Lithostratigraphy and biostratigraphy of the Lower Carboniferous (Mississippian) carbonates of the southern Askrigg Block, North Yorkshire, UK

A rationalized lithostratigraphy for the Great Scar Limestone Group of the southeast Askrigg Block is established. The basal Chapel House Limestone Formation, assessed from boreholes, comprises shallow-marine to supratidal carbonates that thin rapidly northwards across the Craven Fault System, onlapping a palaeotopographical high of Lower Palaeozoic strata. The formation is of late Arundian age in the Silverdale Borehole, its northernmost development. The overlying Kilnsey Formation represents a southward-thickening and upward-shoaling carbonate development on a south-facing carbonate ramp. Foraminiferal/algal assemblages suggest a late Holkerian and early Asbian age, respectively, for the uppermost parts of the lower Scaleber Force Limestone and upper Scaleber Quarry Limestone members, significantly younger than previously interpreted. The succeeding Malham Formation comprises the lower Cove Limestone and upper Gordale Limestone members. Foraminiferal/ algal assemblages indicate a late Asbian age for the formation, contrasting with the Holkerian age previously attributed to the Cove Limestone. The members reflect a change from a partially shallow-water lagoon (Cove Limestone) to more open-marine shelf (Gordale Limestone), coincident with the onset of marked sea-level fluctuations and formation of palaeokarstic surfaces with palaeosoils in the latter. Facies variations along the southern flank of the Askrigg Block, including an absence of fenestral lime-mudstone in the upper part of the Cove Limestone and presence of dark grey cherty grainstone/packstone in the upper part the Gordale Limestone are related to enhanced subsidence during late Asbian movement on the Craven Fault System. This accounts for the marked thickening of both members towards the Greenhow Inlier

Mississippian reef development in the Cracoe Limestone Formation of the southern Askrigg Block, North Yorkshire, UK

The southern margin of the Askrigg Block around Cracoe, North Yorkshire, shows a transition from carbonate ramp to reef-rimmed shelf margin, which, based on new foraminiferal/algal data, is now constrained to have initiated during the late Asbian. A late Holkerian to early Asbian ramp facies that included small mudmounds developed in comparatively deeper waters, in a transition zone between the proximal ramp, mudmound-free carbonates of the Scaleber Quarry Limestone Member (Kilnsey Formation) and the distal Hodderense Limestone and lower Pendleside Limestone formations of the adjacent Craven Basin. The ramp is envisaged as structurally fragmented, associated with sudden thickness and facies changes. The late Asbian to early Brigantian apron reefs and isolated reef knolls of the Cracoe Limestone Formation include massive reef core and marginal reef flank facies, the latter also including development of small mudmounds on the deeper water toes of back-reef flanks. The position of the apron/knoll reefs is constrained to the south (hangingwall) of the North Craven Fault, but it is syn-depositional displacement on the Middle Craven Fault that accounts for the thick reefal development. Subsequent inversion of this structure during the early Brigantian caused uplift and abandonment of the reefs and consequent burial by the Bowland Shale Formation

Hydraulic fracturing: a review of theory and field experience

This report summarises the current state-of-the-art knowledge of the hydraulic fracturing process used by the shale gas/oil industry using open peer-reviewed literature and from government commissioned research reports. This report has been written to make statements on our knowledge of the following questions: • How do hydrofractures form? • How far do hydrofractures extend during stimulation? • What dictates where hydrofractures propagate? • How do hydrofractures interact with the existing fracture network? • Can the size and distribution of hydrofractures be controlled? Gaps in our knowledge have been highlighted, with the largest of these resulting from differences between North American and European shale rocks

Geophysical surveys to help map buried igneous intrusions, Snowdonia, North Wales, UK

The geology of the Snowdonia National Park in North Wales comprises a mixture of Lower Palaeozoic shallow marine sediments, acidic igneous rocks and basic intrusions of the Welsh Basin that were subsequently deformed during the Caledonian Orogeny. Thin igneous intrusions are challenging to map due to variable surface exposures, their intrusive origin, structural deformation and burial by glacial sediments. This study used a combination of traditional geological techniques, near-surface geophysical surveys and remote sensing to detect and map a buried dolerite sheet intrusion. Both simple and mathematical analysis of magnetic anomalies and numerical modelling allowed the dolerite position, depths and target widths to be determined. Results showed that calibrated magnetic surveys can characterize buried igneous bodies in such mountainous environments

Onshore carboniferous basins : third review report

focussed on achieving a better understanding of the Bowland Shale in northern England. The broad aim is to understand the geological variability of the formation from a basin- through to microscale, and assess the impact of variability on hydrocarbon generation, storage and production (for example, the co-incidence or otherwise of factors including organic content and kerogen type; mineralogy; and engineering behaviour). This report is the third summary report describing activities of the consortium, covering the period October 2015 – June 2016. A series of 3 inter-related work packages are designed to improve understanding of the Bowland Shale of northern England. The original numbering of these is retained to allow continuity between previous progress reports. Specifically, these work packages address: 1. Work Package 1,2: Basin analysis of the Pennine Basin; Characterization of shale facies; 2. Work Package 3: Development of chemical stratigraphies through prospective parts of the stratigraphic column; 3. Work Package 4: Hydromechanical behaviour of shales. Two work packages outside the consortium are also considered, namely 4. Retrieval of new materials to test 5. Reprocessing of 3D seismic data to assess rock properties Descriptions of previous activities have been released, covering the period July 2014 to March 2015 (Hough et al., 2015a), and the period April 2015 to September 2015 (Hough et al., 2015b). The consortium currently has 4 sponsors who each contribute £25 000 per year; BGS contributes around £200 000 annually, which results in an annual budget of approximately £300 000. The consortium is planned to last 3 years initially, and started in July 2014 with a scheduled end date of June 2017

3DKL v1.0: creating the first 3D geological model of Kuala Lumpur

The objective of UN Sustainable Development Goal 11 is to make cities and human settlements inclusive, safe, resilient and sustainable. Geoscience can play a significant role in achieving targets within this goal by developing a better understanding of geological properties and processes within urban environments, and by ensuring that this understanding is integrated into urban development. A key step in this process will be enhancing awareness of urban geology among non-geoscience decision-makers, so that inherent subsurface risks and benefits are understood and accounted for during all phases of development. Three-dimensional geological models are an effective tool for geologists to communicate with stakeholders in government and industry during that process. They can also provide a framework to enable geological data and information to be integrated into Building and City Information Models, and thus facilitate more effective infrastructure and utility asset management. This paper describes the modelling workflow adopted by a consortium of geoscientists from government, industry and academia to deliver the first 3D geological model of Kuala Lumpur – 3DKL v1.0. The modelling workflow involved: digitising borehole logs from site investigation reports and storing them in a dedicated geospatially-enabled SQLite borehole database; viewing and interpreting that borehole data using QGIS software; generating multiple orthogonally oriented cross-section profiles across the modelled area using Groundhog Desktop software; and integrating the information derived from the interpreted boreholes, surface data and cross-section profiles to generate a 3D geological model in Leapfrog Geo software. 3DKL v1.0 has demonstrated proof-of-concept: we have developed a workflow, based largely on freely-available software, for transforming borehole information, previously captured in paper records, into a conceptual 3D model. The modelling process has also identified areas where geological knowledge and data need to be enhanced if 3DKL is to fulfil its potential to support more sustainable and resilient urban development in Kuala Lumpur

First attempt at measuring the CMB cross-polarization

We compute upper limits on CMB cross-polarization by cross-correlating the PIQUE and Saskatoon experiments. We also discuss theoretical and practical issues relevant to measuring cross-polarization and illustrate them with simulations of the upcoming BOOMERanG 2002 experiment. We present a method that separates all six polarization power spectra (TT, EE, BB, TE, TB, EB) without any other "leakage" than the familiar EE-BB mixing caused by incomplete sky coverage. Since E and B get mixed, one might expect leakage between TE and TB, between EE and EB and between BB and EB - our method eliminates this by preserving the parity symmetry under which TB and EB are odd and the other four power spectra are even.Comment: Polarization movies can be found at http://www.hep.upenn.edu/~angelica/polarization.htm

Diffuse source separation in CMB observations

We review issues and methods for diffuse component separation in the context of Cosmic Microwave Background observation

A guide to a new Geographical Information System for the Chalk of the Thames Basin : the Thames Chalk Information System (TCIS)

BGS work on the Chalk Group of the Thames Basin has amassed large quantities of geological information about thickness, facies, marker-beds, biostratigraphy and structure, only a small part of which is incorporated into the geological map. More recently there has been wider use and interpretation of borehole data to underpin the development of 3D geological models. There is a pressing need to organise these disparate data in a way that can easily be compared and interrogated, as well as to capture the results of relevant published research outside BGS. This project addresses this need by creating a new spatial database, the Thames Chalk Information System (TCIS). The database uses ArcGIS technology to display key information layers about the Chalk. As well as standard topographical and geological information, TCIS includes layers describing: Group, Subgroup, and formational thickness; structural data; detailed stratigraphical data; coverage of 3D geological models that include units or surfaces of the Chalk Group; regions where data coverage limits our understanding of the Chalk. Hydrogeological data is currently being compiled as part of a related project; it is not currently available for incorporation into the TCIS, but will eventually be added. Basic information about the content and methodology used to compile the data in the TCIS is outlined in the main body of this report. Hydrogeological data was delivered through a separate project, and its features are the subject of a separate report. The aim of this report is to provide sufficient background information to allow meaningful use of the TCIS database; there is no new data interpretation