Geological framework model and surface data for the area south of Ammanford

Background The original objective of this work was to a ssemble a 1:50 000 (50k) resolution 3D Geological Framework Model for an area south of Ammanfor d. The model was to have two main purposes: 1. To form the basis for a communication tool to present the 3D geological understanding of the area to a range of stakeholders; and 2. To support the reinterpretation of th e geological succession mapped at surface. This study specifically excludes the further development of th e Framework Model to include hydrogeology, hydrochemistry or rock mechanics and does not include any consideration of potentially suitable resources such as Coal Bed Methane. This report provides the explanation of the me thodology and how this model was generated. Additional outputs of the study include: 1. An ArcGIS project containing the da ta used to compile the model; and 2. Surface observations of the geology collected foll owing Sigma workflows, held in a GIS. Development of a 3D geological framework model A 1:50 000 resolution 3D geological framework model was successfully constructed for the study area using the Geological Surveying and Investigation in 3D (GSI3D) software package, developed partly in house at BGS, which can be used readily by geologists to construct a series of cross-sections that can more clearly display the geological succession. Models of this type have the potential to be accessible to members of the public and used by geologists to assess the potential location of resources , not evident from traditi onal 2D geological maps. The approach followed was to construct a fence diagram of 12 cross-sections using GSI3D. These sections encompass the entire study area and using the geologists’ expert knowledge to incorporate surface and subsurface data (24 deep boreholes and structural contour information from published geological maps) provide an inte rpretation of the geolog ical succession at Bed, Member and Formation level, consistent with BGS 1:50 000-scale (50k) geological maps of the area

Modelling complex geological circular data with the projected normal distribution and mixtures of von Mises distributions

Circular data are commonly encountered in the earth sciences and statistical descriptions and inferences about such data are necessary in structural geology. In this paper we compare two statistical distributions appropriate for complex circular data sets: the mixture of von Mises and the projected normal distribution. We show how the number of components in a mixture of von Mises distribution may be chosen, and how one may choose between the projected normal distribution and the mixture of von Mises for a particular data set. We illustrate these methods with a few structural geological data, showing how the fitted models can complement geological interpretation and permit statistical inference. One of our data sets suggests a special case of the projected normal distribution which we discuss briefly

The Millstone Grit Group (Pennsylvanian) of the Northumberland-Solway Basin and Alston Block of northern England

In the Northumberland–Solway Basin and Alston Block of northern England, some aspects of the stratigraphical and sedimentological relationships between the Millstone Grit Group, the Stainmore Formation (Namurian part of the Yoredale Group) and the Westphalian Pennine Coal Measures Group are uncertain. Also, confusion has resulted from discontinuation of Millstone Grit as a formal lithostratigraphical term north of the Stainmore Basin. This paper presents the evidence for, and describes the nature of, a Kinderscoutian (early Pennsylvanian) abrupt transition from typical ‘Yoredale cyclicity’, characterized by marine limestones in a dominantly siliciclastic succession but including marked fluvial channels, to a sandstone-dominated fluvial succession recognizable as the Millstone Grit Group. Sandbodies present in this region are probably the fluvial feeder systems to many of the fluvio-deltaic successions recorded farther south in the Central Pennine Basin. However, onset of the Millstone Grit Group occurs much earlier to the south, during the Pendleian (late Mississippian), despite the entry of fluvial systems into the Central Pennines Basin from the north. In addition to explaining this counter-intuitive relationship, the paper also recognizes continuation of the fluvial regime into the lowermost part of the Pennine Coal Measures Group

The construction of a bedrock geology model for the UK: UK3D_v2015

This report is available for download on the BGS UK3D web page to allow the reader to better understand the context and development of UK3D, a national network, or ‘fence diagram model’, of bedrock geology cross-sections. It also explains the development of the metadata underpinning the model and therefore supports use and understanding of UK3D. The pre-existing BGS GB3D model provided the only nationally consistent representation of the bedrock geology of Great Britain to depths of at least 1 km. The latest version of this model was released in 2014 as the GB3D_v2014 and accompanying report (Mathers et al. 2014b). However, the existing GB3D_v2014 model lacked equivalent scale presentation of a fence diagram model for Northern Ireland. It was recognised that in order to provide comparable geological information across the United Kingdom it was necessary to upgrade the model to a UK3D fence diagram model incorporating Northern Ireland, with rigorous peer review performed to enable an enhanced dataset. The objective of this study was therefore to further develop the GB3D model, outlined by Mathers et al. (2014a and b), into a UK3D model by the incorporation of 36 deep boreholes and a framework of 15 cross-sections for Northern Ireland. The appropriate applications for the revised model are for geoscience communication and education to illustrate the national and regional bedrock geology of the United Kingdom to a depth of at least 1 km with an intended resolution of use in the 1:250 000 to 1:1 million scale range. Limitations inherent in the model preclude such applications as detailed geological assessments, resource-reserve estimation and exploration, and any representation or use outside the intended resolution range. The new model produced by this study UK3D_v2015 supersedes the earlier 2014 version for England and Wales, for which areas of the fence diagrams remain the same. The Scottish portion of the model remains unchanged from the earlier 2012 version. The new dataset is a wholly owned BGS product and as with its forerunners it is freely available from the BGS website http://bgs.ac.uk as downloads in a variety of formats

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