bluuebunny/crossref_metadata_2025_split huggingface dataset:
Holocene isostasy and relative sea-level changes on the east coast of England
Authors: Shennan I. , Lambeck K. , Horton B. , Innes J. , Lloyd J. , McArthur J. , Rutherford M. 
Published: April 2008

Abstract

Analysis of sea-level data from the east coast of England identifies local-scale and regional scale factors to explain spatial and temporal variations in the altitude of Holocene sea-level index points. The isostatic effect of the glacial rebound process, including both the ice (glacio-isostatic) and water (hydro-isostatic) load contributions, explains regionalscale differences between eight areas:
c.
20 m range at 8 cal. ka
bp
and by 4 cal. ka
bp
relative sea-level in Northumberland was above present, whereas in areas to the south relative sea level has been below present throughout the Holocene. Estimates for pre-industrial relative sea-level change range from 1.04 ± 0.12 mm a
−1
in the Fenland to −1.30 ± 0.68 mm a
−1
(i.e. sea-level fall) in north Northumberland, although this may overestimate the current rate of sea-level fall. Isostatic effects will produce similar relative differences in rates of sea-level change through the twenty-first century. The data agree closely with the patterns predicted by glacio- and hydro-isostatic models, but small systematic differences along the east coast await testing against new ice models. Local scale processes identified include differential isostatic effects within the Humber Estuary and the Fenland, tide range changes during the Holocene, and the effects of sediment consolidation. These processes help explain the variation in altitude between sea-level reconstructions derived from index points taken from basal peats and those from peats intercalated within thick sequences of Holocene sediments.
Crustal structure in the northern North Sea: an integrated geophysical study
Authors: Christiansson P. , Faleide J. I. , Berge A. M. 
Published: April 2008

Abstract

This study focuses on the deep structure of the Viking Graben and adjacent areas of the northern North Sea (60–62°N), and its implications for the amount, timing and nature of lithospheric extension. Two regional transects have been constructed based on an integrated analysis of deep seismic reflection and refraction data, gravity and magnetic data, and correlations between offshore and onshore geology. The shallow interpretation is based on high-quality conventional seismic reflection data calibrated against a large number of exploration wells. The new and partly reprocessed seismic data, combined with the other geophysical data, make possible a better documentation of the crustal configuration, such as the pre-Jurassic sediment distribution, basement and Moho relief, and deep fault geometries. A lower-crustal body characterized by an 8+ km s
−1
velocity and an average bulk density of 2.95 g cm
−3
is present beneath the Horda Platform. This body probably represents a deep crustal root of partially eclogitized rocks that formed during the Caledonian orogeny. Heterogeneities within this body give rise to the non-typical velocity-density relation. The crust-mantle boundary is located at the base of this body at a depth of 30–35 km and does not coincide with the seismically defined Moho. The geometry of crustal thinning reflects the cumulative effect of several post-Caledonian rift phases. Results show that Permian rifting affected a wide area, from the Øygarden Fault Complex to the Hutton Fault.
Repeated lithosphere extension in the northern Viking Graben: a coupled or a decoupled rheology?
Authors: Ter Voorde M. , Færseth R. B. , Gabrielsen R. H. , Cloetingh S. A. P. L. 
Published: April 2008

Abstract
The Late Permian-Early Triassic and Jurassic-Cretaceous rift events that influenced the structure of the northern Viking Graben are examined. Here, a 2D forward numerical model including faults is applied on seismic line NVGT88-04, which crosses the basin in the E-W direction. We concentrate on (1) the amount of Jurassic basin subsidence that can be explained by thermal contracting resulting from the Permo-Triassic event, (2) the spatial connection between the two rift events and (3) the apparent mode of flexure (coupled v. decoupled) of the lithosphere. Modelling results indicate that post-rift subsidence as a result of Permo-Triassic rifting has practically ceased at the onset of Jurassic rifting. The position of the rift axis is shown to migrate with time, from the Horda Platform in Permo-Triassic time to the present Viking Graben centre in Jurassic-Cretaceous time. The major difference between the consequences of a coupled versus a decoupled mode of flexure is that the latter causes a larger amount of fault-block rotation. On this basis, we suggest a decoupled mode of flexure for the Permo-Triassic rift phase, a coupled mode of flexure for the Early Jurassic rift phase, and a decoupled mode of flexure again for the Late Jurassic period.
Cenozoic evolution of the central and northern North Sea with focus on differential vertical movements of the basin floor and surrounding clastic source areas
Authors: Jordt Henrik , Thyberg Brit I. , Nøttvedt Arvid 
Published: April 2008

Abstract
Changes in outbuilding directions and shifts in sediment provenance are key factors for understanding the development of the Cenozoic succession in the central and northern North Sea. By establishing a seismic stratigraphic framework for the Cenozoic succession, and through utilization of velocity data and analyses of sediment compositions, these factors are investigated. Sequence geometries and reflection terminations are identified and related to basin-floor geometry and variations in erosional base level. Mineralogical and geochemical analyses of sediment samples from selected wells are compared with their seismic sequences. Paleogene clastic wedges rich in smectite were built from the East Shetland Platform and probably drained a source area west and northwest of the present North Sea. Outbuilding from southern Norway took place during Late Paleocene-Early Eocene and in Oligocene to mid-Miocene time. In mid-Miocene time outbuilding from the west stopped and subsequently sediments with a high content of feldspar, detrital chlorite and carbonate were deposited from easterly directions in the central and northern North Sea. The seismic velocity of the Cenozoic sediments increases down to a mid-Miocene unconformity, but the velocities of Oligocene and Eocene sediments below are lower and nearly unaffected by burial depth, resulting in a marked velocity inversion. Two tectonic subsidence events, late Eocene-early Oligocene and late Miocene-early Pliocene, have been identified subsequent to general eustatic sea-level lows. These subsidence events cannot be explained by thermal subsidence, and they may have crucial implications for the understanding of hydrocarbon generation, migration and trapping in the Tertiary and deeper stratigraphic levels.
Relationships between sequence stratigraphy, mineralogy and geochemistry in Cenozoic sediments of the northern North Sea
Authors: Thyberg B. I. , Jordt H. , Bjørlykke K. , Faleide J. I. 
Published: April 2008

Abstract

Cuttings of Cenozoic sediments from selected wells in the northern North Sea have been analysed both mineralogically and geochemically, and compared with seismic sequence stratigraphic units. Variations in the composition with respect to clay minerals, feldspars, major elements and selected trace elements have been used to establish changes in the provenance of the Cenozoic sequences. The Eocene sequence consists of a thickness of several hundreds of metres of almost exclusively smectitic clays with high Ni and Zn contents and little or no quartz. This represents a strong input from subaerial volcanism related to the rifting and initial spreading of the Norwegian-Greenland Sea. The Eocene-Oligocene smectitic mudstones have high porosity and low seismic velocity (<2km s
−1
) compared with the underlying Paleocene sediments and overlying Miocene-Pliocene sequences. The Plio cene and Pleistocene mudstones are coarse-grained clays with an immature mineralogy, which compact much more rapidly than the underlying smectitic sediments. The seismic velocity may then reach 2.5–3.0 km s
−1
and thus cause a strong velocity inversion. This sequence is partly glacial and mineralogically immature, but may contain some kaolinite and smectite, which indicate reworking of lower Tertiary and Mesozoic sediments. Our obser vations indicate that sequence boundaries are closely related to tectonic movements and to changes in the sediment supply from adjacent areas. Both mineralogical and geochemical data can be used as additional tools for correlation in Cenozoic sediments in the northern North Sea. The mineralogy of these sediments also determines the rate of compaction and other factors relevant for basin modelling.
Cenozoic tectonic subsidence from 2D depositional simulations of a regional transect in the northern North Sea basin
Authors: Kyrkjebø Rune , Hamborg Martin , Faleide Jan Inge , Jordt Henrik , Christiansson Peter 
Published: April 2008

Abstract
The Cenozoic depositional history along a regional E–W profile across the northern North Sea has been simulated using a forward process-based simulation program of dynamic-slope type. It involves a depth-dependent, dual-lithology diffusion equation that handles transport, erosion and deposition of sediments. The data used in the simulation were derived from a seismic line calibrated against wells, and from the regional literature concerning the northern North Sea. The most important of the factors used are: the initial basin form (Paleocene bathymetry), tectonic subsidence, isostatic variables, sediment supply (sand-shale), sediment compaction (porosity-depth relationships for sand-shale) and eustatic sea-level changes. The interaction between the data values extracted from the literature could not reproduce a cross-section similar to the observed cross-section from seismic data. Therefore, the subsidence pattern and the initial basin form were reconsidered. The resulting model gave an anomalous Cenozoic subsidence pattern, different from the expected post-rift thermal subsidence, with deviations corresponding to Paleocene and Late Miocene-Pliocene times. The model-derived Paleocene subsidence might have been overestimated by using an over-shallow palaeobathymetric value, although a deepening of the basin is also indicated by biostratigraphic data. The pronounced Neogene subsidence created accommodation space for a thick Pliocene sequence, derived from the uplifted eastern source area.
NE Atlantic continental rifting and volcanic margin formation
Authors: Skogseid Jakob , Planke Sverre , Faleide Jan Inge , Pedersen Tom , Eldholm Olav , Neverdal Flemming 
Published: April 2008

AbstractDeep seismic data from the Hatton-Rockall region, the mid-Norway margin and the SW Barents Sea provide images of the crustal structure that make it possible to estimate the relative amounts of crustal thinning for the Late Jurassic-Cretaceous and Maastrichtian-Paleocene NE Atlantic rift episodes. In addition, plate reconstructions illustrate the relative movements between Eurasia and Greenland back to Mid-Jurassic time. The NE Atlantic rift system developed as a result of a series of rift episodes from the Caledonian orogeny to early Tertiary time. The Late Palaeozoic rifting is poorly constrained, particularly with respect to timing. However, rifted basin geometries, inferred to be of this age, are observed at depth in seismic data on the flanks of the younger rift structures. Intra-continental rifting in Late Jurassic-Cretaceous times causedc.50–70 km of crustal extension and subsequent Cretaceous basin subsidence from the Rockall Trough-North Sea areas in the south, to the SW Barents Sea in the north. In late Early to early Late Cretaceous times, new rifting occurred in the Rockall Trough and Labrador Sea associated with the northward propagation of North Atlantic sea-floor spreading. When sea-floor spreading was approached in the Labrador Sea the Rockall rift apparently became extinct. The final NE Atlantic rift episode was initiated near the Campanian-Maastrichtian boundary, lasted until continental separation near the Paleocene-Eocene transition, and causedc.140 km extension. The late syn-rift and the earliest sea-floor spreading periods were affected by widespread igneous activity across ac.300 km wide zone along the rifted plate boundary. The deep seismic data provide lower-crustal structural geometries that represent boundary conditions for a better mapping and understanding of the extensional thinning of the crust. The crustal geometries question extension estimates previously made from basin subsidence analysis, and aid in the definition of bodies of magmatic underplating beneath the outer volcanic margins.
The tectonic evolution of the Norwegian Sea Continental Margin with emphasis on the Vøring and Møre Basins
Authors: Brekke Harald 
Published: April 2008

AbstractThe Norwegian Sea continental margin is dominated by two major basins with a very thick Cretaceous basin fill: the Vøring and Møre Basins. The basins are flanked by the uplifted mainland and the Cretaceous Trøndelag Platform to the east and by the Møre and Vøring Marginal Highs capped by Eocene lavas to the west. The tectonic development of the area is controlled by two structural trends: NE-SW and NW-SE. The area has been tectonically active from Carboniferous to Late Pliocene time with the main tectonic phases in Late Palaeozoic, late Mid-Jurassic-Early Cretaceous and Late Cretaceous-Early Tertiary time. The general tectonic development comprised a long period of extension and rifting that ended in Early Eocene time by continental separation, major volcanism and subsequent sea-floor spreading in the Norwegian-Greenland Sea. In Carboniferous to Early Cretaceous time the extensional tectonics were related to within-plate continental rifting. The tectonics of the Late Cretaceous and the Tertiary periods were controlled by the relative movements along plate boundaries. The overall NE-SW structural grain is constituted by faults and basin axes that probably originated in Late Palaeozoic time and were active during all subsequent tectonic phases. The transverse NW-SE trend is expressed as major lineaments that probably reflect the old, Precambrian grain of the basement. These lineaments, two of which are the continuation into the continental crust of major oceanic fracture zones, controlled the tectonic activity throughout Cretaceous and Tertiary time and constitute the boundaries between the major structural provinces of the area. The differentiation into the Cretaceous basins and the bounding platforms and marginal highs started by the late Mid-Jurassic-Early Cretaceous extensional phase. The subsequent Cretaceous subsidence history, where the basin flanks formed by flexuring rather than faulting, resulted in an exceptionally thick basin fill. In the Vøring Basin the Cretaceous development comprised an early thermal subsidence phase and a post-Cenomanian phase of tectonically driven subsidence involving intermittent phases of normal faulting and compression and folding. The Vøring Basin was tectonically active also during Tertiary time with the main phases of strike-slip-compression coinciding with the Alpine orogenies in Late Eocene and Mid-Miocene time. Within the Vøring Basin there is evidence of the formation of a fossil opal A-opal-CT transition and extensive regional marine erosion in Mid-Miocene and Late Pliocene times. In contrast, the Møre Basin was generally tectonically quiet throughout the Cretaceous and Tertiary periods, experiencing mainly continuous subsidence.
Atlantic volcanic margins: a comparative study
Authors: Eldholm O. , Gladczenko T. P. , Skogseid J. , Planke S. 
Published: April 2008

AbstractVolcanic margins in the Atlantic Ocean reveal a series of common crustal units and structural features developed during continental extension and break-up. We suggest that four main crustal zones can be recognized on volcanic margins. This tectono-magmatic zonation implies a history of development where tectonic and magmatic styles and dimensions depend on the interaction of lithospheric and asthenospheric properties and dynamics. The amount of excess igneous activity depends on the temperature and fluid content of the asthenosphere along the incipient plate boundary and the dynamic history of the lithosphere during the rift phase. An adequate understanding of the margin history requires studies of the entire rift, i.e. the conjugate margins. We also note that the spectacular wedges of seaward-dipping reflectors observed along many rifted margins are only one of many igneous features originating during the process of break-up and initial seafloor spreading. Probably, most passive rifted margins represent intermediate cases relative to the volcanic and non-volcanic end-members. A mantle plume impinging on lithosphere already under extension emplacing Large Igneous Province-type initial oceanic crust, including an extensive extrusive cover, is considered the most likely explanation for volcanic margins. Hydrocarbon resource evaluations of volcanic margins have to include their characteristic tectono-magmatic features and their consequences for vertical motion, erosion, sedimentation, thermal and burial histories, and maturation.
Interlayer slip and joint localization in the East Kaibab Monocline, Utah: field evidence and results from numerical modelling
Authors: Cooke M. L. , Mollema P. N. , Pollard D. D. , Aydin A. 
Published: April 2008

Abstract
The mechanics of deformation in multilayer flexures is analysed by comparing field observations of joint clusters from the East Kaibab Monocline, Utah with fracture patterns produced in analytical and numerical experiments. Dune boundaries (bedding planes) were mapped through the thickness of the aeolian Navajo Formation, and the occurrence of joints related to dune boundary slip and fold curvature was documented. Slip along dune boundaries, as evidenced by joint clusters oblique to bedding, occurs along the steep limb of the fold and in the middle of the Navajo. Joints perpendicular to bedding and parallel to the fold axis occur near the synclinal hinge. Numerical experiments examine a layer flexed to match the Navajo at Hackberry Canyon with both uniform and observed distribution of dune boundaries. Within the numerical experiments, horizontal frictional interfaces slip within the centre of the layers where dips are steepest, and opening-mode fractures related to curvature form within the anticlinal and synclinal hinges of the fold. Thus, the first-order numerical results match field observations. This study illustrates the important roles of mechanical stratigraphy and interlayer slip in multilayered folding and the contribution of bedding-plane faults and fold curvature in the production of joint clusters.
Regional tectonics and fracture patterns in the Fall River Formation (Lower Cretaceous) around the Black Hills foreland uplift, western South Dakota and northeastern Wyoming
Authors: Wicks John L. , Dean Stuart L. , Kulander Byron R. 
Published: April 2008

Abstract
The Fall River Formation around the Black Hills uplift is pervasively fractured by layer-perpendicular joints. Systematic joints in the formation maintain consistent orientations over large areas and are commonly abutted by later-formed fractures, resulting in an orthogonal pattern. There are two major systematic sets, trending northeast and northwest, and one minor set trending north-south. The first two sets define two major fracture domains in the study area. The northwest joint set occupies a southern domain where it is the sole systematic fracture set. The northeast joint set is pervasively established throughout the northern domain, where northwest and north-south fracture sets are also developed in well-defined sectors. There is no genetic or spatial relationship between joint sets and local Laramide monoclines or folds of the region. Instead, the stratigraphic record indicates that joint development originated early in the lithification history of Fall River sandstones. Jointing occurred in response to local and regional extensional stresses that pervaded the northern and southern domains as a result of recurrent movement on basement faults that parallel the regional lineament system and surface structural zones throughout the region. Major uplift of the Black Hills and local fold development during Laramide time merely resulted in passive rotation of the early formed systematic and non-systematic joints.
The evolution of the Main Mantle Thrust in the Western Syntaxis, Northern Pakistan
Authors: Argles T. W. 
Published: April 2008

Abstract

Neogene events in the Nanga Parbat-Haramosh massif have obscured much of its earlier evolution. However, structural mapping of the eastern margin reveals a ductile contact zone preserving many features of the original Main Mantle Thrust that emplaced the Ladakh island arc over the Indian margin in the late Cretaceous. The sequence of ductile deformation was controlled both by the contrasting rheologies of the Ladakh island arc and the Main Mantle Thrust footwall, and the changing thermal regime during subduction, collision and burial. Preliminary
P-T
estimates indicate conditions during southward thrusting on the Main Mantle Thrust of
c.
650 °C and 9.5 kbar, with later deformation (post-dating garnet growth) in some units at
c.
500 °C and 7.4 kbar. The concordant fabrics and lithological boundaries on either side of the contact are only disrupted by a NW-vergent, brittle thrust south of the village of Subsar (Indus gorge) which cross-cuts the steepened Main Mantle Thrust Zone. This thrust is related to the neotectonic Liachar Thrust on the western margin of the massif, and is an expression of the regional tectonics at the western termination of the Himalayan arc. This late thrusting followed formation of the syntaxial antiform in Neogene times.
Unroofing of the Nanga Parbat Himalaya
Authors: Shroder J. F. , Bishop M. P. 
Published: April 2008

Abstract

The rapid erosional unroofing of the Nanga Parbat Himalaya in late Cenozoic time is thought to have been initiated when the Indus River, initially flowing somewhat north and well to the west of its present location, was captured and diverted south close to the massif of today by extensional structures and downfaulted topography across the Kohistan-Ladakh island arc terrane. It is hypothesized that the Nanga Parbat pop-up structure was initiated at
c.
12-10 Ma, as a tectonic aneurysm caused by rapid incision by the Indus River and other surface processes. Because of this subsequent rapid unroofing of the region, however, the oldest sediments to record erosion in the immediate region of Nanga Parbat are < 200 ka old: most sediments and our cosmogenic and ISRL exposure dates are more than five times younger. Diverse field measurements of rates of local incision and areal denudation for mass movement, glacial, river and catastrophic floods for the past
c.
55 ka are highly differential but internally replicative and externally consistent with research indicating long-term, severe denudation. Averaged rates of maximum incision at more than 15 points around the massif are 22 mm ± 11 mm a
−1
. Late Pleistocene surface processes at Nanga Parbat were capable of erosional unroofing of the massif sufficiently vigorous to produce the pronounced relief of today.