bluuebunny/crossref_metadata_2025 huggingface dataset:
Cognitive Recovery in Socially Deprived Young Children: The Bucharest Early Intervention Project
Authors: Nelson Charles A. , Zeanah Charles H. , Fox Nathan A. , Marshall Peter J. , Smyke Anna T. , Guthrie Donald
Published: December 2007

In a randomized controlled trial, we compared abandoned children reared in institutions to abandoned children placed in institutions but then moved to foster care. Young children living in institutions were randomly assigned to continued institutional care or to placement in foster care, and their cognitive development was tracked through 54 months of age. The cognitive outcome of children who remained in the institution was markedly below that of never-institutionalized children and children taken out of the institution and placed into foster care. The improved cognitive outcomes we observed at 42 and 54 months were most marked for the youngest children placed in foster care. These results point to the negative sequelae of early institutionalization, suggest a possible sensitive period in cognitive development, and underscore the advantages of family placements for young abandoned children.
Coupled
142
Nd-
143
Nd Isotopic Evidence for Hadean Mantle Dynamics
Authors: Bennett Vickie C. , Brandon Alan D. , Nutman Allen P.
Published: December 2007

The oldest rocks—3.85 billion years old—from southwest Greenland have coupled neodymium-142 excesses (from decay of now-extinct samarium-146; half-life, 103 million years) and neodymium-143 excesses (from decay of samarium-147; half-life, 106 billion years), relative to chondritic meteorites, that directly date the formation of chemically distinct silicate reservoirs in the first 30 million to 75 million years of Earth history. The differences in
142
Nd signatures of coeval rocks from the two most extensive crustal relicts more than 3.6 billion years old, in Western Australia and southwest Greenland, reveal early-formed large-scale chemical heterogeneities in Earth's mantle that persisted for at least the first billion years of Earth history. Temporal variations in
142
Nd signatures track the subsequent incomplete remixing of very-early-formed mantle chemical domains.
Structure of Gα
q
-p63RhoGEF-RhoA Complex Reveals a Pathway for the Activation of RhoA by GPCRs
Authors: Lutz Susanne , Shankaranarayanan Aruna , Coco Cassandra , Ridilla Marc , Nance Mark R. , Vettel Christiane , Baltus Doris , Evelyn Chris R. , Neubig Richard R. , Wieland Thomas , Tesmer John J. G.
Published: December 2007

The guanine nucleotide exchange factor p63RhoGEF is an effector of the heterotrimeric guanine nucleotide–binding protein (G protein) Gα
q
and thereby links Gα
q
-coupled receptors (GPCRs) to the activation of the small-molecular-weight G protein RhoA. We determined the crystal structure of the Gα
q
-p63RhoGEF-RhoA complex, detailing the interactions of Gα
q
with the Dbl and pleckstrin homology (DH and PH) domains of p63RhoGEF. These interactions involve the effector-binding site and the C-terminal region of Gα
q
and appear to relieve autoinhibition of the catalytic DH domain by the PH domain. Trio, Duet, and p63RhoGEF are shown to constitute a family of Gα
q
effectors that appear to activate RhoA both in vitro and in intact cells. We propose that this structure represents the crux of an ancient signal transduction pathway that is expected to be important in an array of physiological processes.
Structural Rearrangements That Govern Flow in Colloidal Glasses
Authors: Schall Peter , Weitz David A. , Spaepen Frans
Published: December 2007

Structural rearrangements are an essential property of atomic and molecular glasses; they are critical in controlling resistance to flow and are central to the evolution of many properties of glasses, such as their heat capacity and dielectric constant. Despite their importance, these rearrangements cannot directly be visualized in atomic glasses. We used a colloidal glass to obtain direct three-dimensional images of thermally induced structural rearrangements in the presence of an applied shear. We identified localized irreversible shear transformation zones and determined their formation energy and topology. A transformation favored successive ones in its vicinity. Using continuum models, we elucidated the interplay between applied strain and thermal fluctuations that governs the formation of these zones in both colloidal and molecular glasses.
Can cause of death be predicted from the pre-necropsy information provided in coroners’ cases?
Authors: Biggs M J P , Brown L J R , Rutty G N
Published: December 2007

Aim:

To determine whether the cause of death can be accurately predicted from the pre-necropsy information available in coroners’ cases, before carrying out a postmortem examination.

Methods:

In this prospective study pathologists read the clinical summary provided by the Coroner’s Office and formulated a predicted cause of death. An external examination was then conducted and any relevant information recorded, together with any changes to the original predicted cause of death. They then carried out a complete necropsy before recording a final cause of death, which was subsequently compared with their prediction.

Results:

A total of 95 necropsies were included in the study. The cause of death was deemed to have been correctly predicted from the history in 62 cases (65.3%). In 33 cases (34.7%) an unexpected cause of death was found. Findings from the external examination were noteworthy in only 8 cases (8.4%), and did not alter the cause of death in any case.

Conclusions:

In certain circumstances an accurate cause of death may be given with confidence without the apparent need for necropsy. However, many common causes of death can present with similar or misleading scenarios. This study indicates that performing necropsies, despite seemingly predictable circumstances, is advisable if an accurate cause of death is to be recorded.
Debating disability
Authors: Shakespeare T
Published: December 2007

This paper responds to the reviews by Edwards, Holm, Koch, Thomas and Vehmas ofDisability Rights and Wrongs(2006). After summarising the recent history of disability studies as a discipline, it explores: the political nature of disability research, questions of ontology and definition, and the uses and abuses of the expressivist argument. Disability is an emerging field of enquiry and constructive debate is to be welcomed.
Estimating reduction in occupational disease burden following reduction in exposure
Authors: Armstrong B G , Darnton A
Published: December 2007

Background/objective:

Many occupational exposures causing disease cannot feasibly be eliminated entirely, but policies that reduce the exposures may be under consideration. This paper sets out to clarify how to estimate the reduction in occupational disease following a reduction in exposure, and shows a real-data illustration for doing this.

Methods:

Modest extensions of standard expressions for attributable fractions permit estimation of fractions by which cases would be reduced by policies that do not eliminate exposure but change exposure distributions. However, this requires information on the exposure-response relation and on distribution of exposures.

Results:

From hypothetical scenarios and a real example this paper explores how attributable cases are distributed by exposure level and, in particular, the proportion by which attributable cancers are reduced by eliminating exposures above a limit (the classic occupational limit regulation). It shows how this depends on the shape of the exposure-response relation and to some extent the shape of the exposure distribution, as well as on the proportion exposed above the limit. For linear no-threshold relations and left-skewed exposure distributions, the majority of the burden may be in a large number of people experiencing small relative risks, and thus may not be tackled by a strategy to reduce exposures above a certain limit.

Conclusion:

With appropriate data, estimating the disease burden in terms of the distribution of exposure is straightforward and can help to clarify the likely outcome of an intervention.
A NONLINEAR UNSTEADY RESPONSE OF NON-NEWTONIAN BLOOD FLOW PAST AN OVERLAPPING ARTERIAL CONSTRICTION
Authors: SEN S. , CHAKRAVARTY S.
Published: December 2007

The present study deals with an appropriate mathematical model describing blood flow through a constricted artery that is used to analyze the physiological flow field. The time-variant geometry of the arterial segment having an overlapping type of constriction in the arterial lumen — which frequently occurs in diseased arteries, causing flow disorder and leading to malfunction of the cardiovascular system — is framed mathematically. Blood flow contained in the stenosed artery is treated as non-Newtonian (having shear-dependent viscosity) and is considered to be two-dimensional. The motion of the arterial wall and its effect on local fluid mechanics are not ruled out from the present pursuit. The flow analysis applies the time-dependent, two-dimensional incompressible nonlinear Navier–Stokes equations for non-Newtonian fluids. The flow field can be obtained by first transforming radial coordinates with the use of appropriate boundary conditions, and then adopting a suitable finite difference scheme numerically. The unsteady response of the system and the influence of the arterial wall distensibility, the non-Newtonian rheology of blood, and the presence of stenosis on the important aspects of the physiological flow phenomena are quantified in order to indicate the susceptibility to atherosclerotic lesions and thereby validate the applicability of the present theoretical model.
Progressive unconformities within an evolving foreland fold–thrust belt, Zagros Mountains
Authors: HESSAMI KHALED , KOYI HEMIN A. , TALBOT CHRISTOPHER J. , TABASI HADI , SHABANIAN ESMAEL
Published: December 2007

A major angular unconformity between the Bakhtyari conglomerates and the underlying Agha Jari Formation has long been interpreted as indicating that orogeny in the Zagros Simply Folded Zone took place in Plio-Pleistocene times. This study uses field evidence of unconformities between older units in conjunction with geological maps and cross sections to argue that the front of the Zagros Simply Folded Zone has propagated in time and space. These unconformities indicate that deformation started as early as end Eocene in the northeast of the Simply Folded Zone and propagated progressively to the southwest, where unconformable contacts are only seen between younger units. As shortening continued, the southwest migration of the deformation front drove the foreland basin in front of it to its present position along the Persian Gulf and Mesopotamia. The climax of orogeny took place at end Pliocene time when the most extensive unconformity in the Zagros Simply Folded Zone developed between the (upper) Bakhtyari Formation and older units. Active seismicity and documented present uplift imply that the Simply Folded Zone is still propagating southwestward.
A tectonic origin for ironstone horizons in the Zimbabwe craton and their significance for greenstone belt geology
Authors: Hofmann A. , Dirks P.H.G.M. , Jelsma H.A. , Matura N.
Published: December 2007

Metre-thick horizons of ironstone lithologically similar to ‘sulphide-facies’ banded iron formation, but interpreted as silicified and sulphide-impregnated shear zones, are a common component of the greenstone stratigraphy of the Archaean Zimbabwe craton. Such tectonic ironstones separate different lithostratigraphic units commonly regarded as autochthonous rock sequences. On outcrop scale, shearing along ironstone horizons is indicated by anastomosing foliation domains, folding, boudinage and mylonitic fabrics, and, on a regional scale, by truncation of bedding and/or foliation, an anastomosing geometry of the horizons and duplication or juxtaposition of lithostratigraphic units. Tectonic ironstone formation is attributed to
in situ
silicification and iron (sulphide)-impregnation of rocks, commonly sediments, by mineralized fluids that penetrated the shear zones and their immediate wall rocks. The shear zones formed as a result of thin-skinned thrust tectonics that gave rise to horizontal accretion, imbrication and juxtaposition of volcanic and sedimentary rock units before deformation associated with granitoid diapirism. As a result, ‘layer-cake’ stratigraphic models of greenstone sequences containing tectonic ironstone ‘layers’ have to be treated with care, and the use of ironstone horizons as stratigraphic markers should be discouraged.
Incised valley fill stratigraphy of the Upper Cretaceous succession, proximal Orange Basin, Atlantic margin of southern Africa
Authors: Stevenson I.R. , McMillan I.K.
Published: December 2007

Seismic stratigraphic analysis of a grid of 7860 km of shallow seismic Sleevegun data, plus lithological and biostratigraphic (foraminifera) data interpreted from core and sea-bed samples have been integrated into a detailed geological model for the Upper Cretaceous succession of the proximal Orange Basin. Emphasis has been placed on the palaeoenvironmental interpretation of incised valley fill sequences of this succession. Seismic reflection geometries for the Middle Albian to Lower Cenomanian interval show that the entire coast was dominated by aggradational fluvial braid-plain facies. The Lower Turonian to Upper Coniacian succession marks the appearance of repeated major incision into the exposed coastal plain by large fluvial drainage networks. This succession is characterized by fourth-order, fluvial-to-marine sequences, with valley incision up to 25 km wide and 70 m deep. Detailed palaeoenvironmental analysis indicates periodically waterlogged, highly reducing fluvial floodplain environments with valley systems that were flooded to create wave-dominated estuaries. Major fluvial activity during the Turonian was in an area that lies offshore of the present-day Swartlintjies to Groen River mouths in the southern part of the Orange Basin. During the Coniacian the site of fluvial activity changed to the central Orange Basin, offshore of the present-day Buffels River. These observations contradict previously published views that a dominant Orange River drainage system existed since the Albian, at a position coincident with the present-day mouth.
A tectonostratigraphic synthesis of the Sub-Andean basins: implications for the geotectonic segmentation of the Andean Belt
Authors: Jacques JohnM.
Published: December 2007

The tectonic, structural and depositional history of 19 Sub-Andean foreland and eight southern Caribbean basins has been synthesized and is summarized by regional geohistory charts. These charts recapitulate the subsidence regimes recognized and have been used to evaluate correlations between genetically related stratigraphic sequences. Based on spatial and temporal changes in palaeo-depositional setting, the Sub-Andean region can be subdivided longitudinally into several tectonostratigraphic domains. The differential amount of subsidence between two adjacent tectonostratigraphic provinces or sub-provinces relies on the presence of a transverse zone of structural accommodation. The location of these transfer zones correlates with a number of known and several newly identified zones of intracontinental deformation. Combined with changes in the structural geometry of the Andean Fold and Thrust Belt and the relative dominance of basement fault systems along the length of the Andean foreland, it is suggested that the Andean Belt can be separated into five tectonic domains (which are themselves bounded by transverse, structural accommodation zones). Representing the multiphase reactivation of pre-existing basement fault systems, the influence of these broad zones of transcontinental deformation is most apparent during the Triassic–Jurassic period, suggesting that they were intimately associated with accommodating intraplate stresses during the breakup of the Gondwana Supercontinent.
Interactions between volcanism, rifting and subsidence: implications of intracaldera palaeoshorelines at Taupo volcano, New Zealand
Authors: MANVILLE V. , WILSON C.J.N.
Published: December 2007

At Taupo volcano (New Zealand), a major young caldera system is superposed on the Taupo Fault Belt, a zone of Late Quaternary extensional normal faulting accompanying rifting. Palaeoshorelines formed at 26.5 and 1.8 ka around intracaldera Lake Taupo highlight contrasts between short-term vertical deformation patterns detected by geodetic and lake-levelling surveys, and longer-term trends recorded by the warped and offset palaeoshoreline levels. Rifting is apparently occurring without the accumulation of long-term vertical offsets and net subsidence on adjacent normal faults of the Taupo Fault Belt. Geomorphic and stratigraphic data indicate that much vertical deformation is episodic and closely related to major volcanic eruptions: at other times, compensation is occurring, possibly by magma accumulation in the crust. However, periods of caldera unrest at Taupo may reflect regional rifting processes made manifest by the presence of the lake, rather than magmatic processes alone.
Basement evolution of the Sierra de la Ventana Fold Belt: new evidence for Cambrian continental rifting along the southern margin of Gondwana
Authors: Rapela C.W. , Pankhurst R.J. , Fanning C.M. , Grecco L.E.
Published: December 2007

U–Pb sensitive high-resolution ion microprobe data together with geochemical and Nd isotope analyses obtained in the basement complex of the Sierra de la Ventana Fold Belt indicate that the Early Palaeozoic passive margin history of the basin followed Cambrian magmatism related to rifting in a 600 Ma Neoproterozoic crust. The Cambrian episode started with intrusion of 531 ± 4 and 524 ± 5 Ma A- and I-type granites derived from a dehydrated infracrustal source (
ε
Nd
530
−3.1 to −5.9), and culminated with eruption of high-Zr peralkaline spherulitic rhyolites derived from an undepleted lithospheric mantle (509 ± 5 Ma;
ε
Nd
509
+0.5 to +1.0). These rift-related magmatic rocks were covered by shelf sediments deposited along a once-continuous passive margin, encompassing the Sierra de la Ventana Fold Belt, the Cape Fold Belt, the Falkland/Malvinas microplate and the Ellsworth Mountains block in Antarctica. The Cambrian rifting event defined the outline shape of the southern part of Gondwana, and can be regarded as the initiation of the supercontinent stage, which lasted until Jurassic break-up. The conjugate continental fragments separated from Gondwana during the Cambrian rifting could be the source for microcontinents with
c
. 1000 Ma basement rocks that collided with the proto-Andean margin during Ordovician–Silurian times.
Compositional variation during monogenetic volcano growth and its implications for magma supply to continental volcanic fields
Authors: NÉmeth K. , White J.D.L. , Reay A. , Martin U.
Published: December 2007

Individual volcanoes of continental monogenetic volcanic fields are generally presumed to erupt single magma batches during brief eruptions. Nevertheless, in two unrelated volcanic fields (the Waipiata volcanic field, New Zealand, and the Miocene–Pliocene volcanic field in western Hungary), we have identified pronounced and systematic compositional differences among products of individual volcanoes. We infer that this indicates a two-stage process of magma supply for these volcanoes. Each volcano records: (1) intrusion of a basanitic parent magma to lower- to mid-crustal levels and its subsequent fractionation to form a tephritic residual melt; (2) subsequent transection of this reservoir by a second batch of basanitic melt, with tephrite rising to the surface at the head of the propagating basanite dyke. Eruption at the surface then yields initial tephrite, typically erupted as pyroclasts, followed by eruption and shallow intrusion of basanite from deeper in the dyke. By analogy with similar tephrite–basanite eruptions along rift zones of intraplate ocean-island volcanoes, we infer that fractionation to tephrite would have required decades to centuries. We conclude that the two studied continental monogenetic volcanic fields demonstrate a consistent history of early magmatic injections that fail to reach the surface, followed by capture and partial eruption of their evolved residues in the course of separate and significantly later injections of basanite that extend to the surface and erupt. This systematic behaviour probably reflects the difficulty of bringing small volumes of dense, primitive magma to the surface from mantle source regions. Ascent through continental crust is aided by the presence in the dyke head of buoyant tephrite captured during transection of the earlier-emplaced melt bodies.
Effect of spatial distribution of Hormuz salt on deformation style in the Zagros fold and thrust belt: an analogue modelling approach
Authors: Bahroudi Abbas , Koyi HeminA.
Published: December 2007

Scaled analogue models of thin-skinned simultaneous shortening above adjacent viscous and frictional décollements simulate the effect of Hormuz salt on the shortening in the Zagros fold and thrust belt. The models consisted of sand layers that partly overlay a viscous layer of silicone and were shortened from one end. Spatial distribution of the viscous décollement varied along strike and dip, as occurs in part of the Zagros fold and thrust belt. In this belt, Phanerozoic sedimentary cover was shortened partly above the Hormuz salt lying on the Precambrian crystalline basement, behaving as a basal viscous décollement. Model results display how the nature of the décollement affects the evolution of an orogenic belt. Using model results, we explain the development of deflection zones, and discuss strain partitioning, formation of different topographic wedges and differential sedimentation along the Zagros fold and thrust belt. Model results suggest the formation of a gentle taper, consisting of both foreward and backward thrusts above a viscous décollement and a relatively steeper taper consisting only of forward-vergent imbricates above a frictional décollement. However, in our models, the steepest wedge with the highest topography formed where the viscous substrate had a limited extent with a transitional boundary (pinch-out) perpendicular to the shortening direction. Shortening of this boundary led to development of frontal ramps associated with significant uplift of the area behind the deformation front.
U–Pb geochronology of late Neoproterozoic augen granites in the Moine Supergroup, NW Scotland: dating of rift-related, felsic magmatism during supercontinent break-up?
Authors: Kinny P.D. , Strachan R.A. , Kocks H. , Friend C.R.L.
Published: December 2007

Within the Caledonides of Caithness, Scotland, the Neoproterozoic metasedimentary rocks of the Moine Supergroup are intruded by minor sheets of strongly deformed granite. U–Pb sensitive high-resolution ion microprobe zircon ages of 599 ± 9 Ma (Berriedale augen granite) and 588 ± 8 Ma (Braeval augen granite) are interpreted to date emplacement during the late Neoproterozoic. These augen granites are therefore unrelated to either Knoydartian (
c
. 870–790 Ma) or Caledonian (
c
. 470–420 Ma) orogenesis in the Scottish Highlands. Intrusion was, however, broadly contemporaneous with late Neoproterozoic extension of the Laurentian margin during continental break-up and the opening of the Iapetus Ocean. In the context of evidence for rift-related mafic magmatism within the Dalradian basin in Scotland at
c
. 600 Ma, as well as contemporaneous anorogenic magmatism along the margins of the developing Iapetus Ocean in the Appalachians, we propose that the protoliths of the augen granites were probably emplaced during continental break-up. The new data broaden the extent of this late Neoproterozoic magmatic event in the Scottish Highlands: other deformed granites that are at present undated but have been assumed to be of Caledonian age therefore require reinvestigation.
Provenance and geochemistry of sedimentary components in the Volcano-Sedimentary Complex, Iberian Pyrite Belt: discrimination between the sill–sediment-complex and volcanic-pile models
Authors: Boulter C.A. , Hopkinson L.J. , Ineson M.G. , Brockwell J.S.
Published: December 2007

Two highly contrasting models have been proposed for the palaeovolcanological setting of the massive sulphide deposits in the Iberian Pyrite Belt. The long-standing view of the host rocks is that they are a pile of effusive and pyroclastic rocks but this position has now been challenged by the proposal that high-level peperitic sills predominate. Discrimination between the volcanic-pile and sill–sediment-complex models is important because they lead to very different conclusions about such key metallogenic features as the timing of mineralization, the nature of the ore-forming convective system and the source of the metals. Sedimentary geochemistry, particularly REE and Ti/Nb, shows that there is no correspondence between the chemistries of mafic igneous sheets and intercalated stratified-volcaniclastic rocks that range from andesite to rhyodacite in composition. Therefore none of the mafic sheets supplied detritus to the sedimentary environment. Sedimentary rocks of continental provenance persist throughout the host-rock sequence, especially in mineralized regions, implying confinement of the majority of primary volcanic facies in the form of high-level intrusions. Some andesitic and felsic intrusions created a minor, stratified volcaniclastic component via hydrovolcanic eruptions. The volcanic-pile model is invalidated because the expected provenance patterns for this volcanic style are not present and the sill–sediment-complex setting of the sulphide deposits is confirmed.
Structural and thermal history of poly-orogenic basement: U–Pb geochronology of granitoid rocks in the southern Menderes Massif, Western Turkey
Authors: Gessner Klaus , Collins Alan S. , Ring Uwe , GÜngÖr Talip
Published: December 2007

Ion microprobe U–Pb dating of granitoid rocks from key structural outcrops of the Menderes Massif in western Turkey provides an important constraint to the thermal and deformational history of a structurally complex metamorphic belt within the Alpine chain. Crystallization ages of two granite protoliths, derived from the weighted means of rim ages and the ages of homogeneous prismatic zircon grains, are 541 ± 14 Ma and 566 ± 9 Ma, whereas the cores of zoned pyramidal and short-prismatic zircon grains range from Palaeoproterozoic to Neoproterozoic in age. These ages indicate that amphibolite- to granulite-facies metamorphic rocks in much of the Menderes Massif were deformed, metamorphosed and intruded during the Pan-African Orogeny, and neither crystallized nor remelted during an Alpine event. Structural and metamorphic evidence for Alpine convergence in Pan-African basement rocks is limited to greenschist-facies top-to-the-south shear zones, which occur on a regional scale across a number of tectonic units.
Strains and displacements in the Mam Tor landslip, Derbyshire, England
Authors: Rutter E.H. , Arkwright J.C. , Holloway R.F. , Waghorn D.
Published: December 2007

The spectacular Mam Tor landslip, near Castleton, Derbyshire, formed over 3000 years ago on an oversteepened slope left after the last ice age. A section of the Namurian Edale mudstones and overlying Mam Tor sandstones has collapsed, leaving an 80 m high scar on the eastern side of Mam Tor. The slip is about 750 m long and nearly 300 m wide and has the old main road from Manchester to Sheffield built across it. The slipped mass is in a state of year-on-year creep motion, which over the 190 years since the construction of the highway has led to extensive damage to the road, culminating in its closure in 1979. Since 1996 we have carried out annual monitoring by electronic distance measurement of the movement of a network of some 30 stations on the slipped mass. The average movement rate of the whole mass is about 10 cm a
−1
, with the central region moving significantly faster, at almost 50 cm a
−1
. Thus substantial readjustments of mass are taking place within the landslip. Local vertical displacements are systematically related to horizontal offsets, and the ratio of the two allows inference of the local attitude of the basal slip surface. The development of surface morphological features (pressure ridges and irregular topography, shear offsets on the highway, bulging of the road surface) reflects the lateral variations in displacement rate. Comparison of our survey of the present-day road position with that recorded in the topographical survey of 1880 shows a total 40 m downhill displacement of the highway over 122 years. This is consistent with extrapolation of our measured displacement rates back to 1880. Displacement rates within this period are, however, clearly higher than during the past 3000 years. There is a fairly clear correlation between vertical and horizontal displacement rates and annual variations in rainfall, with accelerated displacements following winter rainfall above a critical threshold level. Using survey points to define nodal points of a network of triangles, we have analysed the distribution of strain within the slipped mass. This revealed a pattern of continuous strain variations comparable with that found in flowing glaciers. In the lower part of the slip, horizontal strains are contractional and triangle areas are decreasing, causing some uplift of the ground relative to the general downhill flow on the basal slip surface. In the uphill part, strains are extensional and triangle areas are increasing. The new data allow an estimate of the time-dependent rheological behaviour of the sheared mudstone in the basal shear zone. The shear stress vs. shear strain rate relationship is very non-linear, with significant shear strain rates occurring only at shear stress levels within 10% of that required for rapid (catastrophic) shearing.
Fossil-wood carbon-isotope stratigraphy of the non-marine Wealden Group (Lower Cretaceous, southern England)
Authors: Robinson Stuart A. , Hesselbo Stephen P.
Published: December 2007

Fossil-wood carbon-isotope data are presented for the Wessex Formation, a non-marine unit within the Lower Cretaceous (Valanginian–Barremian) Wealden Group of the Isle of Wight and Dorset, southern England. The carbon-isotope values have a range (δ
13
C
c
. −26.6 to −19.8‰) that is consistent with that expected for Mesozoic C
3
plants. Consideration of the Isle of Wight fossil-wood carbon-isotope data together with data from Dorset allows construction of a composite fossil-wood carbon-isotope curve for almost the entire Wealden Group. The new carbon-isotope curve is in smooth continuity with data previously published from the overlying lagoonal Vectis Formation and marine Lower Greensand Group of Aptian age. A tentative correlation with a Tethyan reference carbon-isotope curve allows the provisional application of stage-level chronostratigraphy to the Wealden Group. Correlations suggest that the Wealden Group sediments are dominantly of Hauterivian and Barremian age and that the Valanginian is either condensed or partially missing. The carbon-isotope data presented indicate that even during times of relative carbon-cycle quiescence atmosphere CO
2
faithfully tracks the carbon-isotopic composition of the oceanic reservoir.
A tectonic pulse in the Makran accretionary prism recorded in Iranian coastal sediments
Authors: Hosseini-Barzi Mahboobeh , Talbot Christopher J.
Published: December 2007

Many recent studies of syndeformational sediments in a wide range of tectonic environments have improved our understanding of the development of individual or regional deformation structures. Here, we report studies of growth strata that imply an unexpected tectonic history within part of the Makran accretionary prism, currently the largest on Earth. We interpret the lithostratigraphy and ichnofacies of Plio-Pleistocene marine deposits logged along part of the Makran coast in terms of their palaeoenvironments. Lateral trends in thickness and depositional facies of rock units (and erosional surfaces among them) are correlated and then related to displacements along syndepositional faults that are distinguishable from changes in global sea level. Past studies of accretionary prisms have emphasized thrusting at the deformation front offshore. However, at the shoreline we find episodes of deposition during subsidence, as a result of oblique-slip normal faulting, alternating with episodes of erosion during uplift, driven by oblique-slip thrusting. The absolute timing of these displacements is not yet known. However, faults above a deep zone of subcretion (or underplating), well behind the surficial deformation front, have clearly undergone episodic reversals in throw that imply alternations in lateral shortening and extension.
Geomorphological evolution of Montserrat (West Indies): importance of flank collapse and erosional processes
Authors: Le Friant A. , Harford C.L. , Deplus C. , Boudon G. , Sparks R.S.J. , Herd R.A. , Komorowski J.C.
Published: December 2007

Analysis of topography and new swath bathymetry as well as geophysical data provides information about aerial and submarine morphological features and mass transfer processes on Montserrat. The island has a characteristic shallow (<100 m) submarine shelf, interpreted as having been formed through erosion with a depth controlled by glacio-eustatic sea-level variation. Several debris avalanche deposits are identified on the lower submarine flanks of Soufrière Hills volcano, and there is evidence of lateral collapses at the older volcanic centres. The morphological evolution of Montserrat is interpreted in terms of three stages. The first stage comprises submarine growth. The second stage, subaerial growth, is represented by the active South Soufrière Hills–Soufrière Hills volcanic centre. During the current eruption of Soufrière Hills volcano (1995–2002) more than half of the lava erupted was transported into the sea. Flank collapses occurred several times during this stage, such as the English's Crater event (
c
. 4000 years ago) or the Boxing Day event during the current eruption (26 December 1997). Montserrat's older volcanic centres, the Centre Hills and Silver Hills, illustrate the third stage of evolution, extinction and erosion. Magma production, long-term erosion and total sedimentation rates on Montserrat have been estimated as 0.17 km
3
ka
−
1
, 0.0125 km
3
ka
−
1
and 0.11 km
3
ka
−
1
(i.e. 1.1 cm ka
−
1
), respectively.
Variscan structure of the inner Bristol Channel, UK
Authors: Miliorizos M. , Ruffell A. , Brooks M.
Published: December 2007

Major Variscan structures under the Bristol Channel are concealed beneath a Mesozoic and Quaternary cover. Mapping of reflectors on offshore seismic sections reveals two major WNW–ESE-striking thrusts within the underlying Palaeozoic sequence. The more southerly, with a moderate SSW dip, has previously been identified as the Bristol Channel Thrust. Another thrust, the previously undescribed Gravel Margin Thrust, has been identified in the eastern part of the inner Bristol Channel and lies in the footwall of the Bristol Channel Thrust. It has a similar strike but steeper dip and extends to anticipated Precambrian basement depths. The Bristol Channel and Gravel Margin Thrusts together juxtaposed the contrasting Palaeozoic successions of South Wales and SW England before Mesozoic reactivation. Reflection packages identified on the offshore seismic sections are tentatively correlated with specific onshore Palaeozoic sequences. Interpretation of the offshore seismic sections in conjunction with geological mapping along the north Devon coast shows that the Bristol Channel and Gravel Margin Thrusts have orientations and geometries typical of several mesoscale thrusts observed and measured at Foreland Point, north Devon. Along-strike structural changes beneath the inner Bristol Channel seen on seismic sections provide evidence, additional to earlier refraction and structural studies, for the offshore continuation of the NW–SE-trending Watchet–Cothelstone–Hatch Fault and its linkage with the previously described Central Bristol Channel Fault Zone. The Bristol Channel and Gravel Margin Thrusts are interpreted to be offset from the Cannington Park Thrust in north Somerset by a 14–16 km Variscan dextral strike-slip displacement across the Watchet–Cothelstone–Hatch Fault. The Bristol Channel Gravel Margin Thrust and the Cannington Park Thrust are interpreted as syngenetic structures linked by their lateral ramp, the Watchet–Cothelstone–Hatch Fault. Using all the above information, the overall structure of the Variscides of the inner Bristol Channel is re-evaluated and a new tectonic model is presented. The structures discussed in this paper, at a scale portrayed by commercial seismic data and published geological maps, may represent merely the tips of linked thrusts that have previously been mapped down to mid-crustal depths on BIRPS seismic sections from the South West Approaches Traverse. We show that enough data now exist to resolve outstanding problems of the concealed Variscan structure in the inner Bristol Channel, providing local structural detail that can be incorporated into the wider tectonic framework of NW Europe.
Strain, deformation temperatures and vorticity of flow at the top of the Greater Himalayan Slab, Everest Massif, Tibet
Authors: Law R.D. , Searle M.P. , Simpson R.L.
Published: December 2007

This paper presents quantitative data on strain, deformation temperatures and vorticity of flow at the top of the Greater Himalayan Slab. The data were collected from the Tibetan side of the Everest Massif where two low-angle normal faults bound the upper surface of the Greater Himalayan Slab, the earlier and structurally lower Lhotse Detachment and the later and structurally higher Qomolangma Detachment. Greenschist- to sillimanite-grade quartz-rich metasedimentary rocks exposed in the Rongbuk to North Col region of the Everest Massif are characterized by cross-girdle quartz
c
-axis fabrics indicating approximate plane strain conditions. Fabric opening angles progressively increase with depth beneath the overlying Lhotse Detachment, and indicate progressively rising deformation temperatures of 525–625 ± 50 °C at depths of 300–600 m beneath the detachment. Deformation temperatures of
c
. 450 °C are indicated by fabric opening angles in epidote amphibolite-facies mylonites located closer to the overlying detachment. A top down-to-the-north (normal) shear sense is indicated by the asymmetry of microstructures and
c
-axis fabrics, but the degree of asymmetry is low at distances greater than 400 m beneath the detachment, and sillimanite grains are drawn into adjacent conjugate shear bands but still appear pristine, indicating that deformation occurred at close to peak metamorphic temperatures. These ‘quenched’ fabrics and microstructures indicate rapid exhumation in agreement with previous isotopic dating studies. Mean kinematic vorticity numbers (
W
m
) were independently calculated by three analytical methods. Calculated
W
m
values range between 0.67 and 0.98, and indicate that although a simple shear component is generally dominant, particularly in greenschist-facies mylonites located between the Lhotse and overlying Qomolangma detachments, there is also a major component of pure shear in samples located at 400–600 m beneath the Lhotse Detachment (pure and simple shear make equal contributions at
W
k
=0.71). Our integrated strain and vorticity data indicate a shortening of 10–30% perpendicular to the upper surface of the Greater Himalayan Slab and confirm that the upper surface of the slab is a ‘stretching fault’ with estimated down-dip stretches of 10–40% (assuming plane strain deformation) measured parallel to the flow plane–transport direction.
Re–Os isotopic age constraints on deposition in the Neoproterozoic Amadeus Basin: implications for the ‘Snowball Earth’
Authors: SCHAEFER B.F. , BURGESS J.M.
Published: December 2007

Re–Os isotopes have been measured on organic-rich sedimentary rocks from the Neoproterozoic Aralka Formation in the Amadeus Basin, central Australia. These sedimentary rocks closely predate the Marinoan glaciation, a correlative of the global ‘Snowball II’ event. The Aralka Formation sedimentary rocks preserve an age of 592 ± 14 Ma, which is interpreted to represent the age of deposition. This age is substantially younger than that inferred from global correlation studies. It indicates that the onset, duration and cessation of the glacial event, and subsequent deposition of >2 km of sediment prior to radiation of the earliest metazoan life assemblages is confined to
c.
40 million years.
Intraplate deformation in the NW Iberian Chain: Mesozoic extension and Tertiary contractional inversion
Authors: GuimerÀ Joan , Mas RamÓn , Alonso Ángela
Published: December 2007

The Iberian Chain developed within the Iberian plate during the Palaeogene and Early Miocene as a result of convergence between the African and Eurasian plates. It is a fold-and-thrust belt, which involves the Hercynian basement and the Mesozoic and Cenozoic cover. A generalized cross-section of the NW part of the Chain, of 195 km length, is presented. Mesozoic basins, developed on the Hercynian basement, display thickness variations across normal faults that bounded them and that can be recognized in the field. The Tertiary contraction deformed and inverted the Mesozoic basins, and it is inferred to have produced a thrust sheet about 5 km thick in its frontal (northeastern) part, which thickens to the SW. The total Tertiary shortening in the section is 66.6 km (26%). The structure and the crustal shortening and thickening of the Iberian Chain are explained by a major upper-crustal thrust system with simple flat-and-ramp geometry, which may branch to the Pyrenees or the Betics. This is combined with internal deformation of the thrust sheet. The contribution of the Iberian Chain shortening to the convergence of the African and Eurasian plates during the Tertiary is about one-half of that of the Pyrenees, and should be taken into account in any reconstruction of the kinematics of these plates.
Detachment faulting and bimodal magmatism in the Palaeoproterozoic Willyama Supergroup, south–central Australia: keys to recognition of a multiply deformed Precambrian metamorphic core complex
Authors: Gibson George M. , Nutman Allen P.
Published: December 2007

The multiply deformed (D
1
–D
3
) Palaeoproterozoic Willyama Supergroup in south–central Australia incorporates upper and lower
c
. 1700 Ma metasedimentary sequences with contrasting early tectonothermal histories that invite comparisons with the metamorphic core complexes and younger extensional orogens of western North America and Europe. A detachment surface of D
1
age separating these two sequences has the deduced geometry of an extensional shear zone, juxtaposing rocks subjected to bimodal magmatism, sillimanite- to granulite-grade migmatization, and Na–Fe metasomatism against a less intensely metamorphosed upper plate lacking both migmatites and bimodal magmatism. Synextensional metamorphism took place under low-pressure–high-temperature conditions, producing regionally extensive andalusite- and sillimanite-bearing mineral assemblages before further high-grade metamorphism accompanying D
2
recumbent folding and crustal thickening. D
2
folding locally inverted the original D
1
thermal structure so that sillimanite-grade lower plate rocks now lie structurally above andalusite-grade rocks of the upper plate, rendering recognition of the original detachment surface and associated thermal structure difficult. U–Pb dating of synextensional metabasites intruded into lower plate rocks just below the detachment surface indicate that extension and related bimodal magmatism peaked around 1690–1670 Ma, some 70–90 Ma earlier than the 1600–1590 Ma age previously inferred for the onset of regional deformation and low-
P
–high-
T
metamorphism. A regionally extensive redox boundary associated with the detachment surface served as the locus for several important mineral deposits.
Reappraisal of the K–T boundary succession at Stevns Klint, Denmark
Authors: Hart Malcolm B. , Feist Sean E. , Price Gregory D. , Leng Melanie J.
Published: December 2007

We present stratigraphical and stable isotope data (
δ
13
C,
δ
18
O) for two successions selected from the K–T boundary succession seen in the cliff sections of Stevns Klint (Denmark). Although the succession at Højerup is well known from other studies, that at Kulstirenden has not been described before. It contains an exceptionally thick (
c
. 40 cm) development of the boundary clay (or Fish Clay), which includes the ‘red layer’ just above its base. There is clear evidence of shallowing in the latest Maastrichtian in advance of the K–T boundary, together with fluctuations in sea-water temperature. The detailed
δ
13
C record at Kulstirenden provides a record of the environmental changes within the boundary interval with a resolution better than many other successions described in the literature.
Modelling oceanic carbon and phosphorus fluxes: implications for the cause of the late Cenomanian Oceanic Anoxic Event (OAE2)
Authors: Nederbragt Alexandra J. , Thurow JÜrgen , Vonhof Hubert , Brumsack Hans-J.
Published: December 2007

A two-box ocean model with a coupled carbon and phosphorus cycle is used to test which processes can realistically generate a rapid positive 2‰ δ
13
C excursion in the global carbon reservoir. Internal oceanic processes (enhanced preservation of organic matter under anoxic conditions, enhanced upwelling) cannot produce a substantial δ
13
C excursion under the assumption that burial rates of C and P are coupled. Loss of nutrients to the sediment acts as a negative feedback mechanism that prevents a substantial perturbation of the carbon cycle. A large and renewable source of nutrients is needed, either from increased continental weathering or from enhanced regeneration of sedimentary organic phosphorus under anoxic conditions. Measurements of total phosphorus and organic carbon in sediments from the Tarfaya Basin, Morocco, suggest that a large decrease in P burial occurred relative to organic carbon at the base of the Cenomanian–Turonian Oceanic Anoxic Event (OAE2), with the right magnitude to quantitatively explain a 2‰ shift in δ
13
C. It is concluded that the main underlying mechanism that allowed and sustained enhanced carbon burial during the mid-Cretaceous was a perturbation of the oceanic phosphorus cycle.
Timing of high-grade metamorphism in central Turkey and the assembly of Anatolia
Authors: Whitney Donna L. , Hamilton Michael A.
Published: December 2007

The timing of metamorphism of the crystalline massifs in western and central Turkey (Menderes, Kırșehir, Nigde, Akdag) is important information for understanding the assembly of Anatolia and the thermal–tectonic evolution of the Turkish segment of the Alpine–Himalayan belt. The high-grade basement rocks of the massifs are polymetamorphic, and the complexity of interpreting ages obtained from zircon and other minerals has led to a longstanding debate about the significance and regional extent of Neoproterozoic v. younger (Mesozoic, Cenozoic) metamorphism. New U–Pb SHRIMP (sensitive high-resolution ion microprobe) analyses of monazite from a garnet–sillimanite gneiss in the Kırșehir Massif, central Anatolia, document Late Cretaceous (84.1 ± 0.8 Ma) high-temperature metamorphism. This Late Cretaceous age for central Anatolian metamorphism is at least 50 Ma older than Alpine metamorphism in the Menderes Massif in western Turkey. Models that propose a continuous Anatolide–Tauride tectonic zone, with central Anatolia as a promontory, cannot explain such a large time difference within a small region. Unless the Menderes ages have been reset by Aegean thermal–tectonic events, Anatolia probably formed from a collage of continental fragments rather than by simple collision of an irregular Tethyan platform with Eurasia.