bluuebunny/crossref_metadata_2025 huggingface dataset:
Quaternary evolution of a meandering gravel bed river in central Spain
Authors: Alonso A. , Garzón G.
Published: July 2007

The river Jarama is a medium‐sinuosity meandering river with gravel bedload. Throughout the Quaternary it developed a large number of terraces in a repetitive sequence of aggradation‐stability‐degradation‐stability stages, which are studied in the middle reach of the river, applying geomorphological and sedimentological methods, as well as kadiocarbon dating techniques. The Upper Terrace System of earliest Pleistocene to mid Pleistocene age forms isolated fragments vertically disconnected and colluviated, and their sequential distribution of facies implies lateral shifting of channels and a welldeveloped flood plain. The Middle Terrace System of mid‐to‐late Pleistocene age has differentiated levels in the upstream reaches while downstream they condense giving a thick multi‐episodic series, corresponding to the tectonic tilting of the basin. Classical point bar fining‐upward sequences of a medium‐ to high‐sinuosity river (with gravels and sands as bedload) are clearly differentiated in them. A major degradation stage follows this group of terraces, with an incision of up to 30 m. Then, during a relatively long period of stability, a forest of riparian species developed, prior to the last aggradational stage of the Lower Terrace System. The aggradation resulted in a fining‐upward sequence where lateral accretion is clearly visible in the gravels, due to migration of the medium‐ to low‐sinuosity river. Sedimentation continued and was active up to the 1950s, but since then, intense anthropogenic modifications led to renewed incision of the river.
Climate‐related river activity at the Weichselian‐Holocene transition: a comparative study of the Warta and Maas rivers
Authors: Vandenberghe J. , Kasse C. , Bohncke S. , Kozarski S.
Published: July 2007

Huvial systems from the Dutch and Polish lowlands are compared for their evolution during the Weichselian deglaciation period. In both regions the Pleniglacial braided‐river pattern changed to a meandering pattern in the beginning of the Lateglacial. Several transitional stages between braided and high‐sinuosity meandering systems have been recognized. A difference in fluvial activity is found during the Younger Dryas when the Maas transformed to a braided pattern while the Warta maintained its meandering pattern. Phases of erosion and aggradation are more or less synchronous in the different river basins, but their intensity may differ greatly. The major characteristics of the fluvial systems are obviously a response to the general climatic evolution and related to changes in vegetation. The regional differences are of minor importance and can be explained by site‐specific factors. Threshold values within the latter factors define the changes in river dynamics.
Reflection of the glacial‐interglacial cycle in the evolution of the Vistula river Basin, Poland
Authors: Starkel Leszek
Published: July 2007

A variety of factors has controlled the evolution of the Vistula river valley. They include climatically induced changes of the river runoff and sediment load, glacial advances and rapid variations of the base level, as well as the influence of the tectonic factor. The first‐order climatic cycles are reflected in separate terrace fills. The second‐order fluctuations may be represented by separate cuts and fills, by the change of the facies or by the change in the granulometric composition. The analysis of the changes in the longitudinal profile helped to discover a great variety of different valley reaches and a general tendency to smooth the long profile during the Quaternary.
Pleistocene evolution of the Danube in the Carpathian Basin
Authors: Gábris Gyula
Published: July 2007

The present‐day drainage system of the Carpathian Basin originates from the gradual regression of the last marine transgression (brackish Pannonian Sea). The flow directions of the rivers including the Danube, are determined by the varying rates and locations of subsidence within the region. The Danube, which forms the main axis of the drainage network, first filled the depression of the Little Plain Lake and then, further southward, the Slavonian Lake. From the end of the Pliocene, the crustal movements which caused the uplift of the Transdanubian Mountains, forced the Danube to flow in an easterly direction, towards the antecedent Visegrid Gorge, and into the subsiding basins of the Great Plain. Climatic changes during the Pleistocene had the effect of forming up to seven fluvial terraces. The uplift of the mountains is demonstrated by the deformation of the terraces, while the subsidence of the Plains is proven by an accumulation of several hundred metres of sediment. The river only occupied its present position south of Budapest in the latest Pleistocene.
Morphology and post‐Chaudian (Late Pleistocene) evolution of the submarine Danube fan complex
Authors: Wong H.K. , Panin N. , Dinu C. , Georgescu P. , Rahn C.
Published: July 2007

The Danube deep sea fan in the northwestem Black Sea has a lateral dimension of over 150 km and stretches from several hundred metres water depth down to the abyssal plain. Eight seismic sequences have been recognized in the fan complex. Each sequence consists of channel, levee and overbank deposits, as well as mass transport units. The Danube and the Ukrainian rivers have aggraded two surficial channel‐levee systems which diverge and decrease in volume downfan. The channels of these systems have a low sinuosity, implying young age, steep gradients and/or limited sediment supply. Significant channel migration occurred in the course of fan development, which could be largely controlled by relative sea‐level changes. The six youngest sequences mapped have been correlated to sea‐level fluctuations from the post‐Chaudian regression to the present day.
Imaging of the Moho depth in Madagascar through the inversion of gravity data: geodynamic implications
Authors: Fourno Jean‐Pierre , Roussel Jacques
Published: July 2007

Several E‐W profiles of Bouguer anomalies across the Precambrian basement were inverted by applying a linearized inversion procedure in the spectral domain and using a simplified two‐layer model with a crust‐upper mantle interface of constant density contrast. From these inverted profiles, a contour map of Moho topography has been constructed which covers the area of exposed Precambrian basement in the eastern and central parts of the island. Such imaging of the Moho depth in particular exhibits a N20°E‐trending zone of substantially thinned crust along the axis of the island. This parallels the east coast margin which resulted from the northward motion of India relative to Madagascar in the Upper Cretaceous. From combined analysis of geological, tectonic and metamorphic observations, this prominent crustal feature in the Precambrian basement of Madagascar is interpreted as the relic of continental lithospheric extension and thinning possibly related to Panafrican collapse tectonics on the eastern edge of the Mozambique belt. This extensional feature would have been reactivated only in part during the rifting and dislocation stages of the Madagascar and India continental blocks as evidenced by an axis of Cretaceous volcanism emphasized by the Ankaratra and Itasy massifs. Final separation nevertheless occurred further east, at the site of the east coast margin.
Neogene carbonate stratigraphy of Ontong Java Plateau (Western Equatorial Pacific): three unexpected findings
Authors: Berger W.H. , Stax R.
Published: July 2007

The Neogene carbonate stratigraphy of five sites drilled on Ontong Java Plateau during Leg 130 reveals a number of patterns which are unexpected, and which we refer to as loss paradox, equatorial insensitivity, and climate paradox. They denote the following unresolved questions.

The loss of carbonate at depth (as derived from differences in accumulation rates) is much greater than suggested by the change in carbonate percentages (calculated under the assumption that carbonate dissolution is the cause of loss). This indicates an important role for redeposition processes, such as winnowing (bottom currents), sifting (resuspension and catabatic flow) and episodic sloughing or solifluction (presumably stimulated by earthquakes).

Accumulation rates are not markedly increased at the time a site crosses the equator. There are several possible reasons. Equatorial upwelling may be unimportant in controlling sedimentation rates this far in the western Pacific, or its output may be spread over a considerable distance from the equator. Alternatively, increased supply below the equator is compensated for by increased removal (e.g. from resuspension by bioturbation, combined with catabatic flow). It is conceivable that errors in the timescale could also produce the effect seen.

There is an overall tendency for agreement between the stratigraphic patterns of carbonate content and of accumulation rates, but neither pattern is readily explained by reference to changes in climate (represented by benthic δ18O) or in sea‐level (as derived from sequence stratigraphy).
Local displacement rate cycles in the life of a fold‐thrust belt
Authors: Butler Robert W.H. , Bowler Sue
Published: July 2007

The evolution of minor structures during the growth of major folds and thrusts, in the Chartreuse district of the French Subalpine thrust belt, shows that each thrust evolved through a phase of distributed faulting, major thrust propagation and displacement, followed by distributed shear modification of the hanging‐wall fold. Microstructural studies suggest that the distributed faulting phases, early and late in the history, were characterized by strain rates limited by diffusive mass transfer processes (c. 10‐15‐10‐16 s‐1). Faulting whose rate is limited by DMT is too slow on its own to accommodate the regional time‐averaged shortening rates for the thrust belt as a whole, implying that the slow thrusts operated in tandem with those major, fast thrusts where deformation was primarily cataclastic. Consequently each thrust anticline experienced a displacement rate cycle and an array of thrust anticlines must amplify simultaneously. These interpretations raise important issues for the dynamics of fault populations, the evolution of thrust wedges and the history of fluid migration in thrust belts.
The Kolmogorov model of bed‐thickness distribution: an assessment based on numerical simulation and field‐data analysis
Authors: Muto Tetsuji
Published: July 2007

Kolmogorov's model of the distribution of bed thicknesses is assessed by numerical simulations of a sedimentation process, assumed to be a random time‐series of alternating depositional and erosional episodes conformable with a stationary Markov process in a state of equilibrium. The study supports the validity of the main point of the model. The random time‐series process generates a succession of beds with ‘positive’ (preserved) and ‘negative’ (eroded) thicknesses, the frequency distribution of which, f(x), spans the range of positive to negative x‐values. The beds with negative thicknesses are absent in the stratigraphic record, whereby the measured bed thicknesses show a frequency distribution, f*(x | x > 0), that is left‐side truncated, cut off at the zero thickness value. The numerical simulations further indicate that f(x) is a ‘composite’ geometrical distribution, whose actual form changes progressively with pd, the probability of sediment deposition relative to erosion. The distribution f(x) invariably has a maximum at x≤0, such that the truncated distribution f*(x) for pd≥0.5 is a simple geometrical distribution regardless of pd value. The f*(x) distribution will appear to be a negative exponential distribution when based on the bed‐thickness data measured in a conventional metric scale. Data sets from four different turbidite successions in the Cenozoic of Japan, each comprising a few thousand beds, show this type of distribution. However, the sandstone‐capping shales in one of the turbidite successions show a truncated Gaussian distribution, attributed to a significant component of non‐turbiditic mud. No universal form of bed‐thickness distribution can be assumed for the Kolmogorov model. The form of bed‐thickness distribution may vary with the type of the depositional process and the character of the sedimentary environment.
When did Sardinia stop rotating? New palaeomagnetic results
Authors: Vigliotti L. , Langenheim V.E.
Published: July 2007

Previous palaeomagnetic results from Tertiary volcanic rocks of Sardinia suggest that the island underwent a quick counterclockwise rotation between 20.5 and 19 Ma. In order to test this hypothesis, a new palaeomagnetic study was carried out on sediments and volcanic rocks with well‐controlled biostratigraphic or radiometric ages younger than the suggested age for the end of the rotation.

Unrotated palaeomagnetic directions obtained from the Upper Ignimbrites (radiometric age: 18.5–19.7 Myr) and the Aquitanian tuffs collected in the Anglona region (N Sardinia) would suggest that the rotation ended earlier than 20.5 Myr. The directions found in the volcanics are perhaps the result of secular variation, rather than differential rotation of the Anglona region with respect to surrounding regions.

Two sites belonging to the upper ignimbritic unit (SI2) in the Monte Traessu‐Monte Rispisu area (Logudoro region) exhibited a large amount of rotation (D=320.4°, I=60°) which may be age related (radiometric age: 19.9 Myr). Four dikes (radiometric age: 18.3–16.7 Myr) in the Arcuentu volcanic complex (Arburese region) yield results (D=348.4°, I=33.8°) that indicate a further amount of rotation after their emplacement.

Stable end‐point directions were successfully isolated from three Upper Burdigalian/Langhian sedimentary sites (biostratigraphic age: 18–15Ma) from the Marmilla and Logudoro regions. Consistent paleomagnetic directions obtained from these sites (D=352°, I=49°) indicate that a small amount of rotation was still to be completed in the Langhian time. This result is consistent with the history of Sardinian volcanism, which did not end until 13 Ma.
Oblique rifting in Salina, Lipari and Vulcano islands (Aeolian islands, southern Italy)
Authors: Mazzuoli Roberto , Tortorici Luigi , Ventura Guido
Published: July 2007

A structural analysis carried out on the volcanic products of the islands of Salina, Lipari and Vulcano (Aeolian archipelago) points out that the large‐scale tectonic setting is dominated by NW‐SE trending right‐lateral extensional strike‐slip faults and by N‐S to NE‐SW trending normal faults and fractures. This fault pattern generates pull‐apart type structures, developing between different right‐hand overlapping fault segments and a characteristic extensional imbricate fan geometry at the tip of the major strike‐slip faults. All the structures, representing the surface expression of an active crustal discontinuity which controls the evolutionary history of the magmatism of the three islands, are kinematically compatible with a N100°E extension related to a rifting process affecting southern Italy.
Fluid venting from a mud volcano in the Mediterranean Ridge Diapiric Belt
Authors: Cita M.B. , Woodside J.M. , Ivanov M.K. , Kidd R.B. , Limonov A.F. ,   Scientific Staff of Cruise TTR3 ‐ Leg 2
Published: July 2007

Direct observation of active emission of fluids and mud from a submarine mud volcano were made for the first time in an extensive field of mud diapirs and mud volcanoes on the Mediterranean Ridge using a video camera towed 2 m above the seafloor in 1800 m of water. This recent research using both long range and deep‐towed sidescan sonar systems indicates also that diapirism and eruption of mud along the crest of the ridge is more common than previously thought. The southwards increase in age of rock fragments carried within the erupted mud supports the hypothesis that the fluid mud becomes overpressured within a southward‐dipping backthrust from the Inner Deformation Front of this accretionary prism.
Representation of normal slant faults in a 2D burial history model
Authors: Lerche I. , Yu Z. , Liu J.
Published: July 2007

A discussion is given of the impact of normal slant faults on basinal structure, compaction, fluid overpressure development, and thermal effects in sedimentary basins. Faults which are hydraulically closed or open to fluid flow are examined in a dynamical two‐dimensional fluid/ flow compaction model.

From this numerical investigation three dominant factors characterize the effects of single and multiple faults with open or closed hydraulic behaviours: (i) there is a difference in excess pressure for fault planes with open or shut hydraulic conditions, but the neighbourhood where the effect of the fault is dominant is fairly localized (to within about half a kilometre or so laterally from the fault plane); (ii) the lateral and vertical motion of sediments between faulted blocks induces a thermal difference prior to, during, and post‐faulting, which can play a role in influencing hydrocarbon generation, migration, and accumulation; (iii) porosity retention and permeability modification by fault development could influence hydrocarbon exploration decisions regarding sealing, migration pathways, and fluid retention.

The general patterns of slant fault effects described here should prevail in most geological situations, because the numerical experiments are designed to illuminate sharply the dominant response characteristics within the framework of simplified situations.
Sr isotope evolution of Maastrichtian seawater, determined from the chalk of Hemmoor, NW Germany
Authors: McLaughlin Ó.M. , McArthur J.M. , Thirlwall M.F. , Howarth R. , Burnett J. , Gale A.S. , Kennedy W.J.
Published: July 2007

In 140 metres of Maastrichtian White Chalk (nannofossil chalk) exposed near Hemmoor, NW Germany, values of 87Sr/86Sr increase from 0.707760 in the Belemnella sumensis Zone (Lower Maastrichtian) at the base of the section (‐54.5 m; referred to 0 m at a prominent marl, M900) to 0.707821 in the Belemnella baltica/danica Zone (Upper Maastrichtian) at the top of the section (+84.5 m). A plateau in 87Sr/86Sr occurs between ‐5m and +50m in the section, probably as a result of a very high rate of sedimentation in this interval. A belemnite and associated nannofossil chalk have similar 87Sr/86Sr values, suggesting that there has been little diagenetic alteration of the 87Sr/86Sr ratios in the chalk, which therefore preserves its original 87Sr/86Sr. Comparison of 87Sr/86Sr and nannofossil zonations for sequences at Bidart, France, and DSDP Sites reveals discordance and so possible diachronism of the basal boundaries of nannofossil Zones CC25B and CC25C.
A new indicator of movement direction during orogenesis: measurement technique and application to the Alps
Authors: Bell T.H. , Forde A. , Wang J.
Published: July 2007

The orientation of axes of sigmoidal, staircase or spiral inclusion trails within porphyroblasts provides an indicator of the direction of movement during deformation that is synchronous with metamorphism. A simple technique is presented in detail to find this axis in 3D by radially sectioning a horizontal slab cut from an oriented sample. When viewed from one direction, the switch in asymmetry of the porphyroblast inclusion trails in these sections defines the trend of the axis. Further radial sectioning of a vertical slab cut parallel to this trend determines the plunge of this axis.

This technique is independent of the model adopted for the formation of sigmoidal or spiral‐shaped inclusion trails and can be used to evaluate the mechanism by which they form. It can also be used to evaluate theories of folding and orogenesis. Measurements of spiral and sigmoid axes in garnet porphyroblasts from the European Alps show that they reflect the movement of the African Plate relative to Europe better than linear indicators preserved within the same rocks.
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

A 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

Resolution 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

The 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

In 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

Recent 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

The 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

Because 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

Levelling 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

One 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

Based 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

The 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

New 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

The 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

Sequence 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.
Cretaceous to Neogene structural evolution of the Lampedusa Shelf (Pelagian Sea, Central Mediterranean)
Authors: Torelli Luigi , Grasso Mario , Mazzoldi Glauco , Peis Davide , Gori Davide
Published: July 2007

Studies of multichannel seismic reflection profiles, calibrated with borehole data, have been carried out in the Tunisian shelf surrounding the islands of Lampione and Lampedusa, in order to define the Mesozoic‐Cenozoic stratigraphie and structural evolution of this sector of the Pelagian foreland. The stratigraphy and subsidence history show a subsiding Upper Jurassic carbonate platform buried, by syn‐ and post‐rift neritic to deep marine siliciclastics, marls and limestones of Neocomian‐early Eocene age. Thick Middle‐Upper Eocene shallow‐water carbonates (Halk el Menzel Fm.), lie unconformably over the deep‐water sediments and exhibit progradational geometries.

Messinian evaporites are confined to the deepest parts of the Neogene basins and Plio‐Quaternary sediments are widespread over the area. Several unconformities affect the stratigraphic column and have been interpreted as related to compressive events during Late Cretaceous‐early Tertiary times. These compressive events produced uplift, folding and reverse faulting, trending about NW‐SE and partly reactivating Lower Cretaceous extensional structures. The uppermost regional unconformity indicates widespread emergence and erosion during Oligocene and Miocene tintes and was probably related to a younger compressional phase. A strong Upper Miocene‐Quaternary extension event also affected the area, characterized by WNW‐ESE trending normal faults, parallel to faults flanking the main grabens of the Sicily Strait rift zone. Since the Messinian, the structural evolution of the area has been controlled by rift‐related processes which triggered crustal extension in the Pelagian foreland.
Study of the Messinian carbonate‐evaporite lithofacies offshore Western Libya
Authors: Mriheel Ibrahim Y. , Alhnaish Abdelhakim S.
Published: July 2007

This study represents a preliminary investigation of the late Messinian subsurface Marsa Zouaghah Formation in the Western Libyan Offshore, Central Mediterranean Sea. The formation was deposited in three major environmental settings: (a) Marginal Sabkha; (b) Open Lagoon; and (c) Hypersaline Lagoon. The marginal sabkha and open lagoonal settings are locally interrupted by intertidal oolitic shoal deposits. The marginal sabkha facies is replaced in central parts of the Libyan offshore by a narrow zone of aeolian‐fluvial facies, the distribution and thickness of which is entirely controlled by a local uplift, the Tripoli Nose'. The marginal sabkha facies broadly defines the late Messinian palaeoshoreline lying parallel to, and north of, the E‐W Jifarah fault system which dominated the southern part of the Libyan offshore. This fades is, thus, interpreted as being structurally controlled by fault systems. The hypersaline lagoonal facies is developed in areas of relatively higher rates of subsidence than that of adjacent facies belts. It is therefore, related to restriction formed by continuous subsidence and evaporation. The Marsa Zouaghah Formation constitutes saltern evaporates deposited over a wide platform in sabkha and lagoonal settings, forming part of the ‘basin‐wide‐evaporites’ of the Mediterranean Basin deposited during the Messinian salinity crisis. The evaporites formed during a major relative sea‐level fall within a subsiding basin situated on the northern continental margin of the African plate. Local, vertical and lateral variations in lithofacies and thickness within the Messinian deposits of the north‐west Libyan offshore were controlled by contemporaneous strike‐slip movements in addition to sea‐level change.
Hydrothermal sedimentation in the caldera of Santorini, Hellenic Volcanic Arc
Authors: Cronan D.S. , Varnavas S. , Perissoratis C.
Published: July 2007

Sediments in the caldera of Santorini are receiving a hydrothermal input of iron and manganese from presently active hydrothermal vents off the Kameni Islands, and are enriched in these elements in their surface layer. However, greater Fe‐Mn enrichments occur in discrete layers at depth in the cores separated from the surface by Fe‐Mn poor sediments, suggesting that a past hydrothermal event may have been more intense than the present one. The buried Fe‐Mn enriched layers occur above a turbidite thought to have resulted from sediment slumping due to a major volcanic eruption and earthquake in 1650, and are thought to have formed consequent on the activation of faults related to the magma chamber by the eruption facilitating seawater‐rock interaction processes and the formation of metal‐rich hydrothermal solutions.
Ocean's philosophical images
Authors: Givone Sergio
Published: July 2007

From early Greek cosmology and pre‐socratic thought to Kant, Nietzsche and the philosophy of existence, ‘ocean’ is a figure of the most relevant significance, in accordance with two different patterns: as mythical representation of the principle of the universe and as metaphor of the adventure of human knowledge. Now the question could be: do the philosophical images of the ocean have some value for modern science?