bluuebunny/crossref_metadata_2025_split huggingface dataset:
Collision tectonics in the late Precambrian Eastern Ghats Mobile Belt: mesoscopic to satellite‐scale structural observations
Authors: Chetty T.R.K. , Murthy D.S.N. 
Published: July 2007

ABSTRACTRegional mapping of a section across the Eastern Ghats Mobile Belt (EGMB) north of the Godavari graben in Eastern Peninsular India by using Landsat Thematic Mapper data enables recognition of a number of shear zones, lineaments, and structural domes and basins. A conspicuous megashear occurs at the western boundary of the granulite facies rocks of the EGMB adjacent to the Archean granite‐greenstone craton. The confinement of a suite of alkaline igneous rocks to this shear zone is a notable feature. The strike extensions of this shear belt extend through to the Elchuru alkaline complex, Prakasam District, Andhra Pradesh, and the syenite plutons of Koraput district, Orissa. The contrasting lithologies, metamorphism and structural history on either side of the shear zone suggests that it might be a Precambrian suture zone.The mesoscopic structural features in the EGMB include prominent foliation with moderate to steep dips, folds, faults/shears, S‐C fabrics, pinch and swell structures and other linear fabric elements. These observations favour the consideration of drastic crustal shortening and thickening and a complex deformational sequence. The major rock units in this part of EGMB comprise garnetiferous sillimanite gneisses, quartzites and calc‐granulites forming the khondalitic suite of rocks and a wide variety of charnockitic rocks. The contact of the two rock units is generally sheared and often migmatised.The structural fabric suggests two major tectonic events: an essentially horizontal tectonic regime resulting in thrust systems and associated structures, subsequently followed by strike‐slip tectonics characterized by high shear strains. Features such as westward‐verging thrusts, large‐scale recumbent folds, major shear zones, structural domes and basins, indications of tectonic crustal shortening, extensive calc‐alkali magmatism and widespread migmatization in the region are attributed to collisional processes during Proterozoic times. The spatial disposition of the EGMB and its linkage with the distribution of similar rock units during the late Precambrian time in a global tectonic scenario are discussed.
Seismotectonics of the 20 October 1991 Uttarkashi earthquake in Garhwal, Himalaya, North India
Authors: Thakur V. C. , Kumar Sushil 
Published: July 2007

ABSTRACTThe 20 October 1991 Uttarkashi earthquake killed over a thousand people and caused extensive damage to property in the Garhwal Himalaya region. The body wave magnitude of the earthquake was 6.6, and the fault plane solution indicates reverse faulting. The hypocenrre was located at a focal depth of about 12 km between the Chail and Jutogh Thrusts, but movement propagated southward along the Jamak–Gangori Fault (JGF) and Dunda fault (DF) which are developed as blind faults related to the growing Uttarkashi antiform.
The Uttarkashi earthquake of 20 October 1991: field observations
Authors: Kumar Surendar , Mahajan A. K. 
Published: July 2007

ABSTRACTThe epicentre of the destructive 20 October 1991 earthquake is in the north‐east of the Uttarkashi region of the Higher Himalaya. The earthquake was felt up to 250–350 km away from Poh and Keylong in the north to Delhi in the south and beyond Chandigarh in the west. Seismologists of the Seismotectonic Group of Wadia Institute of Himalayan Geology studied fissures, surface breaks, and the foreshock and aftershock activity caused by this event. Land fissures show normal dislocations of 0.06–1 m, run E‐W and NE‐SW in the epicentral region and could be followed for 30–40 km.
Debate about ironstone: has solute supply been surficial weathering, hydrothermal convection, or exhalation of deep fluids?
Authors: Kimberley Michael M. 
Published: July 2007

ABSTRACTIronstone is any chemical sedimentary rock with > 15% Fe. An iron formation is a stratigraphic unit which is composed largely of ironstone. The solutes which have precipitated to become ironstone have dissolved from the Earth's surface, from the upper crust, e.g. the basaltic layer of oceanic crust, or from deeper within the Earth. Genetic modellers generally choose between surficial weathering, e.g. soil formation, and hydrothermal fluids which have convected through the upper kilometre of oceanic crust. Most genetic modellers attribute cherty laminated iron formations to hydrothermal convection and noncherty oolitic iron formations to surficial weathering. However, both types of iron formations are attributable to the exhalation of fluids from a source region too deep for convection of seawater. Evidence for a deep source of ferriferous fluids comes from a comparison of ancient ironstone with modern ferriferous sediment in coastal Venezuela. A deep‐source origin for ironstone has wide‐ranging implications for the origins of other chemical sedimentary ores, e.g. phosphorite, manganostone, bedded magnesite, sedimentary uranium ore, various karst‐filling ores, and even petroleum. Preliminary study of a modern oolitic iron deposit described herein suggests that the source of iron and silica to iron formations may have been even deeper than envisioned within most hydrothermal convection models.
Role of melt during deformation in the deep crust
Authors: Davidson Cameron , Schmid Stefan M. , Hollister Lincoln S. 
Published: July 2007

ABSTRACTDeformation in the deep crust is strongly influenced by the presence of melt. Injected melt (or magma) weakens the crust because strain will tend to localize where melt is present. The amount of strain a pluton may accommodate is dependent on the length of time it takes for a pluton to crystallize and the strain rate. For plutons that intrude into rocks which are near the solidus temperature of the melt, crystallization times can be quite long (> 1Myr).Partial melting of deep crustal rocks can lead to melt‐enhanced embrittlement. This occurs because the volume change for most melting reactions is positive. Therefore, when the rate of melt production outpaces the rate at which melt can leave the system, the melt pressure increases. Eventually, the melt pressure may become sufficiently high that the melting rocks behave in a brittle fashion and fracture.Conjugate sets of dilatant shear fractures filled with melt occur in migmatite from the Central Gneiss belt (Canada); this suggests that melt‐enhanced embrittlement occurred in these rocks. An expression which relates the magnitude of differential stress to the angle between conjugate dilatant shear fractures is derived. Assuming that migmatite has a small tensile strength, differential stresses are ≤ 20 MPa in migmatitic rocks at the time melt‐enhanced embrittlement occurs. The occurrence of melt‐enhanced embrittlement shows that a switch in deformation mechanism from plastic flow to cataclasis is possible in the deep crust during melting. Furthermore, repeated episodes of melt‐enhanced embrittlement in migmatitic rocks may be an efficient mechanism for extracting melt from partially melted terrains.
Earthquake swarm in Steigen, northern Norway: an unusual example of intraplate seismicity
Authors: Atakan Kuvvet , Lindholm Conrad D. , Havskov Jens 
Published: July 2007

ABSTRACTOn the first of January 1992, unusual earthquake activity started in Steigen, northern Norway. By 31 December, 1992, a total of 207 events had been recorded in several pulses. Among these, several events with magnitudes larger than 3.0 (Mc) were also felt by the people. The epicentral distribution of these events seems to suggest that they all are concentrated in a small region (approximately 10 km in diameter) in the Brennvika Bay (67.8°N, 14.9°E), between Leinesfjorden in the north and Nordfolda in the south. The distribution of events in time is characteristic of a swarm in which no dear evidence of a mainshock–aftershock sequence was observed. Macroseismic intensity surveys as well as synthetic modelling indicate shallow focal depths in the range 5–8 km. Based on a composite focal mechanism, indicating an oblique‐slip fault striking NE with a normal component dipping NW, combined with an observed NE trend in the epicentres and the focal depths, these events correlate with a previously proposed fault zone along Nordfolda. The NE trend has been dominant in the area throughout geological time, starting from the Caledonian Orogeny to the post‐Caledonian basin developments, as well as the post‐glacial and neotectonic structural features. At present, the deep‐seated structural anomaly underneath the Lofoten Ridge seems to be the major factor controlling the structural trends in the area. The activity along the Nordfolda fault zone could be related to this large‐scale structure, although the causes of the stresses that would create the seismic activity are not very clear, as there are several possible stress‐generating mechanisms involved, such as post‐glacial uplift of the land masses, the ‘ridge‐push’ effect from Mohn's Ridge, and vertical stresses generated by the sediment loading in the adjacent basins.
Groundwater contamination risk assessment: initial methodology for highly developed areas. Case study in the Province of Milan (Italy)
Authors: Bonomi Tullia , Cavallin Angelo , Cerutti Paolo , Rotondaro Giuseppe 
Published: July 2007

ABSTRACTMaps of factors contributing to groundwater contamination risk have been produced for a sector of the province of Milan to support decision‐making in land planning and management.Risk assessment has considered factors related to: natural vulnerability, hazard due to human activities and costs resulting from pollution. In order to evaluate existing hazard, a specific census was carried out over the area and industrial, agricultural and quarrying activities were mapped. Industrial activities were first divided into 4 groups according to national waste type regulation.The number of data and the density of mapped factors necessitated the use of a land information system for data storage and management and map design.
The youngest big impact on Earth deduced from geological and historical evidence
Authors: Kristan‐Tollmann Edith , Tollmann Alexander 
Published: July 2007

ABSTRACTThe comparison of events that followed the great impact at the Cretaceous/Tertiary boundary with those contained within the Flood myths suggests an analogous cosmic cause. This paper proposes that there is geological evidence to support this thesis which is also indicated by a careful analysis of the natural phenomena described in Flood traditions. The time, the sites, the cause, the detailed course of the events and the consequences of this catastrophe can hope to be reconstructed.
Drainage evolution in south and east England during the Pleistocene
Authors: Gibbard P.L , Allen LG. 
Published: July 2007

ABSTRACTTwo major river systems operated in southern and eastern England throughout the Pleistocene: the river Thames and the Solent river. Both rivers are axial streams of comparable size draining major basinal structures comprising similar Tertiary and Mesozoic rocks. Although the modem Thames flows broadly W‐E in the London Basin, upstream of Reading it flows from the north to drain the south Midlands. It was diverted to its present course through London by glaciation in the Anglian (Elsterian) before which it flowed across East Anglia into the southem North Sea. The Solent river no longer exists since most of its course was drowned by eustatic sea‐level rise during the Flandrian Stage (Holocene). Previously, it flowed eastwards across SE Dorset and S Hampshire as an extension of the modem river Frome in the Hampshire Basin. During periods of low sea‐level (cold stages) it was a tributary of the ‘Channel River’. Fluvial aggradations provide evidence of the former courses of these substantial rivers and their tributaries. The facies and sedimentary structures indicate that the bulk of the deposits in both systems accumulated in braided river environments under periglacial climates. Fossiliferous sediments provide biostratigraphical frameworks. During temperate periods the rivers adopted singlethread courses. Evolution of both rivers reflect their responses to climatic change, local geological structure and long‐term tectonic activity. Both rivers are undoubtedly of considerable antiquity, their records potentially extend from the Early Pleistocene or Late Pliocene, but they may have originated in the early Tertiary.
The Morphometric Synthesis for landmarks and edge‐elements in images
Authors: Bookstein Fred L. 
Published: July 2007

ABSTRACTOver the last decade, techniques from mathematical statistics, multivariate biometrics, non‐Euclidean geometry, and computer graphics have been combined in a coherent new system of tools for the biometric analysis oflandmarks, or labelled points, along with the biological images in which they are seen. Multivariate analyses of samples for all the usual scientific purposes ‐ description of mean shapes, of shape variation, and of the covariation of shape with size, group, or other causes or effects ‐ may be carried out very effectively in the tangent space to David Kendall'sshape spaceat the Procrustes average shape. For biometric interpretation of such analyses, we need a basis for the tangent space that is Procrustes‐orthonormal, and we need graphics for visualizing mean shape differences and other segments and vectors there; both of these needs are managed by the thin‐plate spline. The spline also links the biometrics of landmarks to deformation analysis of curves in the images from which the landmarks originally arose. This article reviews the principal tools of this synthesis in a typical study design involving landmarks and edge information from a microfossil.
Evolution of orthogonal sets of coeval extension joints
Authors: Caputo Riccardo 
Published: July 2007

ABSTRACTThe formation of two orthogonal sets of extension joints either crossing or abutting each other is a typical product of brittle deformation. Such systems of joints, with the two joint sets being geologically coeval, have been called a fracture grid‐lock. The two sets are of common genesis and thus a unique remote stress field can be inferred. This interpretation causes some perplexity if the two joint sets are purely extension fractures and formed perpendicular to the least principal stress. In the present paper a conceptual model to explain the origin and the evolution of such systems is proposed. In a volume of rock undergoing a tensional and uniform remote stress state, caused for example by a tectonic regime, two horizontal and negative (i.e. tensional) stress rates are assumed to exist. When the tensile strength of the rock is locally reached, failure occurs perpendicular to the least principal stress. Then, that direction locally experiences a positive stress drop due to the stress release. For this reason, the stress field, retaining the same principal directions, is locally distorted by a swap between the σ3 and the σ2 components in a volume of rock surrounding the fracture. As a consequence of the persisting remote stress rates, when elastic failure conditions are newly accumulated, a second fracture forms and propagates perpendicular to the previous one. Repeated failure events, stress‐drops and stress swaps eventually generate a fracture grid‐lock. The whole process is also described with a simplified analytical model by applying elasticity theory.
TEM observations of several spinel‐garnet assemblies: toward the rheology of the transition zone
Authors: Ingrin Jannick , Madon Michel 
Published: July 2007

ABSTRACTIn order to better identify the mineral phase which controls the rheology of the transition zone (between 410 and 660 km depth) transmission electron microscopy observations were made on several coexisting spinel‐garnet assemblies: alkremite xenolith; pyrope‐rich – MgO:1.1Al2O3 spinel assembly deformed at 1173K, 800 MPa in a Griggs apparatus; (Mg,Fe)3(Al,Mg,Si)2Si3O12 majorite – (Mg,Fe)2SiO4 spinel assembly synthesized in a laser heated diamond anvil cell. It was found that garnet crystals systematically remain undeformed while spinel crystals are plastically deformed. These results are in accord with the assumption that the rheology of majorite is stronger than the rheology of spinel, in the conditions of the transition zone.
Magnetic properties of Pleistocene sediments from the Mediterranean sea: a correlation with the palaeoclimatic record
Authors: Lanci L. , Lowrie W. , Wezel F.C. 
Published: July 2007

ABSTRACTThe magnetic properties of the late Quaternary hemipelagic sediment from piston core BS77‐15 taken in the Tyrrhenian Sea were investigated and the results compared with palaeoclimatic records. The magnetic mineralogy of the sediment was studied and the magnetic carriers were identified by their spectra of coercivity and unblocking temperature. Investigations of rock magnetic parameters such as the Natural Remanent Magnetization (NRM), the low‐field magnetic susceptibility χ, the frequency‐dependent susceptibility χfd, the acquisition of Anhysteretic Magnetization (ARM) and Isothermal Magnetization (IRM) and the Median Destructive Field (MDF) have established the downcore variations in terms of magnetic mineralogy, grain size and coercivity in the sediments. The rock magnetic parameters were compared with an alternative climatic record from the same core based on the faunal association of planktonic foraminifera. A significant correlation was found between faunal climatic record and χfd. Together with the magnetic properties of the sediment this suggests that a palaeoclimatic signal is recorded by a fine‐grained low‐coercivity fraction of the magnetic minerals.
Late Oligocene‐Miocene sedimentary evolution of the critical Alps/Apennines junction: the Monferrato area. Northwestern Italy
Authors: Clari P. , Pierre F. Dela , Novaretti A. , Timpanelli M. 
Published: July 2007

ABSTRACTThe Monferrato is a key area of the Alps‐Apennine junction. It consists of a Tertiary succession, resting on Apennine‐related units, in turn overridden by the Alpine basement. The superficial expression of this crustal discontinuity is the Rio Freddo deformation zone, separating the Alpine‐related Torino hill domain from the Monferrato. Stratigraphic analyses allow the recognition of different fault‐bounded Oligo‐Miocene successions, interpreted as tectonostratigraphic units. Some of these corresponded to high‐standing blocks, others to subsiding basins. The facies distribution reflects a transpressional tectonic regime. In this general framework of wrench tectonics, sedimentation was influenced by palaeoceanographic factors during the early and latest Burdigalian, while tectonics played the dominant role during the Aquitanian and the late Burdigalian. The uniform extent and the unconformable basal boundary of the Langhian deposits suggest that the different tectonostratigraphic units presently composing the Monferrato area were in place by Langhian times.
Tectonic history of the submerged Maghrebian Chain from the Southern Tyrrhenian Sea to the Pelagian Foreland
Authors: Catalano Raimondo , Infuso Salvina , Sulli Attilio 
Published: July 2007

ABSTRACTA description is given here of the structure and tectonic evolution of the submerged NW‐SE trending Alpine belt extending from the Sardinia Channel across the Sicily Straits to the Pelagian Sea. This mainly results from re‐interpretation of the existing seismic network. In the Sicily Straits the crust comprises an allocthonous belt composed of Tertiary flysch‐type thrust slices stacked in an imbricate wedge. The wedge is composed of Mesozoic basin and platform carbonates thrusts derived by deformation of the old Sicilian continental margin. Lower Miocene to Lower Pleistocene foredeep deposits (terrigenous and clastic carbonates) filled progressively onlapping foreland basins during regional compression. In the southern Sicily offshore the deformation spanned early Miocene to early Pleistocene time. The structural evolution of the Gela foredeep shows the kinematics and timing of emplacement of the ‘Gela Thrust System’, that is believed to be the present‐day thrust front of the Sicilian accretionary wedge. In the Sicily Channel, the Plio‐Pleistocene tectono‐sedimentary history of the Lampedusa‐Linosa sector reveals evidence of middle Pliocene extensional tectonics, and indicates a rift mechanism for formation of the Sicily Channel. This event was followed by inversion tectonics and strong vertical tectonics in the late Pleistocene.
Facies and tectonic significance of two contrasting Miocene basins in south coastal Turkey
Authors: Flecker R. , Robertson A. H. F. , Poisson A. , Müller C. 
Published: July 2007

ABSTRACTSeveral Miocene basins are developed on a mosaic of deformed Mesozoic carbonate platforms and ophiolitic units in the Antalya region of south‐west Turkey. Two of these, the Manavgat and Köprü basins, show contrasting orientations and stratigraphies. The Manavgat basin is orientated broadly SE‐NW and contains a succession of shallow‐water reef carbonates overlain by a thick sequence of deeper‐water marls. The upper part of the succession consists of sandstones, siltstones and conglomerates, mainly deposited by gravity processes. The stratigraphy of the N‐S Köprü basin can be subdivided into a western part, which consists of coarse fan delta‐conglomerates with local patch reefs, and an eastern part with thinly bedded sandy turbidites. Tooi marks indicate north to south flow in the north of the basin, but a southeasterly direction in the area of intersection with the Manavgat basin in the south‐east. In the light of alternative regional hypotheses, it is thought that early Miocene basin initiation is related to coeval southeastward thrusting of the Mesozoic Lycian Nappes. Flexural loading is inferred to have resulted in block faulting of the foreland and this exploited pre‐existing lines of structural weakness, dating from early Mesozoic rifting. mid‐Miocene relative sea‐ level rise may relate to global eustacy, and/or regional tectonic subsidence. Finally, late Miocene renewed coarse clastic input (locally very coarse) and basin infilling reflect tectonic uplift to the north, possibly related to continuing Africa‐Eurasia convergence in the region.