bluuebunny/crossref_metadata_2025_split huggingface dataset:
Geology and metamorphic evolution of the Sanbagawa metamorphic belt, Japan
Authors: Banno Shohei , Sakai Chihiro 
Published: September 2007

Summary

The Cretaceous (pre-Japan Sea) Sanbagawa metamorphism affected the Japanese Jurassic complex south of the Median Tectonic Line in the regions now recognized as the Sanbagawa, Mikabu and Chichibu belts. The metamorphic peak (116 Ma) was reached and passed during the tectonic ‘D
1
’ deformation, corresponding to sinistral shear N30°E along the eastern margin of the Asian continent. This was followed by ‘D
2
’ (c. 85 Ma) fold and thrust deformation, the vergence of which is normal to the ‘D
1
’ trend. These deformational events established the present thermal structure. The final regional deformation formed upright ‘D
3
’ folds. The four metamorphic zones based on pelitic assemblages can be enhanced by using basic schists to subdivide the pelitic chlorite zone. Apparent Fe-Mg partition coefficients between chlorite and garnet show an essential regional continuity of metamorphism and that thrust-offsets do not juxtapose elements from different mineral zones. Peak conditions of metamorphism ranging from 250°C and 6 kbars to 600°C and 10 kbars are consistent with simple
P-T-t
loops which progress at higher pressures and return at lower pressures to the surface.
A discussion of alluvial sandstone body characteristics related to variations in marine influence, Middle Jurassic of the Cleveland Basin, UK, and the implications for analogous Brent Group strata in the North Sea Basin
Authors: Alexander Jan 
Published: September 2007

Abstract
The pattern of deposition in the Middle Jurassic Cleveland and North Sea basins was complicated by spatial and temporal variations in the amount of marine influence. These variations ranged from major changes in shore-line position resulting in the alternating deposition of marine and non-marine formations to minor shore-line movements, incursions, tidal back-up, saline wedge intrusion and storm/tide/rain-induced flood events. The fluctuating extent of marine influence resulted from the interplay of factors including sedimentation rate, compaction, local tectonic activity and eustatic variations. The extent of marine influence on the alluvial environment affected the nature and architecture of sandstone bodies and the nature of early diagenesis.
It is probable that within the North Sea area local and regional relative sea-level fluctuations during Ness Formation deposition would have resulted in a range of alluvial sandstone body types similar to those of the Middle Jurassic of Yorkshire seen in outcrop. Major changes in sea-level relative to surface subsidence resulted in changing sandstone body architectural styles, while minor changes in marine influence resulted in significant changes in internal sandstone body characteristics.
Palynological review of the Brent Group, UK sector, north sea
Authors: Whitaker M. F. , Giles M. R. , Cannon S. J. C. 
Published: September 2007

Abstract
A biostratigraphical zonation of the Brent Group, applicable within local oil field areas, has been established. It comprises 11 palynozones and subzones, eight of which are confined to the Ness Formation. Palynomorph associations and palynofacies types are shown to broadly correspond to specific palaeoenvironments. A regional ‘event’ scheme is outlined which establishes chronostratigraphical correlations and suggests temporal relationships between deltaic and delta front sediments. Integrated palynofacies data have allowed the development of deltaic sub-palaeoenvironments and lithofacies to be examined with respect to time and, in this way, to chart the possible progress of the delta as it prograded. Similarly, this approach enables possible areas of concentrated fluvial channel activity to be identified and the likely migration of these fluvial fairways with time. The implications of this depositional model for reservoir development and performance is discussed, showing the varying orientation of the delta front and barrier sands as it changed from a predominantly N-S trend during its early stages to WNW-ESE in its final stages.
Palynology as a palaeoenvironmental indicator in the Brent Group, northern North Sea
Authors: Williams Gwydion 
Published: September 2007

Abstract
The Brent Group of the northern North Sea can be subdivided into a series of 12 assemblage units on the basis of palynomorph and kerogen abundances. These assemblages, which can be identified on a regional basis, have been recognized extensively throughout wells of the Brent Group depositional area. They represent changes in the environment, kerogen source and depositional setting and can be linked to lithostratigraphical units. Changes in assemblages through the Brent Group reflect an initial restricted marine environment followed by progradation in a regressive regime. Progradation ceased and the maximum point of regression occurred within the ‘Mid’ Ness Formation, after which deposition occurred within an abandonment and transgressive regime. These features are defined by palynological data, thus providing input into the regional understanding of Brent Group deposition. The palynological assemblages of the Brent Group are illustrated with reference to two wells: 211/18a-A31 from the Thistle Field and 3/3-5A from the Ninian Field.
Palynomorph assemblages within the Brent Group are largely facies controlled and have an intimate relationship with lithofacies. The identification of these assemblages, therefore, allows for the positive identification of individual lithostratigraphical and reservoir units, particularly in problematic sections where stratigraphical interpretations based on other disciplines are hampered by faulting and truncation or lack of conventional core material and wireline log data, particularly where sidewall core samples are available.
Burial diagenesis of Brent sandstones: a study of Statfjord, Hutton and Lyell fields
Authors: Harris Nicholas B. 
Published: September 2007

Abstract

Brent sandstone compositions vary systematically with increasing depth and temperature in three North Sea fields. At Statfjord field (
c.
2500 m), sandstones are arkoses, lithic arkoses and subarkoses. At Hutton field (
c
. 3050 m), sandstones are subarkoses and quartzarenites, whereas at Lyell field (
c
. 3500 m), sandstones are mostly quartzarenites. Compositions are transformed by pervasive dissolution of plagioclase at relatively shallow depth, dissolution of K-feldspar at greater depth, and alteration of detrital mica to kaolinite or illite. Quartz cement is a minor constituent at Statfjord, mostly forming early during meteoric water flushing. Quartz cement abundance increases significantly at Hutton and particularly at Lyell, where quartz cement comprises up to 130f rock volume; the increase in quartz cement coincides with dissolution of detrital quartz along stylolites and microstylolites at temperatures greater than 90–100°C as well as the dissolution of feldspar.

The dominant clay at Statfjord is kaolinite; at Hutton, illite forms as a pore-lining precipitate and, at Lyell, also by alteration of previously formed kaolinite. The transition from a kaolinite-dominated to an illite-dominated sandstone is probably controlled by several factors, among these the dissolution of K-feldspar, which may be due either to an influx of organic acids from the overlying Heather and Kimmeridge Clay Formations or to thermodynamic instability of the assemblage kaolinite-illite-K-feldspar at temperatures greater than 100°C. Elevated silica activity due to quartz dissolution on styloites and microstylolites may also induce illite formation.
Chemical analysis of sandstone samples shows the Brent undergoes systematic loss of sodium and, to a lesser extent, potassium during burial diagenesis. The sodium loss is consistent with observed plagioclase dissolution. The potassium loss indicates that the potassium in illite is derived from the Brent itself, probably from dissolved K-feldspar, and not from an external source such as a basinal brine.
The petrophysical characteristics of the Brent sandstones
Authors: Moss Brian 
Published: September 2007

Abstract
The commonly occurring ranges and the principal controlling factors of the porosity, permeability, capillary characteristics and fluid saturations of the Brent sandstones are presented. Whilst there is insufficient space to discuss these parameters in specific detail, their variability and the degree to which they are influenced by the geological characteristics of the Brent sandstones is reviewed. The paper shows, through the use of examples, that a thorough understanding of the petrophysical characteristics of a reservoir rock requires the integration of several types of data into a single model. The wireline log and laboratory core analyses provide a quantitative input, whilst geological factors such as mineralogy, diagenetic history, and sedimentary fabric provide a most necessary framework within which the pore geometry variability, detected by log and core data, can be examined. An appendix summarizes the principal quantitative techniques involved.
Opportunities for the development and utilization of coalbed methane in three coal basins in Russia and Ukraine
Authors: Marshall James S. , Pilcher Raymond C. , Bibler Carol J. 
Published: September 2007

Abstract

The coal mining regions of Russia and Ukraine liberate almost 4.5 × 10
9
m
3
of methane annually, of which only 3.9% is being utilized. Preliminary estimates suggest that the methane resources contained in coal mines of the Donetsk, Kuznetsk and L’vov-Volyn basins range from 0.6 to 1.1 × 10
12
m
3
. Various opportunities exist for increasing the quantity and quality of methane recovered from coal mines in these basins. The most attractive options for utilization of this methane include generating heat and power for use at mine facilities and nearby industries or residences.
Nature and origin of fractures in Permian coals from the Bowen Basin, Queensland, Australia
Authors: Pattison C. I. , Fielding C. R. , McWatters R. H. , Hamilton L. H. 
Published: September 2007

Abstract
A field investigation into the development of cleat and other fractures within Permian coal measures was undertaken in the Bowen Basin of eastern Queensland, Australia to provide predictive information on coal permeability for use in coalbed methane exploration. Data were collected from five open-cut and three underground mines in the southern and central Bowen Basin, covering the Upper Permian German Creek Formation and Rangal Coal Measures. Fractures noted in the coals fall readily into the four categories of faults and shear zones, extension and compression-related joint sets, mining-induced fractures and coal cleats. Four geometric varieties of coal cleats were identified: class A orthogonal sets, class B sinusoidal sets, class C polygonal sets and class D chaotic sets. Superimposed or overprinted type A sets were also observed locally. On a regional scale the cleats typically parallel dip (face cleats) and strike (butt cleats), but local departures from this pattern occur in proximity to faults, where face and butt cleat directions were often reversed, rotated or multimodal. Field data suggest that coal cleats of classes A B and C were formed by brittle fracturing of the coal during burial, wheras class D and superimposed cleats were formed during later compressional events. Constraints on the timing of deformation events affecting the Bowen Basin, and geochemical data provided by other workers indicate that the cleats were formed within 5 Ma of formation of precursor peats, but were in many instances modified by later structural events.
Palaeoceanographic information derived from acoustic surveys of glaciated continental margins: examples from eastern Canada
Authors: Syvitski James P. M. , Lewis C. F. Michael , Piper David J. W. , Syvitski James P. M. 
Published: September 2007

Abstract
Much palaeoceanographic information can be gleaned from seismic, sidescan and bathymetric data on glaciated continental shelves. High-resolution seismic reflection surveys of regional ice terminus features define palaeo-ice margins, datable using interfingering ice-proximal glacimarine deposits. Isopach maps show differences in regional accumulation rates of sediments during deglaciation phases and help locate positions of former glacifluvial discharge outlets. Maps of ice-distal glacimarine muds suggest that surface currents carrying buoyant plumes of glacial flour may extend >100 km from an ice margin. Transport and melt of icebergs controlled by circulation of deeper outer shelf and slope currents and episodic storms can result in a glacial influence >1000 km from the ice margin, but most iceberg-rafted sedimentation occurs within a few hundred kilometres of calving. The direction of these palaeo-mid-depth currents may be obtained from statistical analysis of relict iceberg scour patterns and from sediment dispersal patterns. The geometry of glacimarine deposits commonly suggests that there was water column stratification with associated weak near-seafloor currents. Comparison of the shape of glacimarine and post-glacial sediment packages shows that in many places the tidal current intensity has increased through the Holocene, reflecting sea-level change on the shelf.
Rock (mineral)-magnetic properties of post-glacial (16–0.5 ka) sediments from the Emerald Basin (Scotian Shelf), Canada
Authors: Hall Frank R. , Reed Stefanie J. 
Published: September 2007

Abstract
The Emerald Basin is a shallow, ice-scoured marine basin located on the central Scotian Shelf. Rock magnetic analyses were performed on (1) four piston cores (H87003-002, 004 and 006; H88-010-005) extracted from the central portion of the basin, (2) outctrop samples collected from 11 sites on the Nova Scotian mainland and (3) a borehole sample collected from the Gulf of St Lawrence. The results of these analyses show that the rock magnetic data have a consistent pattern throughout the Emerald Basin. In particular, magnetic mineral compositional and grain size parameters show a significant change between about 11 and 10 ka, implying a change in sedimentation patterns associated with the Younger Dryas chronozone. Further, the results of these analyses suggest that the rock magnetic data can be used to differentiate between potential sediment sources from the northwest and southeast sides of the mainland. No evidence of red beds from the northwest of the mainland entering the basin is observed, suggesting that sediments from the Gulf of St Lawrence side of Nova Scotia bypassed the shelf, probably being transported to the deep sea via the Laurentian Channel.
Foraminiferal biostratigraphy of the post-mid-Miocene in the Danish Central Trough, North Sea
Authors: Konradi P. B. 
Published: September 2007

Abstract
The formatiniferal content of ditch cutting samples from three exploration wells in the Danish North Sea has been investigated in the sections above the mid-Miocene marker. The wells are Cleo-1, situated at the edge of the Central Trough, and Kim-1 and M-10 situated in the central part of the trough, in the northern and the southern part, respectively. Based on analysis of the benthic foraminiferal faunas, the strata in the boreholes are subdivided in accordance with the standard North Sea zonation. The interpretations of the faunal assemblages indicate the oldest strata to be deposited in an open marine, outer shelf environment. Up-hole through the wells, the content of planktonic species diminishes gradually; the benthic assemblages indicate shallowing water depth reaching an inner shelf to littoral environment. This is interpreted to reflect the filling of the North Sea Basin through the Middle to Late Miocene when sedimentation mainly occurred in the north. In Early Pliocene the sedimentation centre had shifted to the south whereas in Late Pliocene a hiatus is found in the south and northeast and sedimentation only took place in the northwest in the basin centre. The faunas in the Pleistocene deposits indicate an inner shelf to littoral environment, with periods of reduced salinity and non-marine sedimentation.
Tidal sedimentation in Inner Hebrides half grabens, Scotland: the Mid-Jurassic Bearreraig Sandstone Formation
Authors: Mellere D. , Steel R. J. 
Published: September 2007

Abstract
The Bearreraig Sandstone Formation (Late Toarcian-Bajocian), on the islands of Skye and Raasay, in NW Scotland, forms part of the marine infill of one of the Hebridean rift basins that developed during the early stages of the opening of the North Atlantic. The Formation, up to 250 m thick in south Skye, and from 150 m to 180 m thick in north Skye and Raasay, is a spectacular succession of medium to coarse-grained, tidally generated, cross-bedded sandstones, and subordinate shales. The sandstones sharply overlie the Dun Caan Shales and Raasay Ironstone and are abruptly blanketed by the Garantiana Clay Member.
The succession was deposited under the influence of a series of significant sea-level fluctuations during a 12 Ma interval. During regressive phases of the basin coastline, sedimentation occurred largely at the mouth of a tidal-dominated delta which evolved into a macrotidal estuary during each transgressive phase. Five major facies associations have been recognized: (1) shale/siltstone-dominated successions containing sharply based, strongly bioturbated sandstone beds interpreted as prodelta deposits; (2) medium to coarse sandy successions of thickening-upward, small to very large-scale planar cross-stratified sets, representing dune fields in the tidally dominated delta-front environment; (3) delta-plain, very fine sandstones with roots and fluvial channels; (4) estuarine, tidal channel-fill deposits which overlie erosion surfaces up to 10 m deep and consist of both bioturbated and non-bioturbated, large-scale, tabular or trough cross-bedded medium/coarse sandstones (sets 2–10 m thick) often deformed by water-escape structures and slumping; (5) bioturbated, thinning-upward tabular sandstone beds, interpreted as transgressive shelf deposits.
Palaeocurrent data indicate that during the early stage of deposition of the Bearreraig Formation, tidal-dominated sedimentation occurred separately in the north Skye/Raasay and in the south Skye sub-basins. During a late stage of deposition, the sub-basins merged, and sedimentation occurred uniformly throughout the region. This change in palaeogeographical configuration is associated with a regionally extensive unconformity. Tectonic activity, particularly at an early stage in the form of tilting and block rotation, is believed to have enhanced tidal circulation within the fault-constrained sub-basins.
Nearshore sediment transport processes due to moderate hydrodynamic conditions
Authors: Eitner V. , Kaiser R. , Niemeyer H. D. , Eitner V. 
Published: September 2007

Abstract

On the beach of the island of Norderney sedimentological, morphological and hydrodynamic measurements have been carried out in order to investigate sediment transport processes in the course of a tidal cycle which was characterized by moderate hydrodynamic conditions. Wave heights varied between 0.3 and 0.5 m. An area of 90 m
2
within a groyne field was surveyed. Sediments samples were taken on a 5 m grid at low tide. Sediment flux was determined at each sampling site by means of depth-of-activity rods. The grain size distributions of the sediment samples were determined by dry sieving. Under the prevailing hydrodynamic conditions a landward sediment transport was observed. The mainly negative sediment budget in the seaward section and the landward directed distribution of fluorescent sediment tracers suggest a dominant onshore transport during the investigated tidal cycle. This is also reflected in the changes observed in sediment textures.
An interdisciplinary approach to the evaluation of physical parameters of shallow marine sediments
Authors: Missiaen T. , McGee T. M. , Pearks D. , Ollier G. , Theilen F. 
Published: September 2007

Abstract

A large number of high-resolution seismic investigations and
in situ
geotechnical measurements were carried out in the southern Baltic, offshore Bornholm. The geotechnical measurements, carried out with Ifremer’s Geotechnical Module and Kiel’s GISP system, provided information on cone resistance, induced pore pressure and density of the surficial sediments. The seismic data were subjected to different processing techniques, including detrending and multiple quotient division, which made it possible to deduce the reflection coefficients and impedance contrasts at subbottom interfaces. The different geotechnical and seismic data sets were carefully integrated. There is a good correlation between the
in situ
results and the interpreted seismic units. Strong variations in geotechnical plots correspond with the reflectors identified on processed seismic sections. The general trend of calculated impedances agrees well with the lithological interpretation. However, it would appear that the inversion method does not always result in quantitatively correct values of the sediment parameters. Further development and refining of this method will undoubtedly provide better estimates of the
in situ
bulk properties of the shallow marine sediments.
Lithological and geochemical evidence of Fe and Mn pathways during deposition of Lower Proterozoic banded iron formation in the Krivoy Rog Basin (Ukraine)
Authors: Kulik Dmitri A. , Korzhnev Michael N. 
Published: September 2007

Abstract

Data on stratigraphy, chemical and mineral composition of siliciclastic and ferrugionus rocks of greenschist to epidote-amphibolite metamorphic grade, multi-order cyclicity and banding, isotopic composition of sulphur and carbon and other features of the Krivoy Rog Supergroup metasedimentary rocks are summarized. They provide an insight into the primary sources and the nature of siliciclastic and chemogenic components of banded iron formation (BIF), as well as on pathways of Fe, Mn and Si in the Krivoy Rog palaeobasin at the time of BIF accumulation. Skelevat and Saxagan iron-ore Groups were deposited in a single cyclic transgressive-regressive sequence, probably in a trough-like landlocked basin with complex bottom topography defined by syn-sedimentary faults inherited from the earlier rift structures. Variations in sea level, humidity of climate, continental run-off, oceanic water inflows etc. many times provoked the rapid facies changes ranging from sedimentation of land-derived siliciclastics to deposition of nearly pure chemogenic sediments of the oxide facies BIF in the deeper parts of the basin. Up to seven pairs of schist (
s
-) and BIF (
f
-) horizons were deposited in the Saxagan Group. Lateral variations of their thicknesses, distribution of free carbon in the rocks and other data indicate that only parts of the basin at a given time were optimal for chemical sedimentation; major part of dissolved Fe, Si and Mn was supplied by constant or event inflow of suboxic ocean water.

The Mn content in the Krivoy Rog Supergroup BIFs could serve as an indicator of the fraction of total Fe that precipitated chemically as carbonate. The main part of Fe precipitation in form of Fe(III) hydroxide particles, possibly coated with amorphous silica, is due to a number of oxidation mechanisms operating in the photic surface water layer. On the basis of physicochemical considerations, it is concluded that the Mn CO
3
content in siderite (
c.
2 mol %) contained in the BIF rocks reflects a uniform dissolved Mn concentration (
c.
1 ppm) in the ocean and basin waters. Sedimentation of the typical association of Mg-Fe carbonates and silicates of the carbonate-silicate facies BIF could occur in the near-bottom water only in the case of strong enrichment in dissolved Fe(II) (up to 100–200 ppm) relative to the ocean water (1–10 ppm), which required a stratified brackish-water basin with an estuarine-type circulation. No enrichment in dissolved Mn(II) was possible until
p

O
2

in the atmosphere raised high enough for precipitation of particulate Mn oxide in the photic zone and its dissolution in the suboxic near-bottom waters.