bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stratigraphic correlation of late Palaeocene sand deposits in the Søgne Basin area of the Danish and Norwegian central North Sea
Authors: Danielsen Mette , Clausen Ole Rønø , Michelsen Olaf 
Published: July 2007

ABSTRACTA stratigraphic analysis of late Palaeocene sands of the Søgne Basin and the western part of the Norwegian–Danish Basin shows that the sand bodies are of differenct ages. The geographic distribution of the sand deposits shows that they are related to underlying Mesozoic structures suggesting a controlling effect of Tertiary tectonics on the deposition of sand during the late Palaeocene. However, the structural setting of various sand bodies varies from reactivation of older faults and reactivation of salt structures. The local character of the structures active during the late Palaeocene introduces minor depressions with no lateral connection. The sand bodies, which are interpreted as having been deposited in these depressions, are thus in general separate bodies with no lateral connection. The Fennoscandian shield and eroded Mesozoic sediments along the Fennoscandian Border Zone are suggested as source area for the late Palaeocene sand deposits.
Improved seismic velocity reference model from local earthquake data in Northwestern Italy
Authors: Kissling E. , Solarino S. , Cattaneo M. 
Published: July 2007

ABSTRACTResolution and reliability estimates of results obtained by seismic tomography strongly depend on the reference model. Inadequate initial reference models may severely distort tomographic images or introduce artefacts that lead to misinterpretations of the results. Reference models are usually obtained by means of a priori near‐surface geological information or by geophysical information derived by controlled‐source seismology.Starting from the idea that a reference model must approximate the weighted average of data selected for the three‐dimensional (3D) inversion, one‐dimensional (1D) model for Northwestern Italy is derived that is able to minimize mean of RMS of a set of well‐locatable earthquakes, by computing a solution of the coupled hypocentre 1D velocity problem.Such a model, termed the Minimum 1D model, can be used both as an initial reference model for 3D inversion and as a reference velocity model for high‐quality routine earthquake location.
The North Tyrrhenian–Northern Apennines post‐collisional system: constraints for a geodynamic model
Authors: Bartole Roberto 
Published: July 2007

ABSTRACTThe North Tyrrhenian–Northern Apennines post‐collisional system (NTAS) has been analysed on the basis of marine reflection profiles and bibliographic sources with the aim of providing an up‐to‐date geotectonic and evolutive framework consistent with structural data. The continental rifting began to affect the most internal (western) side of the system in the middle (?)‐upper Miocene, while the most external (eastern) zones were touched by rifting only in Pleistocene times. The birth and development of extensive, asymmetric basins took place with a progressive speeding up of rifting towards the external sectors.A diachronous, regionally extended and eastward rejuvenating unconformity, recognizable within the Neogene–Quaternary basins, marks the passage from the syn‐rift to the post‐rift tectonic regime. While the first is everywhere dominated by extension, the second one produces vertical movements. Reflection terminations related to this unconformity are interpreted in terms of vertical tectonic component. Three zones that experienced different post‐rift vertical movements are thus recognized in the NTAS: subsidence in the North Tyrrhenian deep water region; tectonic stability or alternation of moderate subsidence and uplift in the continental shelf and western Tuscany, strong uplift in eastern Tuscany.The updated structural data demonstrate that the NTAS upper crust is crosscut by both Tyrrhenian‐dipping and Apennine‐dipping low‐angle detachment planes, above which the upper crustal blocks rotated and experienced extensional transport along two opposite directions: to the west and to the east, respectively. The coexistence of opposite‐dipping crustal surfaces bears two fundamental implications for the NTAS geodynamics. First it stresses the importance of the anti‐Apennine transfer faults, since they separate crustal blocks of opposite extension polarity. Secondly, it testifies that the extension tectonics not only re‐utilized former crustal thrust planes, but also gave origin to new significant E‐ and NE‐dipping detachment planes.Plan and crossview geometries of faults, together with considerations on the role of the metamorphic core complexes, point to an interpretation of the NTAS structure that is more consistent with the ‘anastomosing shear’ model rather than the 'simple shear' or the ‘delamination’ ones.
The eclogitized pillows of the Betic Ophiolitic Association: relics of the Tethys Ocean floor incorporated in the Alpine chain after subduction
Authors: Puga E. , de Federico A. Diaz , Demant A. 
Published: July 2007

ABSTRACTIn the volcanic sequence of the Betic Ophiolitic Association (BOA) volcanic structures and textures are preserved in spite of being metamorphosed to the edogite facies. The original quenched glassy margins of the pillows and lava flows are still recognizable by the darker colour, fine‐grained textures and scarcity of phenocrysts. The BOA eclogitized pillows have chemical compositions very similar to the basalts enriched in LIL elements erupted nowadays at the mid‐oceanic ridges. Magmatism which generated the BOA most likely began under continental rift conditions at the Triassic‐Jurassic boundary and continued under ocean‐floor extensional conditions during the lower and middle Jurassic. In age and petrological characteristics this magmatism is equivalent to that of the western Tethys ophiolites. During the Late Cretaceous, due to the collision of African and Iberian Plates, the BOA ophiolites were subducted and underwent a metamorphism in the eclogite fades whose climax in the Lugros outcrop can be estimated at 650–700°C and about 20 kb.
Escape models of the Alpine‐Carpathian‐Pannonian region in the light of palaeomagnetic observations
Authors: Mauritsch Hermann J. , Márton Emö 
Published: July 2007

ABSTRACTRecent tectonic models of the Alpine‐Carpatho‐Pannonian region (ALCAPA) assume a large eastward shift of the Transdanubian Range domain, in the Cenozoic. Since palaeomagnetism is one of the most powerful tools in solving geodynamic processes, the authors present an approach to the escape problem by using all available and relevant palaeomagnetic data. This data set demonstrates consistency with models put forward by geologists for Jurassic and older ages. From the mid‐Jurassic on the Northern Calcareous Alps (NCA) did not share the rotations of the Transdanubian Range domain and of the Southern Alps. After individual movements from Neocomian to Miocene, the Transdanubian Range domain must have drifted northward in the mid‐Miocene up to the Southern margin of the Northern Calcareous Alps, before starting the escape in the geologists' definition.
Crustal Stress in the northern North Sea as inferred from borehole breakouts and earthquake focal mechanisms
Authors: Lindholm C.D. , Bungum H. , Bratli R.K. , Aadnøy B.S. , Dahl N. , Tørudbakken B. , Atakan K. 
Published: July 2007

ABSTRACTThe regional stress field in the northern North Sea (offshore western Norway) has been studied through the acquisition and analysis of directions of maximum horizontal compression (s̀H) as extracted from borehole breakouts and from earthquake focal mechanism solutions.The results indicate that the regional stress field is dominated by NW‐SE compression, with good consistency between shallow borehole breakouts (2–5 km depth) and deeper earthquakes (10–25 km depth). The broad spatial consistency in stress direction indicates that the main stress field is related to factors of primarily plate tectonic origin, and the results are in good agreement with the western Europe trend found in earlier investigations.The Tampen Spur region in the northern North Sea has been subjected to particularly complex deformation, with two dominating fault directions trending NW‐SE and NE‐SW. From Tampen Spur in the west to the Sogn graben in the east an anomalous stress field is indicated, with NE‐SW oriented maximum horizontal compressions. This anomaly is clearly seen both in the borehole breakout data and in the earthquake data. Possible sources for this anomaly are discussed, and include postglacial uplift and/or lateral variations in the physical properties of the crust.
Quantitative models of very high fluid pressure: the possible role of lateral stresses
Authors: Bour Olivier , Lerche Ian , Grauls Dominique 
Published: July 2007

ABSTRACTBecause of the occurrence of very large observed overpressure in a well located in SE Asia, numerical modelling has been undertaken to evaluate evolution of the sediments. The intensity of the excess pressure, close to lithostatic pressure, and the likely relation to induced, open‐fracture anomalies, as well as evidence of large fluid transfers, all lead to the suggestion that the tectonic regime is related to the generation of high excess pressure. To verify this hypothesis, a 2D fluid‐flow/compaction model (GEOPETTI) was used to test whether high excess pressure could be obtained without considering the effect of lateral stresses. While high excess pressures are possible, even if undercompaction is the only process considered, the distribution of fluid pressure with depth does not correspond to that observed, and the migration of fluids cannot be reproduced because of the extremely low permeability of the sediments. Accordingly, the model has been modified so that the effect of lateral stresses can be investigated through: (1) the value of the fracturing coefficient which controls the maximum overpressure that it is possible to generate; (2) the sensitivity of the system to a possible compressive event, which could squeeze the sediments laterally so that the rate of fluid expulsion would be greater than if the fluids were driven only by the mechanical load of sediments. Finally, the role of faulting or fracturing is discussed as a possible mechanism responsible for the upward transfer of fluid which can lead to an increase of excess pressure at depths shallower than the depth where excess pressure was first generated, a mechanism also leading to high excess pressure. Moreover, this mechanism allows for a good reproduction of observed excess pressure distributions.
Interaction between seismic and volcanic deformation: a possible interpretation of ground deformation observed at Vulcano Island (1976–84)
Authors: Bonafede M. 
Published: July 2007

ABSTRACTLevelling measurements carried by Osservatorio Vesuviano over Vulcano Island (North Sicily) since June 1976 show a complex history of small but significant vertical movements which took place after the ‘Patti earthquake’ of 15/4/1978. Three phases can be identified in the time history of ground deformation: (I) co‐seismic subsidence of the northern part of the Island with respect to the southern part, followed by (II) transient inflation of the central region surrounding ‘La Fossa’ volcano, and finally (III) deflation and subsidence to stationary values greater than phase I. Large variations in temperature and gas content of magmatic origin were also detected in fumaroles along the crater rim of ‘La Fossa’. The coincidence in time of the earthquake with the start of the deformation history, the proximity of the event to Vulcano Island and the favourable mechanism (right lateral) and orientation (NNW) of the fault strike, suggest that the earthquake triggered the observed deformation. Among the plausible models, one seems particularly able to reproduce the amplitude and time evolution of the geodetic data, in a manner consistent with the geochemical observations. According to this model the earthquake, while generating a compressive stress field in the quadrant of Vulcano Island, induced at first a relative coseismic subsidence of the northern part of the island, accompanied by a large increase of the mean stress within a magma chamber at ∼ 6.5 km depth. Volatile fluids were then released from the top of the magma chamber and migrated towards the surface following the enhanced pressure gradient. As a result fluid pressure diffusion around the magma chamber induced a local transient uplift of ground that vanished after exhaustion of the overpressure at the source, and finally left a permanent dislocation deformation, possibly amplified by the post‐seismic relaxation of the earthquake deviatoric stress. This interpretation is qualitatively consistent with the one suggested by Ferri et al. (1988).
A model approach to radioactive waste disposal at Sellafield
Authors: Haszeldine R. S. , McKeown C. 
Published: July 2007

ABSTRACTOne of the great environmental problems of our age is the safe disposal of radioactive waste for geological time periods. Britain is currently investigating a potential site for underground burial of waste, near the Sellafield nuclear plant. Future leakage of radionuclides depends greatly on subsurface water flows; these must be understood from the past, to predict hydrogeology 104–105 years into the future. We have taken information from the present‐day, published by the government company Nirex, and used a finite‐element steady‐state fluid flow computer code to examine water flows in the subsurface. We find that flow directions at the planned Repository are persistently upwards, and that geologically significant flow rates could occur. How rates are particularly sensitive to uncertainties of rock permeability (conductivity) measurements made from site investigation boreholes. The hydrogeology at this site needs longer term investigation before a confident and credible prediction can be made.
Relationships between the Tertiary structural evolution of the Sardinia‐Corsica‐Provençal Domain and the Northern Apennines
Authors: Carmignani Luigi , Decandia F. Antonio , Disperati Leonardo , Fantozzi P. Lorenzo , Lazzarotto Antonio , Liotta Domenico , Oggiano Giacomo 
Published: July 2007

ABSTRACTBased on a revision of stratigraphic and structural data relative to the Balearic basin, the Corsica‐Sardinia massif, the Northern Tyrrhenian Sea and the Northern Apennines the following new hypothesis is proposed for the area located between the Sardinian‐Corsican‐Provençal and Northern Apennines regions: (a) convergence with subduction of oceanic crust under the Iberian plate beginning in the Late Cretaceous; (b) continental collision in the Oligocene‐Aquitanian, with development of the Northern Apennines belt and transpressive deformation in a hinterland that consisted of the Corsica‐Sardinia massif (still attached to the Iberian plate); (c) in the Burdigalian the tectonic regime changed from compressive to extensional. During this period the Corsica‐Sardinia massif migrated contemporaneously with opening of the Balearic basin, the Sardinian rift, and the Northern Tyrrhenian sea; (d) from the Burdigalian to the present, there was contemporaneous compression at the front and extension at the back of the Northern Apennines chain; both these features progressively migrated toward the east. The coeval extension and compression is attributed to lithospheric delamination toward the external part of the belt.
Tertiary structural relationships between Alps and Apennines: the critical Torino Hill and Monferrato area. Northwestern Italy
Authors: Piana F. , Polino R. 
Published: July 2007

ABSTRACTThe relationship between the Alpine and Apenninic orogenic systems is concealed at the surface by Tertiary sediments of two main tectono‐stratigraphic units: the ‘Alpine‐related’ Torino Hill domain and the ‘Apennines‐related’ Monferrato domain. Mapping and structural analyses carried out in the area behind the Mio‐Pliocene Apenninic‐Padane thrust front allow comparison of the kinematic history of the Torino Hill and Monferrato domains. These are separate by the transpressive Tlio Freddo Deformation Zone' (RFDZ), interpreted here as the superficial expression of a crustal discontinuity along which the Alpine metamorphic basement overrode the Apenninic Ligurian nappes during the Palaeogene.The Western Monferrato structural setting is the result of: (i) Late Oligocene‐Burdigalian transpressive tectonics due to lateral displacement between the Alps‐related and the Apennines‐related domains; and (ii) compressive post‐Messinian tectonics related to northward transport along the main Padane thrust front. Post‐Messinian tectonic events affected also the NW‐vergent asymmetrical Torino Hill anticline.
Tectonic role of ophiolite‐bearing terranes in the development of the Southern Apennines orogenic belt
Authors: Monaco Carmelo , Tortorici Luigi 
Published: July 2007

ABSTRACTNew data on ophiolite‐bearing terranes of the Liguride Complex, together with some information on the terranes of the Sicilide Complex, result in a better understanding of the role and tectonic significance of these units in the construction of the Southern Apennines orogenic belt. The Liguride Complex is composed of two main tectonic units overlain by a thick turbiditic sequence of Late Oligocene‐Middle Miocene age. The uppermost one (Frido Unit) is a polydeformed and polymetamorphosed sequence, composed of two tectonic subunits of shales and calc‐schists, respectively, containing blocks of ophiolite, garnet gneiss, amphibolites and granitoids. This unit is thrust over the un‐metamorphosed terranes (Calabro–Lucano Flysch Unit) consisting of a broken formation with blocks of Late Jurassic ophiolite and their sedimentary cover, Cretaceous‐Eocene pelagic sediments and Late Oligocene volcaniclastic deposits. The Frido Unit underwent HP/LT metamorphism (P= 8–10 Kb; T= 400–500 °C) resulting in glaucophane and lawsonite assemblages in the ophiolitic rocks and aragonite in the meta‐limestones and calc‐schists, followed by greenschist fades metamorphism (P= 4 Kb; T= 300–350 °C). From a structural point of view units of the Liguride Complex comprise structures developed at different structural levels, indicating progressive non‐coaxial deformation in response to tectonic transport towards the N‐NE. The ophiolite‐bearing terranes of the Liguride Complex can be considered as a remnant of an accretionary complex in which the Calabro Lucano Flysch Unit represents the toe of the wedge where frontal accretion processes occur and the Frido Unit is a deeper portion. Emplacement of the Frido Unit is explained as being due to formation of a deep duplex structure during the early stage of continental collision processes. The polarity of tectonic transport provides new evidence that the Liguride Complex represents a suture zone between the Apulian and the Calabrian blocks. The age of collision appears to be not older than late Oligocene. The allochtonous terranes of the Liguride and Sicilide Complexes, therefore, represent a complete accretionary wedge which records, first, subduction of the Neotethys ocean beneath the Calabrian (Europe) continental margin and, later, continental collision with the African block.
Sedimentary evolution of basins in mobile belts: examples from the Tertiary terrigenous sequences of the Peloritani Mountains (NE Sicily)
Authors: Lentini F. , Carbone S. , Catalano S. , Di Stefano A. , Gargano C. , Romeo M. , Strazzulla S. , Vinci G. 
Published: July 2007

ABSTRACTThe Tertiary covers of the Peloritani Mountain Belt (NE Sicily) provide a complete stratigraphical record of tectonic events related to collision in the Central Mediterranean region. The tectonosedimentary evolution is inferred from interpretation of new field data and indicates various stages of polyphase deformation. The Peloritani Mountain Belt is composed mostly of crystalline units representing the active margin of the European Plate that was thrust over the descending African Plate during the Tertiary. Late Eocene‐early Oligocene syn‐orogenic deposition took place within a fore‐arc basin located along the leading edge of the Peloritani Mountain Belt. From the late Oligocene to late Langhian, terrigenous deposition occurred throughout the mountain belt and extended into perched basins, located in southern areas. The basin was fed from the north, from source areas located in the hinterland of the orogenic belt. Deposition was controlled by a combination of active thrusting, regional subsidence and sea‐level change. During the early Serravallian sudden tectonic inversion took place, associated with collapse of hinterland areas and uplift of former low‐lying southern areas of the mountain belt. These processes were related to onset of opening of the Tyrrhenian Sea that was completed during the Serravallian‐Tortonian, and resulted in the deposition of a northwestward prograding clastic fan, fed by source areas located in the southern area of the mountain belt. This setting characterized Messinian and Plio‐Pleistocene deposition, and was controlled by both active tectonics and eustasy. The Recent evolution of the Peloritani Mountain Belt is characterized by major progressive uplift of the southern margins of the Tyrrhenian Basin, and local active subsidence related to downfaulting. Such processes resulted in the uplift of mid‐Pleistocene fan‐delta deposits and late Pleistocene marine terraces deposits to various altitudes above present sea‐level.
Plio‐Quaternary megasequence geometry and its tectonic controls within the Maghrebian thrust belt of south‐central Sicily
Authors: Butler Robert W.H. , Grasso Mario , Lickorish Henry 
Published: July 2007

ABSTRACTSequence stratigraphy in marine foredeep and thrust‐top basins is controlled by the conventional variations in eustatic sea‐level and sedimentation rate together with tectonics. Vertical motions reflect combinations of subsidence due to regional flexure and uplift on local thrust anticlines which act to modify the volume and shape of accommodation space together with syn‐depositional slopes. Plio‐Pleistocene successions on Sicily were deposited in thrust‐top and foredeep basins, above and ahead of evolving structures of the Maghrebian fold and thrust belt. Collectively the sediments represent a single megasequence defined at its base by a maximum flooding surface of earliest Pliocene age following reconnection with global sea‐level at the end of the Messinian. The internal stratigraphy of this megasequence consists of Trubi chalks, blue marls and a coastal calcarenite package with subordinate silciclastic sand. Plankton biostratigraphy allows these facies to be placed in a chronostratigraphic framework. Regionally the upper assemblage progrades away from the orogenic hinterland, recording a tectonically forced regression in response to regional uplift from late Pliocene times. This uplift may be associated with isostatic unloading in the orogenic hinterland due to tectonic collapse of the more internal thrust sheets. Prior to this, flexure from orogenic loading is inferred to have been sufficient for regional subsidence locally to outstrip uplift associated with the growth of some thrust structures. For shallow‐water facies the competition between thrust‐related uplift and flexural subsidence can be investigated from the stacking patterns of parasequence sets. For structures developed at greater palaeobathymetries receiving fine‐grained pelagic sediment, active tectonics may be recognized from depositional hiatuses.