bluuebunny/crossref_metadata_2025_split huggingface dataset:
The continental margin of central East Greenland in relation to North Atlantic plate tectonic evolution
Authors: BOTT M. H. P. 
Published: December 2007

The East Greenland continental margin is inferred to have formed in three stages during the Tertiary evolution of the adjacent North Atlantic Ocean. The East Greenland basaltic volcanism occurred over a period of 2–3 Ma, which was just prior to the probable date of onset of seafloor spreading in the Early Eocene shortly before magnetic anomaly 24B (52 Ma). The associated coastal flexure is interpreted as marking the edge of a zone of stretched and thinned continental crust beneath the inner Denmark Strait shelf and Jan Mayen microcontinent; this represents a short-lived rifting phase just prior to break-up. According to the evolutionary model, the initial break-up produced the margins south of the Faeroe Transform Fault (68.5°N) and north of the Jan Mayen Fracture Zone (72°N), but in the intervening region the microcontinent remained attached to East Greenland. After break-up, the outer shelf of Denmark Strait formed from anomalously thick oceanic crust complementary to the Iceland-Faeroe Ridge. The Blosseville Kyst margin (68.5°N to 70°N) was initiated after anomaly 20 time (42 Ma) as the Jan Mayen microcontinent started to separate from Greenland with spreading on both sides. The new split occupied the line of the pre-existing coastal dyke swarm and flexure. The Liverpool Land margin (70°N to 72°N) was also initiated at this time, but the main separation of the northern part of the microcontinent only commenced after anomaly 7 time (26 Ma) when a single spreading axis was relocated west of the microcontinent.
It is suggested that the Blosseville lavas subsided during deposition by loading and slight crustal stretching. Doming occurred near Kangerdlugssuaq at the time of break-up. Otherwise the topography of the lavas remained subdued until the relocation of the spreading axis at 26 Ma, after which the main regional uplift took place.
The origin of late spar cements in the Lincolnshire Limestone, Jurassic of central England
Authors: EMERY D. , HUDSON J. D. , MARSHALL J. D. , DICKSON J. A. D. 
Published: December 2007

The carbon and oxygen isotopic compositions of the Lincolnshire Limestone (Bajocian) of the East Midlands are shown to be determined largely by two end-member components: marine precipitates and later sparry burial cements. The origin of major quantities of such burial cement is controversial, the extreme possibilities ranging from calcite precipitation from meteoric groundwaters to precipitation from highly saline brines, with contrasting flow regimes.
This study demonstrates how formation-wide sampling and mapping of stable isotopic compositions of burial cements from the Lincolnshire Limestone, combined with a detailed knowledge of its burial history and associated thermal evolution, can be employed to distinguish the influence of different water types. Two 'Provinces' are differentiated with respect to the stable isotopic compositions of the latest, volumetrically most significant, ferroan burial cements.

(1) A 'Southern Province' associated with thinning of the Limestone, shallower depths of maximum burial (approx. 300 m) and light δ
18
O and δ
I3
C cement compositions;

(2) A 'Central Province' associated with deeper burial (approx. 550 m) but less
18
O- and
13
C-depleted cement compositions.

The relative isotopic depletion of the Southern Province ferroan burial cements is considered to be a function of their precipitation from meteoric waters, with a depleted
I8
O signature relative to seawater, at temperatures of approximately 24 °C.
13
C depletion is tentatively ascribed to the persistence of
13
C depleted soil-gas CO
2
in the precipitating waters.

In the Central Province, basinal waters of both meteoric and marine derivation are considered to have precipitated the late spar, with associated up-dip fluid movement at temperatures between 29 and 39 °C.
13
C depletion is believed to be controlled by the input of CO
2
derived from thermal oxidation of organic matter.
Strike-slip faulting along the Church Stretton Lineament, Old Radnor Inlier, Wales
Authors: WOODCOCK N. H. 
Published: December 2007

The Old Radnor Inlier comprises Precambrian sediments unconformably overlain by Wenlock age limestones and shales. Its structure is dominated by steep strike-slip faults. Major NE-SW faults probably bound the inlier and are linked by more northerly faults to form a strike-slip duplex. Strike-slip faults within the inlier match a Riedel shear system, with observed dextral offsets on a NW striking set and implied sinistral offsets on the major inlier-parallel faults. Subordinate dip-slip faults are anomalously oriented, but may be Riedel shears reactivated during progressive sinistral transtension across the inlier.
Pre-Wenlock deformation is recorded by the tilting of the Precambrian sediments and by some faults that do not cut the unconformity. On regional grounds, this deformation might be Ashgill (late Ordovician) or late Precambrian-early Cambrian in age. The strike-slip component now predominating was imposed in post-Wenlock time, probably during the regional sinistral transpression of the Acadian (Late Caledonian) event in Early Devonian time. Later Variscan and Mesozoic components cannot be ruled out.
The detection and illustration of regular sedimentary cycles using Walsh power spectra and filtering, with examples from the Lias of Switzerland
Authors: WEEDON GRAHAM P. 
Published: December 2007

Power-spectral analysis provides an objective method for the detection of regular cyclicity in data recording some oscillating parameter (or time series). Digitization of measured stratigraphic sections is a convenient method for generating long time series, during the examination of pelagic sequences for cyclicity related to orbital variations or Milankovitch cycles. The application of Walsh power-spectral analysis to stratigraphic sections is outlined and band-pass filtering using the Walsh transform introduced. It is shown that variations in sedimentation rate, hiatuses, bioturbation and variations in compaction have the effect of damping or destroying spectral peaks. The wavelength ratios of spectral peaks are often used, during studies of Milankovitch cycles, to decide which orbital cycles are involved. However, in some circumstances hiatuses are able to alter wavelength ratios.
Averaged Walsh power spectra were generated for three Liassic limestone/shale sequences from Breggia Gorge, Switzerland. The 21 000 year (21 ka) precession cycle was detected in all three cases, the 100 ka eccentricity cycle in two cases and the 41 ka obliquity cycle in one. Filtering revealed that the supposed 21 ka sedimentary cycles are grouped into packets of four or five small and large amplitude cycles. The packets reflect the 100 ka modulation of the 21 ka precession cycle. Local disruption of the packaging can be used to locate hiatuses in pelagic strata.
Biota and palaeoatmospheres
Authors: CHALONER W. G. , COCKS L. R. M. 
Published: December 2007

A meeting on Biota and palaeoatrnospheres was held at the Geological Society’s apartmenfs at Burlington House on
19
December
1987.
It was a joint Ordinary Meeting with the Linnean Society and the Palaeontological Association.

This symposium formed part of the celebrations of the Linnean Societ of London, and was held on the eve of its bicentenary year of 1988. The Linnean Society had elected to hold a series of joint meetings with other Societies with allied or overlapping interests, and the Geological Society was an obvious choice. The two societies have been linked physically, by occupying adjoining premises in Burlington House, but more importantly by shared Fellowship, from the earliest days of their co-existence in the present rooms. The principal common ground of the two Societies lies largely in palaeontology and so it was appropriate that plans for a joint meeting should also have involved the Palaeontological Association, which in turn shares membership with both the Geological Society and the Linnean Society. It was, in this way, that the three bodies came to convene a symposium which was to reflect some aspect of their common interests. The organizers decided to try to avoid any of the aspects of conventional palaeontology, but rather sought out a topic which would bring together biologists and geologists on less well-worn ground.
The theme of the interaction of the atmosphere and biota through time was chosen as one which fulfilled this aim, but one which was also topical. The recently initiated International Geosphere–Biosphere Programme has
Alluvial fans and their tectonic controls
Authors: NORTH C. P. , TODD S. P. , TURNER J. P. 
Published: December 2007

The study of alluvial fan sequences, the most proximal components of the alluvial spectrum, can be one of the most profitable avenues of research in basin analysis because fans are particularly sensitive to external influences and have a relatively high preservation potential. Tectonism has long been invoked to explain many variations in fan sediments, and increasingly the presence and nature of fan sequences in the rock record is being used to denote proximity to active faults and to document movement on these faults.
There are, however, many difficulties involved with the interpretation of alluvial fan sequences, not the least of which is deciding whether the sediments are truly components of an alluvial fan or the products of a different depositional system such as an alluvial braidplain. Many of the problems arise from a lack of knowledge about the relative roles in fan construction of allocyclic processes such as climatic change and tectonic activity, and of autocyclic processes such as channel avulsion and fanhead entrenchment.
Whilst researching alluvial fan sediments in a variety of tectonic settings and ages, it has become increasingly clear to the authors that there are many inadequacies in our understanding of alluvial fans, and hence weaknesses in the conclusions drawn from these sediments. This prompted the one-day meeting organized to promote discussion of the problems of distinguishing tectonic from other influences on the evolution of modern and ancient fans. 110 industrial and academic geologists gathered at the University of Bristol on 17th October 1987 to hear 16
Short Paper: Palynomorphs from deformed low-grade metamorphic rocks: an SEM-based technique
Authors: DEAN ANDREW 
Published: December 2007

Scanning electron microscope (SEM) techniques show that the low-grade metamorphic rocks of Southwest England can yield abundant palynomorphs. The technique is outlined and the character of the material illustrated by new assemblages including
Emphanisporites, Dibolisporites
and
Leiotriletes
from the Lower Devonian Meadfoot Group, south Devon.

Progress in the resolution of many problems in the Variscides has been inhibited by lack of site-specific biostratigraphic control. Conventional biostratigraphic techniques have largely failed, particularly for clastic Upper Palaeozoic sequences at low metamorphic grades. However, the application of routine SEM methods has shown that many such rocks may yield palynomorphs. The technique has been applied with considerable success to material from Devonian clastic sequences in Southwest England in a joint programme of research between the University of Exeter and the British Geological Survey, associated with the Cornwall and South Devon Project.
From more than 100 samples routinely collected during the BGS mapping of poorly dated sequences in south Devon (Fig. 1) almost all have yielded some information and many contain well preserved palynomorphs. A local SEM-based biostratigraphy is being formulated for these previously intractable successions. This paper outlines the technique and demonstrates the character of the palynomorph assemblages recovered from a sequence of cleaved interbedded sandstones and mudstones of the Lower Devonian Meadfoot Group, which has generally been considered to be of marine origin.

Method and material.
Field samples are prepared following routine palynological procedures (see Playford & Dring 1981) but omitting the oxidation techniques usually employed. The resultant fraction, after centrifuging, is strew
Tectono-stratigraphic model for the Massif D'Igountze–Mendibelza, western Pyrenees
Authors: JOHNSON JEFFREY A. , HALL CLARENCE A. 
Published: December 2007

The Massif d'Igountze–Mendibelza, western Pyrenees, is a fault-bounded block of Palaeozoic basement overlain by an exceptionally thick Cretaceous siliciclastic sequence. North of the Massif, the Cretaceous sequence conformably overlies Lower Cretaceous carbonates, yet, immediately south of the Massif, it is entirely absent. The sequence fines northward and has NNE palaeotransport. The basement is commonly brecciated near the contact with the sedimentary cover, and the uppermost beds dip less steeply than the lowermost. These tectono-stratigraphic relationships are best explained by Cretaceous deposition above a relatively low-angle normal fault.
The Cretaceous deposits of the Massif d'Igountze–Mendibelza are part of the western extension of the North Pyrenean basin, a basin or series of sub-basins that began to form in the latest Aptian to Albian north of and along most of the length of the North Pyrenean fault. The precise relationship between deposition on the Massif and in the rest of the North Pyrenean basin is not known. There may have been many local variations in stress regime and structural style along the basin or sub-basins, but the regional episode of basin formation was a result of the same plate-reorganizational event. Later basin inversion was due to the latest Cretaceous to Eocene Pyrenean orogeny.
Provenance of Lower Old Red Sandstone conglomerates, SE Kincardineshire: evidence for the timing of Caledonian terrane accretion in central Scotland
Authors: HAUGHTON P. D. W. , ROGERS G. , HALLIDAY A. N. 
Published: December 2007

Northerly-derived conglomerates dominate much of the thick Lower Old Red Sandstone (ORS) succession of the NE Midland Valley of Scotland. These contain a diverse suite of granitoid boulders, the provenance of which can be used to constrain the timing of the post-Caradoc displacements which juxtaposed the Highland Border Complex against the Grampian terrane.
Rb-Sr muscovite-whole rock ages for two-mica granite boulders from the Crawton Group are 473–457 Ma, confirming the persistence of an Ordovician two-mica granite source first recognized in the Dunnottar Group. The Rb-Sr muscovite ages are supported by a U-Pb age of 475 ± 5 Ma for monazite separated from one of the clasts. A Rb-Sr biotite age of 412 ± 4 Ma for a clast of porphyritic biotite granite and geochemical evidence linking this clast to many of the other biotite granite clasts, suggests that late Silurian granitoids and related hypabyssal intrusions have also made an important, hitherto unrecognized, contribution to the conglomerates. Mica-whole rock ages for accompanying psammitic clasts suggest the source included metamorphic rocks (of up to at least staurolite grade) whose uplift overlapped with the intrusion of crustally-derived melts.
The chemistry, chronology and Sr and Nd isotopic compositions of the various igneous clasts are shown to resemble closely the Ordovician through to Silurian magmatic history of a small area of the Grampian terrane in NE Scotland. This is taken as strong evidence for a pre-Lower ORS juxtaposition of the Highland Border Complex and the Grampian terrane, to within several tens of kilometres of their present position. Ashgill–Silurian terrane displacements are invoked to achieve this. Discrepancies in the proportions and types of clast occurring in the conglomerates are explained by: uplift and unroofing of the Grampian terrane prior to docking; the involvement of polycyclic sediment, perhaps as a local veneer of pre-existing sediment on the Grampian terrane; and the likelihood that the source involved parts of the local Grampian terrane which are no longer exposed.
Granite magmas: their sources, initiation and consequences of emplacement
Authors: LEAKE BERNARD ELGEY 
Published: December 2007

Geochemical and other evidence shows that granite magmas are generally derived from a mixture of melted crust and mantle material and the existence of a spectrum of types varying from largely mantle-derived to mainly crustal-derived is emphasized. Each pluton possesses a unique mix or range of mixtures which preserves an adumbrate history of the deeper levels of the crust and mantle at the particular location. Four illustrative granite-forming provinces are considered: (1) Archaean cratons with their voluminous tonalites, (2) magmatic arcs as exemplified by the western Americas, (3) the British Tertiary Province as an example of the results of extensional faulting and (4) the British and Irish Caledonide granites, the main phase (440–390 Ma) of which was produced during major Acadian strike-slip faulting. All these granites provide evidence of mixing of source materials. Geochemistry, especially of the Rare Earth Elements, U-Pb ages and isotopic studies of Sr, Nd, Pb, O, H and in some volcanic rocks Be, is beginning to enable quantification of the source components. The importance of major fracturing of the crust and mantle in providing magma triggers, magma focusses and magma consolidation sites is stressed; major batholiths probably occupy holes created by pulling apart the crust.
Geophysical evidence does not suggest that granite plutons are distributed throughout the thickness of the crust, but rather that they are concentrated relatively near the surface. The extant elevation of the whole of the north British crust, its altitude over the last 400 Ma and even in places the present shape of the coastline, are significantly influenced by Caledonian granites, the tops of which are generally within about 3 km of the present landsurface. Thus relatively little erosion of most of these bodies has taken place and the dominant sources of post-Silurian clastic sediments in the area were stripped off volcanic cover rocks and recycled sediments and metasediments. By inference, other continental areas with numerous exposed granite pluton roofs had a similar history.
The process of granite formation is an important means of density-stabilization of the crust with high-level emplacement of light sialic granite refined out of the mantle and lower, middle and even upper crust. The refractory mafic residues generally become denser and sink or stay down in the density-stratified crust but the division into residue and magma is not sharp with some granite magmas including significant quantites of restite.
An estuarine facies model for the Middle Jurassic Sleipner Formation: Beryl Embayment, North Sea
Authors: RICHARDS P. C. 
Published: December 2007

The Middle Jurassic Sleipner Formation is sub-divided into three units in the Beryl Embayment area of the North Sea. The lowermost two units, the 'Interbedded Unit' and 'Lower Coal Marker', overlie Lower Jurassic marine silts and were probably deposited in progressively shallowing, coastal environments during a eustatic sea level fall. An estuarine deposit overlies the 'Lower Coal Marker', and was deposited following sea level rise or tectonic subsidence of the area. The 'Estuarine Succession' forms the bulk of the Formation, and is composed of seven facies, grouped into three facies associations representing sub-tidal, inter-tidal and salt marsh sub-environments.
The sub-tidal facies association is dominated by sandstones deposited in tidal channels and sand flats. The inter-tidal association is characterized by alternations of sandstone and siltstone on a scale of millimetres to several metres and consists of tidal channel sandstones, lenticular bedded siltstones and other tidally-influenced facies. The salt marsh association is dominated by coals and rooted siltstones, with minor amounts of creek-fill sandstones.
The estuary mouth probably lay towards the northern end of the Embayment, where a connection existed through the Viking Graben to the Boreal Ocean.
A Miocene Gilbert-type fan-delta from a volcanically influenced lacustrine basin, Rusinga Island, Lake Victoria, Kenya
Authors: BESTLAND E. A. 
Published: December 2007

A lacustrine, volcanically influenced fan-delta is recognized in the Kulu Formation of the Miocene Rusinga Group in western Kenya. In the Nyamsingula Gully area on Rusinga Island in Lake Victoria, mapped lithologic units include the classic topset, foreset (mega-foreset) and bottomset structure of a Gilbert-type delta. A distinctive mega-breccia unit of colluvial origin interfingers laterally with the delta deposits and consists of pyroclastic and sedimentary rock fragments derived from underlying and laterally adjacent strata. The breccia formed from the bevelling of a fault escarpment, from which the fan-delta also originated. Away from the fan-delta axis, slumping of fault-scarp colluvium into the lake produced matrix-supported debris flows that are interbedded with lacustrine shales. In the topset beds of the delta, clasts of a distinctive melilitite–nephelinite tuff of airfall origin can be identified and traced down a palaeoslope through laterally adjacent units from the original bedded tuff, into the mega-breccia unit, and finally into debris-flow deposits in the foreset and bottomset beds. During resedimentation the tuff behaved in a brittle fashion due to quick cementation as a result of its water soluble, ultra-alkaline composition.
The Kulu Formation is a distinctive facies that interfingers with the lowermost Hiwegi Formation. Both formations are part of the Rusinga Group. The bulk of the Rusinga Group, excluding the Kulu Formation, represents braidplains and alluvial aprons that flanked the Miocene volcano of Kisingiri. The braidplain and alluvial apron deposits have primary dips away from the volcano and were derived from material erupted and eroded from the volcano. The Kulu Formation, in contrast, was deposited in two small, elongate lacustrine basins separated by a small horst (approximately 5 km long and 2–3 km wide), from which the deposits were largely derived. The fan-delta systems prograded symmetrically away from the horst margins, into the adjoining lacustrine basins. The long dimensions of the horst and lake basins roughly parallel the local slope of the Kisingiri volcano, and therefore deposition in the Kulu Formation was perpendicular to deposition of the other Rusinga Group formations in the vicinity