Observations of coal cleat in British coalfields

This technical report presents the observations made during a study into cleat and joint directions, largely in the Pennine Basin. Field work was carried out under the BGS Research and Development programme in 199 1 - 1992. Interpretation of these observations will be made elsewhere. Cleat is the term widely in use to describe joints in coals. It is generally developed perpendicular to the bedding and there is normally one dominant set, known as the main cleat and a subsidiary, more or less perpendicular, set known as the back or butt cleat. Other sets may be developed in places, particularly in strongly faulted areas (see Figures 1, 2 and 3). Cleat is developed in all bright coals, including coalified allochthonous plant fragments and reworked clasts

The geology and geophysics of the United Arab Emirates. Volume 7, geology of the salt domes of the United Arab Emirates

This report documents the geology of seven of the nine emergent salt domes of the UAE exposed on Delma, Sir Bani Yas, Arzana, Qarnain, Zirku and Sir Bu N’air Islands, along with the only on-land salt dome cropping out at Jebal Dhanna, near Ruwais. Fieldwork for the study took place during field seasons 5, 6 and 7 of the main BGS UAE Regional Geological Mapping program (October to December 2010, January to March 2011 and October 2011). In all cases only a short period of time (4 man days or less) was spent on the islands. Some 400 observation points were made in total. All the major rock types were sampled so that petrographic, XRD and U-Pb zircon analyses could be carried out on selected units. Geological maps at 1: 25 000 scale of each salt dome are given. The salt domes range from about 1 km across (the incomplete remnant of Qarnain) to over 6 km across (Delma). They give rise to dissected hilly topography rising to 140 m above sea-level (Zirku), typically drained by radial wadi systems. The majority of the salt domes are single intrusions, but two domes (Delma and Jebal Dhanna) are multiple-phase diapirs. The rocks of the salt domes belong to the Hormuz Complex, which has been subdivided into the informal Hormuz breccia, the principal rock-type and its suite of entrained exotic clasts. The breccia is made up of soft, altered, clay-rich, vari-coloured gypsum-anhydrite-rich matrix, in which are set sub-angular clasts of all sizes from the mm-scale up to megaclasts several hundreds of metres across. The Hormuz breccia is extremely heterogeneous in terms of colour, grain size, alteration, mineralogy, internal structure, fabric and clast content. The heterogeneity is reflected in the landscape: rounded, deeply eroded, hilly, multi-hued ground, with the larger resistant clasts often forming upstanding blocks and the highest hills. The breccia may be massive or, particularly at the margins, strongly layered, with the layering tending to dip centripetally away from the core. The largest clasts within the breccia are subdivided according to their lithology into igneous megaclasts (mainly volcanic rocks: basalt, rhyolite, dacite, quartz porphyry; some gabbro/dolerite) and sedimentary megaclasts (bedded limestone, dolomite and calcareous shale/siltstone, sandstone, sedimentary breccia, rare metasedimentary rocks). The only other unit mapped comprises the extensive turbidites which form a semi-continuous carapace on Zirku island, termed the Zirku Formation. The original halite of the breccia matrix has largely been dissolved and replaced by anhydrite-gypsum, carbonate, iron and manganese oxides and various clays and micas. U-Pb dating of volcanic igneous rocks shows them to be Neoproterozoic (Ediacaran) in age at c.560 Ma. The maximum age of the Zirku Formation is c.560 Ma as determined by detrital zircon dating, with a layered marble clast from Delma giving an older maximum depositional age of c.590 Ma. Both detrital spectra show a range of older sources from Neo- to Palaeoproterozoic and Archaean in age. The salt domes were emplaced penecontemporaneously with the Miocene country rocks of the Shuwaihat Formation. The latter are often quite strongly deformed immediately adjacent to the diapirs margins (tilted and faulted), but locally also contain Hormuz breccia-derived gravel beds and lenses. Locally, large disoriented blocks of Shuwaihat Formation are found within the salt domes, suggesting that the Miocene rocks once covered the domes and foundered within the roof zone due to salt dissolution in the underlying Hormuz Complex. The salt domes are locally overlain by remnants of Quaternary cover rocks, typically represented by cream-coloured marine clastic carbonate grainstones and interlayered proximal alluvial fan gravels (derived from the Hormuz breccia) of the Jebal Dhanna Formation. These deposits are unique to the salt domes. The salt domes are capped to a greater or lesser extent by an irregular crust, 1 to 3 m thick, of scoriaceous coarsely crystalline brown gypcrete. Evidence of localised relatively recent halokinetic reactivation in small dome-like ‘Salt blisters’, typically a few hundreds of metres across are described from a number of salt islands

A geological basis for land-use planning: Garforth-Castleford-Pontefract : 1:10000 sheets SE42NW, NE, SW, SE, SE43SW and SE52SW, parts of 1:50000 geological sheets 70 (Leeds) and 78 (Wakefield)

This report describes a stuodfy t he Garforth- Castleford - Pontefract areac ommissioned by the Departmenot of the Environment and jointly funded by the Department and the British Geological Survey. The aims of the study were to compile and collate a geological database, and to present threes ults in terms of their application to land use planning and development as a foundation for: a. land-use planning for development and b. safeguarding of mineral resources, and c. effective future geological researc

Geology of the Tarif 1:100 000 map sheet, 100-20, United Arab Emirates

This Sheet Description describes the Quaternary and solid geology of the Tarif 1:100 000 scale geological map. The Tarif district includes the northern coast of the UAE between the outskirts of Mirfa in the west and a point about 23 km west of the settlement of Tarif. The onshore part of the sheet extends a maximum of about 11.5 km south from the coast and is traversed by the main coastal road. The entire island of Abu Al Abyadh lies within the district, separated from the mainland by up to 5 km of intertidal flats and a narrow, dredged channel about 250 m wide across which a roll-on roll-off ferry provides vehicular access. The oldest rocks, of Miocene age, crop out in a series of mesas rising above the coastal plain in the south of the district. These consist of the Dam Formation, overlain by the Shuwaihat Formation, which is largely aeolian in origin, and the Baynunah Formation which includes aeolian and fluvial sediments. The onshore area is a coastal plain dominated by sabkha flats less than 2 m above sea level developed on deflated cemented dune sands of Quaternary age. The northern-most 3–4 kilometres of this flat coastal plane comprise a series of sand sheets forming shallow beach ridges, ‘washover terraces’ and fans with patchy sabkha development. Southwards, the sand sheets pass into an 8–10 kilometre wide zone of low-lying, active sabkha. This zone forms part of a classic, world famous, example of a sabkha and coastal plain and has been extensively studied from both an ecological and geological perspective. In this district much of it has been disturbed by digging and reclamation. Mesas, generally elongated north-west to south-east because of deflation by the prevailing north westerly Shamal wind, stand up to 25 m above the flats and on the rising ground at the southern limits of the sabkha flats. These are outliers of a former continuous cover of Miocene sand-dominated sequences, including the Shuwaihat and Baynunah formations. Abu Al Abyadh Island is one of a number of barrier islands that extend from north of Abu Dhabi to Marawah Island, west of the present area. The inlet between the island and the mainland is the eastern part of an open lagoon known as the Khor Al Bazam. In common with other barrier islands, it has a core of Pleistocene aeolian dune sand around which a series of carbonate sand ridges and bars of Holocene age were accreted. These have been deflated in large areas to less than 2 m above sea-level leading to local sabkha development. The island is generally flat but punctuated by small mesas, known locally as zeugen, forming mushroom-shaped outcrops rising up to 4 m and capped with thin marine limestones attributed to the Fuwayrit Formation of late Pleistocene age. Offshore to the north of the island, below low water, is an area of reefs and coral algal sands called the Great Pearl Bank, on account of the former pearling industry in the region

Guiding the Way to Gamma-Ray Sources: X-ray Studies of Supernova Remnants

Supernova remnants have long been suggested as a class of potential counterparts to unidentified gamma-ray sources. The mechanisms by which such gamma-rays can arise may include emission from a pulsar associated with a remnant, or a variety of processes associated with energetic particles accelerated by the SNR shock. Imaging and spectral observations in the X-ray band can be used to identify properties of the remnants that lead to gamma-ray emission, including the presence of pulsar-driven nebulae, nonthermal X-ray emission from the SNR shells, and the interaction of SNRs with dense surrounding material.Comment: 16 pages, 11 figures, To appear in the proceedings of the workshop: "The Nature of the Unidentified Galactic Gamma-Ray Sources" held at INAOE, Mexico, October 2000, (A.Carraminana, O. Reiner and D. Thompson, eds.

Particle Acceleration in Cosmic Sites - Astrophysics Issues in our Understanding of Cosmic Rays

Laboratory experiments to explore plasma conditions and stimulated particle acceleration can illuminate aspects of the cosmic particle acceleration process. Here we discuss the cosmic-ray candidate source object variety, and what has been learned about their particle-acceleration characteristics. We identify open issues as discussed among astrophysicists. -- The cosmic ray differential intensity spectrum is a rather smooth power-law spectrum, with two kinks at the "knee" (~10^15 eV) and at the "ankle" (~3 10^18 eV). It is unclear if these kinks are related to boundaries between different dominating sources, or rather related to characteristics of cosmic-ray propagation. We believe that Galactic sources dominate up to 10^17 eV or even above, and the extragalactic origin of cosmic rays at highest energies merges rather smoothly with Galactic contributions throughout the 10^15--10^18 eV range. Pulsars and supernova remnants are among the prime candidates for Galactic cosmic-ray production, while nuclei of active galaxies are considered best candidates to produce ultrahigh-energy cosmic rays of extragalactic origin. Acceleration processes are related to shocks from violent ejections of matter from energetic sources such as supernova explosions or matter accretion onto black holes. Details of such acceleration are difficult, as relativistic particles modify the structure of the shock, and simple approximations or perturbation calculations are unsatisfactory. This is where laboratory plasma experiments are expected to contribute, to enlighten the non-linear processes which occur under such conditions.Comment: accepted for publication in EPJD, topical issue on Fundamental physics and ultra-high laser fields. From review talk at "Extreme Light Infrastructure" workshop, Sep 2008. Version-2 May 2009: adjust some wordings and references at EPJD proofs stag

Magnetic fields in cosmic particle acceleration sources

We review here some magnetic phenomena in astrophysical particle accelerators associated with collisionless shocks in supernova remnants, radio galaxies and clusters of galaxies. A specific feature is that the accelerated particles can play an important role in magnetic field evolution in the objects. We discuss a number of CR-driven, magnetic field amplification processes that are likely to operate when diffusive shock acceleration (DSA) becomes efficient and nonlinear. The turbulent magnetic fields produced by these processes determine the maximum energies of accelerated particles and result in specific features in the observed photon radiation of the sources. Equally important, magnetic field amplification by the CR currents and pressure anisotropies may affect the shocked gas temperatures and compression, both in the shock precursor and in the downstream flow, if the shock is an efficient CR accelerator. Strong fluctuations of the magnetic field on scales above the radiation formation length in the shock vicinity result in intermittent structures observable in synchrotron emission images. Resonant and non-resonant CR streaming instabilities in the shock precursor can generate mesoscale magnetic fields with scale-sizes comparable to supernova remnants and even superbubbles. This opens the possibility that magnetic fields in the earliest galaxies were produced by the first generation Population III supernova remnants and by clustered supernovae in star forming regions.Comment: 30 pages, Space Science Review

The Geology and Geophysics of the United Arab Emirates. Volume 6, Geology of the western and central United Arab Emirates

This volume forms part of the product of a multidisciplinary study by the British Geological Survey (BGS), commissioned by the UAE Federal Government, Ministry of Energy, to produce 1:100 000 scale geological maps of the bedrock and superficial geology of the central and western part of the UAE. 1:50 000 scale maps were produced of selected areas near Abu Dhabi and for seven emergent salt domes (mainly on offshore islands). This document therefore follows on from the previous volume (Styles et al., 2006) on the geology of the northern Emirates. The present volume similarly contains information about the findings of the geological mapping and associated specialist research. Much of the central and western part of the UAE is blanketed by Quaternary and recent dune sands, fluvial sediments and sabkhas. The only significant areas of exposed older rocks occur along the coast between Abu Dhabi and As Sila and on the various salt islands. Previous geological maps were made more than 20 years ago and were based largely on air photo interpretation with limited ground-truthing. The rapid economic development in the intervening period has seen a tremendous expansion of the national infrastructure and this has greatly increased the demand for high quality, field-based geological maps. The area was mapped at a scale of 1:50 000 and maps produced at 1:100 000, with the exception of the salt dome islands which were mapped at 1:25 000 scale. An area of the coast around Abu Dhabi is illustrated in two additional maps produced at 1:50 000 scale. Each 1:100 000 scale map is accompanied by a Sheet Explanation that describes the rock sequences in the area covered by that particular map. This report describes the broader features of the main rock groups on a regional basis and includes the results of the specialist laboratory studies that were used to define and interpret the geology of the project area. The field mapping was undertaken in the winter months between October 2008 and March 2011. The mapping was carried out by A R Farrant, R A Ellison, R J Thomas, J W Merritt, S J Price, A J Newell, J Merritt, J R Lee, A B Leslie, H F Burke, R A Smith, K M Goodenough, A Finlayson, C J Jordan and S L B Arkley. The laboratory studies were mostly carried out at the BGS. The petrographic study of the Miocene and Quaternary rocks and sediments was carried out by E R Phillips, whilst the igneous petrology of the Hormuz Complex rocks was undertaken by members of the mapping team. I P Wilkinson undertook micropalaeontologial determinations of both Miocene and recent sediments. The macropalaeontology of the basal Baynunah Formation is based largely on published information provided by Dr Mark Beech, Professor Andrew Hill and Dr Faisal Bibi. Some additional data on the Fars Group was provided by M A Woods. R Knox did the heavy mineral analyses, whilst D Wagner and S Kemp worked on the XRD analysis. The U-Pb zircon and carbonate geochronology was undertaken by M Horstwood, N Roberts and R Parrish at the NERC Isotope Geoscience Laboratories at the BGS, Keyworth. The Optically Stimulated Luminescence (OSL) dating was carried out by Professor G Duller and Dr H Roberts in the Aberystwyth Luminescence Research Laboratory at the Institute of Geography and Earth Sciences, Aberystwyth University. P Turner and C Simpson were responsible for the GIS systems and map layouts. H Holbrook and S Ward drew the majority of the illustrations. W Masterson and A Hill formatted this Memoir and the Sheet Explanations. This volume was compiled by A R Farrant and edited by R J Thomas

Supernova Interaction with a Circumstellar Medium

The explosion of a core collapse supernova drives a powerful shock front into the wind from the progenitor star. A layer of shocked circumstellar gas and ejecta develops that is subject to hydrodynamic instabilities. The hot gas can be observed directly by its X-ray emission, some of which is absorbed and re-radiated at lower frequencies by the ejecta and the circumstellar gas. Synchrotron radiation from relativistic electrons accelerated at the shock fronts provides information on the mass loss density if free-free absorption dominates at early times or the size of the emitting region if synchrotron self-absorption dominates. Analysis of the interaction leads to information on the density and structure of the ejecta and the circumstellar medium, and the abundances in these media. The emphasis here is on the physical processes related to the interaction.Comment: 22 pages, 7 figures, to appear as a Chapter in "Supernovae and Gamma-Ray Bursts," edited by K. W. Weiler (Springer-Verlag

On the spherical-axial transition in supernova remnants

A new law of motion for supernova remnant (SNR) which introduces the quantity of swept matter in the thin layer approximation is introduced. This new law of motion is tested on 10 years observations of SN1993J. The introduction of an exponential gradient in the surrounding medium allows to model an aspherical expansion. A weakly asymmetric SNR, SN1006, and a strongly asymmetric SNR, SN1987a, are modeled. In the case of SN1987a the three observed rings are simulated.Comment: 19 figures and 14 pages Accepted for publication in Astrophysics & Space Science in the year 201