bluuebunny/crossref_metadata_2025_split huggingface dataset:
Geometric and kinematic coherence and scale effects in normal fault systems
Authors: Walsh John J. , Watterson Juan 
Published: April 2008

Abstract
Fault displacements derived from a seismic reflection survey of an offshore oilfield are projected onto a vertical plane parallel to the fault strike and the displacement values contoured. In addition to those for single faults, displacement diagrams are also constructed for fault arrays by aggregating the displacement values on selected faults. Displacement contours form regular and systematic patterns, even when there is no continuity between the fault surfaces in the array. A system in which linkage between the elements of a fault array is achieved by ductile strain of the intervening rock is referred to as soft-linked and is regarded as the general case. Geometrical coherence, with regular and systematic displacement patterns, exists at all stages in the growth of a fault array, implying a kinematic coherence requiring a high degree of synchronous movement, as opposed to sequential development, on individual elements in the array.
Conventional maps and diagrams allow representation of only two orders of magnitude of fault displacement rather than the five or more which may occur. A soft-domino model is presented in which the role of ductile strains is acknowledged both in accommodating varying displacements on fault surfaces and in extension on structures too small to be represented individually, and in which the rotation of rigid fault blocks is of reduced importance when compared with rigid-domino models.
Numerical and analogue modelling of normal fault geometry
Authors: Dresen G. , Gwildis U. , Kluegel Th. 
Published: April 2008

Abstract
In an attempt to constrain the influence of boundary conditions on fault nucleation and propagation processes, basement-controlled normal faulting has been simulated using analogue clay models and plane-strain finite element models. Two opposing basement configurations were investigated and the results of the analogue and numerical models were compared.
In the first series of clay models subsidence of a basement block along an inclined normal fault and along a vertical fault was simulated. An upwards-propagating fault initiated at the base of the clay model. The final fault geometry was consistent with the geometry of the stress distribution calculated in the finite element model. No listric fault developed.
In the second experiment horizontal basement extension was simulated and, as expected from the numerical calculations, these boundary conditions resulted in the formation of listric faults. The results of the analogue and numerical experiments show that initial fault geometry can be predicted successfully from the stress distribution at the elastic limit.
Calculating normal fault geometries at depth: theory and examples
Authors: White Nicky , Yielding Graham 
Published: April 2008

Abstract

In recent years, a large number of methods relating the shape of a normal fault at depth to the shape of a sedimentary horizon in its hangingwall have been described. Such methods are best used in areas where it can be assumed that the footwall remains relatively undeformed during extension. This assumption may not always be valid, especially in the case of large-scale, basement-extending normal faults. Conservation of area (or solid area when compaction occurs) must be the fundamental constraint. The advantages and disadvantages of the various methods are briefly outlined. A general model which assumes that hangingwall deforms by arbitrarily inclined simple shear and differential compaction is discussed. Fault geometry, the inclination of simple shear, and compaction parameters may all be determined from
N
beds using a simple inversion scheme based on this general method. The algorithm has previously been tested on synthetic data using a range of fault geometries. Such testing indicates that all unknown parameters including fault geometry can, in general, be uniquely determined provided that the geometries of two or more beds within the hangingwall are known. It is important that hangingwall and footwall stratigraphies are accurately known, though uncertainty in either could be included as a bounded variable within a formal inversion scheme. In this paper, the method is applied to laboratory-modelled normal faulting and to depth-converted seismic reflection data. Results suggest that hangingwalls deform by bulk, antithetically inclined, simple shear. Differential compaction of hangingwall sediments is often important and should be taken into account.
Quartz grain types in Holocene deposits from the Spanish Central System: some problems in provenance analysis
Authors: Tortosa Amparo , Palomares Marta , Arribas José 
Published: April 2008

Abstract
Holocene sands of the Spanish Central System were exclusively derived from plutonic, middle-upper grade and low-grade metamorphic rocks. Modal composition of studied sands is mostly controlled by grain size and source area lithology. Thus, sands derived from slates and schists plot near the QR edge on the QFR diagram for all grain size fractions. Sands derived from granitic or gneissic rocks have a wide dispersion on the QFR diagram, from the R pole to the QF edge, depending on sand grain size.

Percentages of quartz types in granitic-derived sands are Qnu
42
, Qu
40
, Qp2–3
14
and Qp > 3
4
. Sands of gneissic origin have Qnu
51
, Qu
15
, Qp2–3
23
and Qp > 3
11
. Sands derived from slates and schists have Qnu
20
, Qu
12
, Qp2–3
5
and Qp > 3
63
. Quartz types easily discriminate sands of low-grade origin, but distinction of sands derived from plutonic rocks from those derived from middle-upper grade metamorphic rocks is difficult because of the highly variable Qu content of plutonic rocks related to strain history and crystallization conditions. Thus, quartz types must be used with caution in source discrimination if plutonic rocks are present in the source area.
The role of fission track dating in discrimination of provenance
Authors: Hurford Anthony J. , Carter Andrew 
Published: April 2008

Abstract
Determination of single crystal ages by fission track dating analysis of zircons (and subordinately apatites) within a detrital heavy mineral assemblage, together with frequency distribution and radial plot analysis of the measured ages, permits identification of different age modes. Such modes may characterize the provenance of a sediment and assist in defining source areas. A limitation of the application is the thermal stability of tracks within a mineral above which tracks are lost and ages partially reset: in broad terms over geological time 200–250°C for zircon and <100°C for apatite. Synopses are presented of published fission track provenance studies in north central Victoria, northeastern Tasminia, Barbados, the Rockall Trough, the English Wealden, Mexico, Utah and the Central Alps.
A local source for the Ordovician Derryveeny Formation, western Ireland: implications for the Connemara Dalradian
Authors: Graham John R. , Wrafter John P. , Daly Stephen , Menuge Julian F. 
Published: April 2008

Abstract

Facies and palaeocurrent data indicate that the conglomeratic Ordovician Derryveeny Formation is the deposit of an alluvial fan whose apex was located a few kilometres east of the present outcrop. Clasts in the conglomerates include migmatite, schist, gneiss, granite, acid porphyry, spilite and vein quartz. Sillimanite bearing migmatite clasts closely resemble rocks of the neighbouring Lough Kilbride Formation, a unit of the Connemara Dalradian (Lower Proterozoic) basement from which they are presumed to be derived. This local source for the conglomerates is also suggested by the similarity of the Nd-model ages (
c.
2.15 Ga) from the metamorphic clasts and from the Lough Kilbride Formation. Moreover peraluminous granite clasts give the same model ages, suggesting the granites are intracrustal melts from the same source. Interpretation of the Connemara Dalradian as a suspect terrane requires that it docked before Upper Ordovician times. Differences between the clast assemblage in the Derryveeny Formation and the presently exposed Lough Kilbride Formation are related to stripping of the original cover, emphasizing the value of clastic detritus in the study of the uplift history of metamorphic basement.
Controls on the petrographic evolution of an active margin sedimentary sequence: the Larsen Basin, Antarctica
Authors: Pirrie Duncan 
Published: April 2008

Abstract
The sedimentary fill of the Cretaceous-Tertiary Larsen Basin, located at the northern tip of the Antarctic Peninsula, records the evolution of the Antarctic Peninsula source terrain. Uplift, and the possible renewal of arc volcanism within this area, is documented by the wide petrographic spread in the lower Gustav Group (Barremian-Coniacian). The Hidden Lake Formation (Coniacian-Santonian) records a major pulse in proximal calc-alkaline arc volcanism. The overlying Marambio Group shows a change from lithic-volcanic sandstones to quartz-feldspar-rich sandstones, reflecting a change in source terrain. An abrupt change in sandstone composition in the upper Santa Marta Formation (Campanian) may reflect both a switch in volcanism and plutonism from the east to the west coast of the Antarctic Peninsula (i.e. away from the basin margin), and a change to more mafic volcanism. The Lopez de Bertodano Formation (Campanian-Palaeocene) dominantly reflects a change to a quartzo-feldspathic source terrain (the Trinity Peninsula Group). This is also related to both a decrease in the intensity of arc volcanism and an increase in distance from the location of concurrent volcanism in relation to the site of deposition. Controls on petrography other than simple arc-unroofing (e.g. location and nature of arc volcanism and depositional setting) play an important role in sandstone petrography. These controls on sandstone composition should always be considered in interpreting sequences from active plate margin settings.
An integrated approach to provenance studies: a case example from the Upper Jurassic of the Central Graben, North Sea
Authors: Humphreys Bernard , Morton Andrew C. , Hallsworth Claire R. , Gatliff Robert W. , Riding James B. 
Published: April 2008

Abstract
The provenance of Upper Jurassic sandstones in a small half graben in the southern Central Graben of the North Sea has been investigated by studying a range of parameters: the composition of feldspars, the nature of rock fragments and their cathodoluminescence properties, heavy mineral assemblages, clay mineral assemblages, whole rock geochemistry and the occurrence of reworked palynomorphs. The combined result of these investigations is that rocks of Triassic, Permian and Carboniferous age are believed to have supplied detritus to the Upper Jurassic basin and to have diluted the contemporaneous bioclastic deposits. However, each individual provenance indicator tended to emphasize the importance of one particular source. Only an integrated study provided a complete picture of the interplay of different sources during deposition. Such integrated studies also identify the limitations of individual provenance indicators, in particular the adverse role of burial diagenesis in the removal of diagnostic grains such as volcanic feldspars and certain heavy mineral grains.
Petrographic evidence of different provenance in two alluvial fan systems (Palaeogene of the northern Tajo Basin, Spain)
Authors: Arribas José , Arribas M. Eugenia 
Published: April 2008

Abstract
Palaeogene detrital deposits of the northern Tajo Basin are coalescent alluvial fan systems interfingering distally with lacustrine carbonates. Non-carbonate extrabasinal clasts increase to the east while carbonate extrabasinal clasts decrease. Rock fragments increase to the west, while the feldspar/quartz ratio remains constant. Rock fragments define two sedimentary domains: the Iberian, in the east, was derived from Mesozoic rocks of the Iberian Range, and the Central System, to the west, was derived from Cretaceous cover and Palaeozoic metamorphic basement. Evolution of sandstone composition is related to erosion of the source areas and is different in the two domains. The tectonic setting is apparently ‘recycled orogen’, providing calcareous rock fragments are included in the total lithic clasts.
The provenance of sediments in the Barrême thrust-top basin, Haute-Provence, France
Authors: Evans Martin J. , Mange-Rajetzky Maria A. 
Published: April 2008

Abstract

This paper records the results of an integrated analysis of heavy minerals, sedimentary facies, palaeocurrents and structural data. The objective of the study was to evaluate the provenance of the sediments of the Barrême thrust-top basin. This basin contains a Late Eocene to Late Oligocene succession of shallow marine, alluvial and lacustrine sediments. Late Eocene marine transgression resulted in starvation of clastic supply to the basin hence the Calcaires Nummulitiques received only a limited influx of heavy minerals derived from local sedimentary sources, augmented by the first appearance of assemblages with andesitic affinities at
c.
42–41 Ma. Clastic members associated with the overlying Marnes Bleues record a significant diversification of provenance and sediment transport paths. Clastic detritus supplied to the shallow marine Grès de Ville were derived from Permo-Triassic sediments to the south. Conglomeratic submarine channels of the La Poste member mark the introduction of Alpine ophiolite-blueschist-derived minerals at
c.
37–35 Ma, eroded from the Embrun-Ubaya thrust complex to the NE. The deltaic St Lions member is dominated by volcaniclastic assemblages. Completing the marine fill, the shoreface Grès de Senez received detritus from the southerly Maures-Esterel crystalline massif.

The succeeding Oligocene continental sediments record an increasing supply of minerals from Alpine lithologies. The alluvial Molasse Rouge contains reworked sedimentary detritus, including material cannibalized from the underlying marine Tertiary, and first-cycle Alpine minerals. The succeeding lacustrine Série Saumon-Série Grise show the increasing diversity of Alpine suites. The youngest sediments, the fluvial Grès Verts, signal a major influx of Alpine-derived assemblages related to reactivation of the Embrun-Ubaye thrusts between
c.
28–27 and 25–24 Ma.
Evolution of the Devonian Hornelen Basin, west Norway: new constraints from petrological studies of metamorphic clasts
Authors: Cuthbert Simon J. 
Published: April 2008

Abstract
The Middle Devonian Hornelen Basin of western Norway is a continental fault-basin which formed during the late stages of the Caledonian orogeny, closely following the Late Silurian crustal thickening and high pressure metamophism responsible for the formation of eclogites in the adjacent Western Gneiss Region. Clasts from alluvial fan conglomerates which fringe the basin provide important constraints on the type of basin tectonism and the uplift history of this part of the orogen.
The clasts lack a petrographic linkage with the Western Gneiss Region (from which they are separated by a fault), but show a strong petrographic linkage with units of the allochthon (which lie unconformably below the basin fill). The clast sourceland had a similar metamorphic evolution to the allochthon, and both lack evidence for the high pressures recorded in the Western Gneiss Region. Both clasts and allochthon cooled through muscovite argon-retention temperatures about 40 Ma earlier than the Western Gneiss Region. Depth-time curves derived from isotopic and petrological results show that prior to basin initiation the Western Gneiss Region was uplifting faster than the clast source, but still lay at about 10 km depth during basin formation.
A tectonic scenario is suggested in which much of the uplift of the Western Gneiss Region took place before the deposition of the Hornelen Basin sediments, aided by crustal thinning along a major extensional mylonitic shear-zone. However, final exposure of this high-pressure metamorphic terrain only took place after the Hornelen Basin sediments were deposited, aided by uplift in the footwall of the basin sole fault.
Modern and ancient continental shelf anoxia: an overview
Authors: Tyson R. V. , Pearson T. H. 
Published: April 2008

Abstract
The characteristics of mid-latitude shelf seas are primarily controlled by seasonal cyclicity in wind-driven mixing. Seasonal dysoxic-anoxic conditions may occur in summer in salinity-stratified estuarine or pro-delta settings, or more extensively in those open shelf areas where a total depth of ≤60 m and the seasonal thermocline result in a bottom water layer ≤10 m thick. When bottom circulation is limited the oxygen stored in this layer may become periodically exhausted if climatic factors extend the stratified period to seven or more months, or if there is additional organic loading (via flagellate blooms and/or pollution). This causes widespread mortalities and a shift to soft-bodied, non-fossilizing benthic faunas. Our review supports seasonal dysoxia-anoxia as being the best model to account for the key characteristics of many ancient epeiric sea black shales. It would appear that the latter rarely represent true continuous anoxia except locally in more-confined deeper sub-basins.

We recommend that the following terms should be applied to environments, facies, or oxygenation levels: oxic (8.0–2.0 ml/l O
2
), dysoxic (2.0–0.2 ml/l), suboxic (0.2–0.0 ml/l) and anoxic (0.0 ml/l). The corresponding biofacies terms are: aerobic, dysaerobic, quasianaerobic (laminated, without macrofauna, but with in situ benthic microfauna) and anaerobic. Hypoxic and normoxic should only be used with regard to the physiological responses of living organisms.
Effects of hypoxia on continental shelf benthos: comparisons between the New York Bight and the Northern Gulf of Mexico
Authors: Boesch Donald F. , Rabalais Nancy N. 
Published: April 2008

Abstract
Depletion of dissolved oxygen to a point inducing mortality of bottom dwelling organisms (hypoxia) occurs in several continental shelf environments in Europe and North America and may have increased as a result of nutrient overenrichment due to human activities. Hypoxia in coastal waters results from plankton decomposition combined with a density stratification of the water column that hinders the oxygenation of bottom waters. Mass mortalities of benthic organisms have occurred as a result of extensive hypoxia on the inner continental shelves of the New York Bight and the northern Gulf of Mexico off Louisiana and Texas. Extensive hypoxia is rare in the New York Bight, and following catastrophic hypoxia in 1976, recovery of the benthic communities took more than two years. On the Louisiana-Texas shelf, large-scale hypoxia occurs virtually every year and recovery from this disturbance is rapid, because the community is kept in an early successional state by the annually recurring hypoxia.
A brief summary of hypoxia on the northern Gulf of Mexico continental shelf: 1985–1988
Authors: Rabalais Nancy N. , Turner R. Eugene , Wiseman William J. , Boesch Donald F. 
Published: April 2008

Abstract

Oxygen-deficient conditions occur from April to October on the inner to middle continental shelf of the northern Gulf of Mexico and may cover up to 9500 km
2
during mid-summer off the Louisiana coast. Hypoxic bottom waters are found in 5–60 m water depth, 5–60 km offshore and extend up to 20 m above the bottom. Salient forcing functions contributing to hypoxic water formation, maintenance and break-up are presented. Stratification is directly correlated with hypoxia in time and space, suggesting that reaeration of bottom waters is controlled by physical processes that are influenced by regional wind fields, river discharge and continental shelf scale currents. Phytoplankton biomass reaches the bottom waters in the hypoxic zones in large amounts (>5 µg/l), fueling water column and benthic respiration rates, but to a currently unknown degree. Increased nutrient loadings in the two major rivers and changes in the proportion of those nutrients essential to phytoplankton growth have probably changed both the phytoplankton community species composition and community production. It is not yet clear whether the extent and severity of hypoxia on the Louisiana continental shelf have changed as a result of these riverine water quality changes.
Recovery responses of two benthic assemblages following an acute hypoxic event on the Texas continental shelf, northwestern Gulf of Mexico
Authors: Harper Donald E. , McKinney Larry D. , Nance James M. , Salzer Robert R. 
Published: April 2008

Abstract
A hypoxic/anoxic event occurred in the northwestern Gulf of Mexico between May and July 1979. This event, associated with warm water temperatures, water column stratification and the decay of a phytoplankton bloom, led to the production of hydrogen sulphide which moved above the sediment—water interface and into the lower 2 metres of the water column. Regular monthly sampling at two sites (15 and 21 m depths) off Freeport, Texas, showed that abundances of benthic organisms declined precipitously during the event. Divers inspecting the study areas during the event observed ‘cottony’ mats, presumed to be sulphur bacteria colonies, covering large areas of bottom, and numerous bodies of dead benthic invertebrates.
Recovery of the two communities was markedly different. The assemblage in deeper water apparently stabilized within a year; the species of polychaetous annelids that were dominant before the event quickly returned to dominance and there was very little evidence of succession of different species during the recovery process. The shallower water assemblage, however, underwent a very different recovery process. Following the hypoxic event, polychaete dominance was greatly reduced, and there occurred successional dominance which involved several species in different taxa. Each of these species underwent a ‘bloom’ and constituted the numerical dominant for 1 to 3 months, and then declined and was replaced by another species’ ‘bloom’. This sequential dominance pattern persisted until about May 1981, two years after the hypoxic event, at which time polychates again became, and remained, numerically dominant.
Biofacial patterns in river-induced shelf anoxia
Authors: Van Der Zwaan G. J. , Jorissen F. J. 
Published: April 2008

Abstract
Three areas were studied to assess the effects of riverine input on the marine benthic ecosystem: the Adriatic Sea (with the Po river), the Orinoco-Paria shelf (with the Orinoco and Essequibo rivers) and the northern Gulf of Mexico (with the Mississippi and Rio Grande rivers). In all these areas, the interplay of river-discharge and subsequent transport by surface-water currents has resulted in the deposition of a zone with finegrained, organic-rich sediments parallel to the coast. The foraminiferal associations occupying these mud-belts indicate the occurrence of regular, widespread anoxic or dysoxic conditions at the sediment-water interface. Across the mud belt, benthic foraminifera display a very characteristic zonation, which is essentially the same in all areas studied. In the centre of the zone, low diversity and the presence of opportunistic species indicate a degree of stress. A model which describes the microhabitat occupation within these muddy zones is discussed in some detail. We conclude that the width of the shelf, together with the force of the long-shore current carrying the riverine products into the basin, are essential in determining the occurrence of dysoxic or anoxic conditions while the discharge volume of rivers is a subordinate factor. The chance of anoxia appears to be highest during periods of high sea level, leading to large shelf areas. A final conclusion is that benthic formainifera are excellent tools for determining the occurrence and degree of marine eutrophication induced by the input of polluted river waters.