bluuebunny/crossref_metadata_2025_split huggingface dataset:
Holocene coastal dune initiation in Northumberland and Norfolk, eastern UK: climate and sea-level changes as possible forcing agents for dune initiation
Authors: Orford J. D. , Wilson P. , Wintle A. G. , Knight J. , Braley S. 
Published: April 2008

Abstract

Relative sea-level (RSL) control on dune initiation during the Holocene is examined in the context of chronostratigraphies established from 43 vibracores through dunes and into sub-dune sediments taken from the Northumberland and Norfolk (UK) coasts. The chronology is based on 23 accelerated mass spectroscopy and conventional
14
C dates, and 37 infra-red-stimulated luminescence dates. The oldest dunes in Northumberland are
c.
4 cal. ka
bp
with phases of dune development at 2.8 and 1.5–1 ka
bp
. Most dune deposition is of last millennium age, with a concentration, especially in Norfolk, around 500–200 a
bp
. The initiation and survival of coastal dune sequences relate to macroscale RSL changes over the last 4 ka. Northumberland dunes reflect a gradient of RSL change from a northern RSL fall (forced regression) through to a southern RSL rise (normal regression through sediment supply). The north Norfolk coast has been dominated by a rising RSL through the Holocene, though associated with a sediment supply sufficient to offset the transgressive tendency and allow normal regressive deposition at numerous positions along the coast over the last 1 ka. It is suggested that the development of Little Ice Age (LIA) dunes in both Norfolk and Northumberland identifies the onset of specific conditions in which intertidal sediment sources were exposed (falling sea-level) to onshore winds (LIA circulation changes), which reflect a brief west North Sea period in dune initiation and deposition rates. A comparison of this consolidated dune chronology with statements of RSL elevation and climate conditions in the last 2.5 ka leads to some recognition of RSL fall preceding major dune building in two phases post 1.5 ka
bp
and post 0.6 ka
bp
.
Holocene sedimentary evolution and palaeocoastlines of the Fenland embayment, eastern England
Authors: Brew David S. , Holt Tina , Pye Ken , Newsham Rhonda 
Published: April 2008

Abstract

The Holocene sedimentary facies of the Fenland are described using a lithological database and new cores recovered as part of the Land-Ocean Interaction Study. Landward, the Holocene sequence is dominated by mud facies with intercalated peat layers, whereas the seaward areas are sand-dominated. The sedimentological characteristics of the mud facies are homogeneous and are similar for the whole sequence. Glacial deposits located north of The Wash are thought to be the main sediment sources. The sand facies generally fines upwards and the chemistry reflects this change. However, elemental ratios show only slight variations between the two facies implying a general constancy of sediment provenance. The evolution of the Fenland has been dominated by three main events. Firstly, the initial post-glacial transgression, which started
c.
7850 cal.
bp
. Secondly, the sedimentary infilling of the embayment with rising sea-level; deposition of intertidal clastic sediments alternating with peat accumulation. Thirdly, renewed expansion of tidal flat areas between
c.
2750 and 1500 cal.
bp
forming the final clastic fill.
Late Cretaceous and Tertiary structural evolution of the northeastern part of the Vøring Basin, Norwegian Sea
Authors: Mogensen Tommy Egebjerg , Nyby Rune , Karpuz Ridvan , Haremo Pål 
Published: April 2008

Abstract
The Late Cretaceous-Tertiary structural evolution of the northeastern part of the Vøring Basin, mid-Norway, is highly complicated. Although tectonic activity occurred throughout Cretaceous time in much of the Vøring Basin, including the Gjallar Ridge and along the Fles Fault Zone, in the Vema Dome-Nyk High area evidence of such activity is not observed until the latest Maastrichtian time. In the Vema Dome-Nyk High area, several faults with both a NW-SE orientation and a NE-SW orientation have experienced lateral movements. The NE-SW orientation is the old Caledonian trend. The complex structural evolution of the Vema Dome-Nyk High area is probably related to the existence of continental weakness zones, which are the onshore extension of known oceanic fracture zones. The two lineaments that delineate these weakness zones, and that delineate the Vema Dome-Nyk High area, namely the Bivrost and Surt Lineaments, diverge slightly from one another toward the SE. This complex structural framework of NW-SE oriented lineaments and NE-SW oriented deep-seated basement structures of Caledonian compressional and/or Mesozoic rift origin, facilitated minor clockwise rotation of the area between the two lineaments during the extensional regime before the break-up of the North Atlantic, as well as during the compressional regime that has been proposed after the break-up.
Norwegian-Greenland Sea thermal field
Authors: Sundvor Eirik , Eldholm Olav , Gladczenko Tadeusz P , Planke Sverre 
Published: April 2008

Abstract

Thermal gradient and thermal conductivity measurements carried out in the Norwegian-Greenland Sea and in the western Eurasia Basin from 1967 to 1996 have yielded 436 heat-flow values which have been stored on a UNIX-platform database,
heat
, to facilitate retrieval, documentation and display.
heat
contains all public domain data for the region, and the database and application programs are freely available. The heat flow on oceanic crust reveals a clear, first-order heat-flow-crustal-age relationship. The thermal conductivity is relatively uniform and consistent, with values in the 0.85–1.15 W m
−1
K
−1
range. The lower values are from the ocean basins and the higher values from the continental margins. Local, very high heat flow along the present spreading axis may imply active volcanism or venting. We also document local continental slope maxima on the Møre and western Barents Sea margins, contrasting greatly with the typical low heat flow, generally <75 m W m
−2
, on old oceanic and thinned continental crust. The abnormally high heat flow, exceeding 1000 m W m
−2
, on the ‘Håkon Mosby’ gas-seeping mud volcano on the Barents Sea margin suggests that also other local slope maxima may be related to active seeps.
A comparison of the geometry, spatial organization and fracture patterns associated with forced folds and buckle folds
Authors: Cosgrove J. W. , Ameen M. S. 
Published: April 2008

Abstract
In this paper the three-dimensional geometry and spatial organization of folds (both buckle folds and various types of forced folds) are considered, together with their associated fracture patterns, in an attempt to determine if these features can be used in regions of poor exposure or in areas where the geologist must rely on seismic data to indicate the type of folding that has occurred. This study of the relationship between the various fold types and associated fracture patterns draws on theoretical considerations of ideal conceptual models of folds, analogue models and field studies.
Forced-fold development within Tertiary sediments of the Alba Field, UKCS: evidence of differential compaction and post-depositional sandstone remobilization
Authors: Cosgrove John W. , Hillier Rob. D. 
Published: April 2008

Abstract
It is argued that the present trapping geometry within the Eocene Alba Field of the Outer Moray Firth, UKCS, has combined structural-stratigraphic elements. The structural component formed by significant topographic inversion of the deep-marine channel sandstones that constitute the field’s reservoir. A study of core and three-dimensional (3D) seismic demonstrates that topographic inversion took place in response to two processes. The first was differential compaction of mudstone over the channel resulting in a forced fold. This structure was further enhanced by post-depositional sandstone fluidization and remobilization, the latter being focused toward the structural crest of the sandstone body which formed the core of the forced fold. The process of post-depositional remobilization caused significant sand injection into the mudstone overburden and the formation of seismic-scale dykes at the margins of the channel fairway. The growth of the forced fold (by sand remobilization) and the position of the peripheral dykes is analogous to that of igneous intrusions, specifically laccoliths.
Extensional forced folding and décollement of the pre-rift series along the Rhine graben and their influence on the geometry of the syn-rift sequences
Authors: Maurin Jean-Christophe , Niviere Bertrand 
Published: April 2008

Abstract
On the western margin of the Rhine graben, forced folding and décollement of competent Dogger strata occurred during the latest Eocene-Early Oligocene (Priabonian) as a result of normal faulting in the basement. The Dogger series are represented by NNE-striking thick layers of oolitic limestones strongly disrupted by extensional structures and incipient boudinage. To the east, the overlying Priabonian (syn-rift) sequences exhibit divergent onlaps, steeply dipping intraformational unconformities and a general drag syncline geometry. These syn-depositional structures attest to a close control by the progressive tilting and normal dip-slip sliding of the Dogger strata. Interpretation of a shallow seismic reflection profile reveals that this tilting is related to an underlying master normal fault which dips 60–70° to the east. This fault offsets the Variscan crystalline basement and the gently dipping Triassic cover by about 2 km. To be balanced, the structural arrangement requires the presence of a décollement layer located between the top of the Triassic series and the Dogger series, corresponding to the Late Triassic incompetent gypsiferous clays and marls. The response of the competent Dogger to the imposed forced folding is through the development of a large-scale extensional syncline in the hangingwall of the master detachment, compensated by the development of a piggy-back half-graben in the footwall. In the light of this new interpretation, a mechanical hypothesis is proposed including a two-stage evolution model of extension and subsidence for the Rhine graben.
Predicting patterns of strain from three-dimensional fold geometries: neutral surface folds and forced folds
Authors: Lisle Richard J. 
Published: April 2008

Abstract
The geometries and densities of fractures associated with fold structures can be predicted by assuming that the strains accommodated by fractures mimic the bulk strains induced in the strata during folding. This paper examines, from a theoretical standpoint, the distributions of bedding-plane strains expected in folds formed by various folding mechanisms. The relationship between the state of bedding-plane strain and fold-surface geometry is found to vary according to different fold types, distinguished on the basis of their curvature properties. The first type are developable fold surfaces, which have Gaussian curvature equal to zero. Folding mechanisms which are dominated by the mechanical strength of the layering, such as buckling, produce surfaces of this type. Folds of this type allow the possibility of estimating the bedding-plane strains from the geometrical features of the folded layer. Neutral surface folds and flexural-slip folds are discussed as examples. The other main class of folds have non-developable surfaces, which have non-zero Gaussian curvature. Folded surfaces with this form arise predominantly from mechanisms that involve the passive deflection of the layering in response to displacement gradients originating outside of the layer, e.g. drape folding. Although the geometry of these surfaces implies the presence of bedding plane strains, the quantification of these strains cannot be made from the fold geometry but requires additional information on these displacement patterns.
Structural evolution of the western margin of the Nanga Parbat massif, Pakistan Himalaya: insights from the Raikhot-Liachar area
Authors: Butler R. W. H. 
Published: April 2008

Abstract
There are several competing interpretations of the structure of the margins of the Nanga Parbat massif: that the massif is bounded by the original suture between the Indian continent and the Kohistan-Ladakh island arc—the Main Mantle Thrust; that the massif is entirely bounded by neotectonic faults; that it is bounded by a combination of early and late faults and shear zones. If the marginal structures of the massif are to be related to local and regional geo-tectonic evolution then their correct characterization is critical. The Raikhot Bridge area on the western margin of the massif is useful in this regard, as it provides accessible and near-continuous outcrops. This contact, sometimes called the Raikhot Fault, is composite. Sheared metagabbros of the Kohistan arc are juxtaposed tectonically against metasediments and orthogneisses of the Nanga Parbat massif along an early ductile shear contact, developed under amphibolite facies conditions. In this regard it may be a preserved segment of the Main Mantle Thrust. However, this ductile shear zone has been strongly modified, flattened and rotated, and is cut by younger shears and faults. The original kinematics of the shear zone have been largely overprinted by these subsequent deformations. The younger structures include NE-SW striking, dextral strike-slip faults and a major top-to-NW thrust and shear zone. A sequence of metamorphism, deformation and igneous emplacement may be used to study the history of structural evolution within the massif. The use of a single name (e.g. Raikhot Fault) for the present-day map contact between the Nanga Parbat massif and neighbouring Kohistan is misleading. The early contact (termed here the Phuparash Shear Zone, possibly the northeastern continuity of the Main Mantle Thrust) is modified by the Buldar Fault Zone (dextral strike-slip) and the Liachar Thrust Zone (top-to NW carriage of the Nanga Parbat massif across the Phuparash Shear Zone and onto Kohistan). The activity of the Buldar Fault and Liachar Thrust Zone continued during exhumation of the massif, through amphibolite facies to the Earth’s surface. The interaction between these structures is at present unknown. However, establishing these and similar interactions within the Nanga Parbat area remain central to establishing the role of regional NE-SW dextral transpression in the modern structure of the massif.
Geological structure of the southern part of the Nanga Parbat massif, Pakistan Himalaya, and its tectonic implications
Authors: Butler R. W. H. , Wheeler J. , Treloar P. J. , Jones C. 
Published: April 2008

Abstract
The Nanga Parbat massif lies in the core of the major north-south trending, broadly upright antiform that marks the NW syntaxis of the Himalayan arc. However, this antiformal structure is not evident in the trend of foliation and banding within the central and southern parts of the massif. Reconnaissance field studies in this region (Astor, Rama and Rupal areas) have delineated an important shear zone with top-to-the-south overthrust kinematics. This Rupal Shear Zone carries the migmatitic core of the massif onto nonmigmatitic metasediments locally termed the Tarshing Group. The shear zone traces north into a broad high strain zone of steep foliation with gently plunging mineral elongation lineations with no consistent sense of shear. A tentative model is proposed whereby top-to-the-south overshear in the Rupal area passes northwards into a steep belt of apparently constrictional N-S elongation. This type of large-scale transpression may record the early growth of the syntaxis. However, relating these structures to Himalayan orogenesis and the amplification of the NW syntaxis is problematic. The Nanga Parbat massif displays a long and complex history of polyphase deformation, metamorphism and magmatism, as might be expected of a terrane derived from the basement of the Indian sub-continent. Although at least the later part of the constrictional steep belt developed with syn-kinematic leucogranite intrusions (< 10 Ma), the old age limit on the Rupal Shear Zone remains unconstrained.
Geochronological constraints on the evolution of the Nanga Parbat syntaxis, Pakistan Himalaya
Authors: Treloar P. J. , Rex D. C. , Guise P. G. , Wheeler J. , Hurford A. J. , Carter A. 
Published: April 2008

Abstract
New amphibole, muscovite and biotite Ar-Ar and K-Ar data and zircon and apatite fission track data are presented from the western margin of the Nanga Parbat syntaxis as well as from the Indus and Astor valley sections which cross the syntaxis. Amphibole data date a regional cooling through 500°C at 25±5 Ma and are inconsistent with earlier suggestions that the peak of regional metamorphism was Neogene in age, although there is no doubt that some rocks were still at upper amphibolite facies temperatures as recently as 5 Ma. The data can be used to constrain structural models for syntaxial uplift. After an initial phase of crustal-scale buckling, bodily uplift of the syntaxis was along subvertical shear zones developed along its margins, although with a significantly higher time-averaged strain rate for shears developed along the western margin than along the eastern margin. The latter may be antithetic to the former. These shears were operative from 10 to < 1 Ma. In the southwestern part of the syntaxis, this subvertical uplift was superseded, since 6 Ma, by uplift along moderately SE-dipping NW-vergent shears on the hanging wall of which are located Neogene-aged migmatites.
Pre-collisional anastomosing shear zones in the Kohistan arc, NW Pakistan
Authors: Arbaret L. , Burg J.-P. , Zeilinger G. , Chaudhry N. , Hussain S. , Dawood H. 
Published: April 2008

Abstract
Ductile strain localization commonly forms a pattern of shear zones anastomosing around lenses of less deformed rock. Initiation and development of anastomosing shear zones are studied through description of the structures and deformation history of plutonic rocks that form the lower crust of the Kohistan arc. Structures and textures developed in these rocks result from primary magmatic to solid state regional strain, overprinted by anastomosing shear zones. The primary strain was mainly acquired during magmatic emplacement at 100-90 Ma. Strain localization took place continuously from magmatic emplacement to solid state deformation during cooling of the plutons and formed three successive sets of shear zones. Set 1 is composed of associated discrete Riedel and thrust shear zones developed above solidus conditions during southwestward thrusting. Continuous deformation from solidus to amphibolite facies conditions between 100 and 83 Ma formed the second set of shear zones. The lower amphibolite facies set 3 shear zones are diffeentiated by larger strains recorded in the thicker mylonitic zones and enlargement of the spacing between shear zones during cooling. The anastomosing pattern of shear zones described here probably represents arc-related deformation during subduction of the Tethys oceanic lithosphere below the Kohistan arc.
Isotopic constraints on the evolution of metamorphic conditions in the Jijal-Patan complex and the Kamila Belt of the Kohistan arc, Pakistan Himalaya
Authors: Anczkiewicz R. , Vance D. 
Published: April 2008

Abstract

Pressure-temperature data and Sm-Nd and Rb-Sr garnet ages are presented for retrogressed granulitic rocks of the Jijal-Patan complex and the Kamila Amphibolite Belt. Despite the retrogression and hydration, the two samples contain garnet and hydrous minerals that yield pressures and temperatures similar to previous estimates for pristine granulite facies rocks from the same area. The Sm-Nd and Rb-Sr garnet ages are concordant at 95–100 Ma for the two samples and for both isotopic systems. These ages are interpreted as dating cooling through 700–800 °C following magmatic crystallization and granulite facies metamorphism. In the case of the garnet amphibolites from the Kamila Belt, the garnets retain prograde major element zonation. In addition, the closure temperature for the Rb-Sr system is very close to the recorded temperature. For these reasons, the age of 100 Ma must represent a time close to that when the pressure and temperature preserved in the mineralogy and its chemistry was recorded. The isotopic equilibrium between garnet and paragonite at 90–100 Ma suggests that the regional hydration event that affected the lower crust of the Kohistan arc also occurred at this time. Cooling rates calculated from the Rb-Sr and Sm-Nd ages for the partially retrogressed granulite give a minimum of 3–6°C Ma
−1
and imply a different tectonic mechanism for the exhumation of the lower crust than is typical for granulites. This process may be related to early regional decompression following the collision of the Kohistan arc with Eurasia.
The Main Mantle Thrust in Pakistan: its character and extent
Authors: DiPietro J. A. , Hussain A. , Ahmad I. , Khan M. A. 
Published: April 2008

Abstract
The Main Mantle Thrust (MMT) represents the tectonic boundary between metamorphic shield and platform rock of the Indian plate hinterland, and dominantly mafic and ultramafic rock of the Kohistan-Ladakh arc complex in Pakistan. In some areas, this boundary is a sharp planar fault with development of mylonite; in other areas, it is a brittle-ductile imbricate zone; in still other areas, it contains large, discontinuous, slices of internally sheared and deformed ophiolitic mélange. The character of the MMT along its entire trace is discussed and it is concluded that there is no single continuous fault which marks the contact between the Indian plate and the Kohistan-Ladakh arc. On this basis, we propose a revised definition for the MMT that is consistent with both the original definition and with the usage of the term in literature. We suggest that the MMT fault contact be defined as the series of faults, of different age and tectonic history, that collectively define the northern margin of the Indian plate in Pakistan. On this basis, faults that define the MMT vary in age from Quaternary to possibly as old as Late Cretaceous. Discontinuous lenses of ophiolitic mélange that overlie the MMT fault contact, and which intervene between the Indian plate and the Kohistan-Ladakh arc, are considered to be part of an MMT zone that is equivalent with the Indus Suture Zone.