes, on the other hand, are always rooted in the asthenosphere. The development of continental terranes and their boundaries depends strongly on their thermal and rheological history. In the case of post‐orogenic collapse with heating and extension of the lower crust, seismic lamellae develop and often truncate former thrust faults.
Earliest stegosaur dinosaur
Authors: Boneham Brian F.W. , Forsey George F. 
Published: July 2007

ABSTRACTRe‐excavation of the type site of the Sharp's Hill Formation (Bathonian, Middle Jurassic) in Oxfordshire, England, has revealed several horizons with disarticulated remains of a species of stegosaurian dinosaur, here considered to be the earliest stegosaur. It is suggested that stegosaurs radiated out from northern Europe in the Middle and Upper Jurassic to the rest of the world. The general stratigraphy of the type site is described, and it is concluded that the stegosaur remains are possibly of earliest Lower Bathonian age. The sediment in which the remains accumulated is considered to represent a drought‐controlled environment.