This report describes the model of faulted bedrock of the Lower Cretaceous to Lower Devonian sedimentary sequence found within the Great Glen corridor, including the upper reaches of the Moray Firth, (Figure 1)

Arkley, S.L.B.

NERC Open Research Archive

     Model metadata report for the Great Glen – Moray Firth GSI3D Faulted Bedrock Model   Geology and Regional Geophysics Scotland OR/14/058         BRITISH GEOLOGICAL SURVEY Geology and Regional Geophysics Scotland OR/14/058   The National Grid and other Ordnance Survey data © Crown Copyright and database rights 2014. Ordnance Survey Licence No. 100021290.  Keywords GSI3D, Bedrock Model, Great Glen, Moray Firth. Front cover Image from GSI3D window showing geological units and faults. Bibliographical reference ARKLEY, S.L.B 2014. Model metadata report for the Great Glen – Moray Firth GSI3D Faulted  Bedrock Model.  British Geological Survey Internal Report, OR/14/058.  14pp. Copyright in materials derived from the British Geological Survey’s work is owned by the Natural Environment Research Council (NERC) and/or the authority that commissioned the work. You may not copy or adapt this publication without first obtaining permission. Contact the BGS Intellectual Property Rights Section, British Geological Survey, Keyworth, e-mail ipr@bgs.ac.uk. You may quote extracts of a reasonable length without prior permission, provided a full acknowledgement is given of the source of the extract. Maps and diagrams in this book use topography based on Ordnance Survey mapping.  Model metadata report for the Great Glen – Moray Firth GSI3D Faulted Bedrock Model Arkley, S.L.B. Editor Callaghan, E.A.   © NERC 2014. All rights reserved Keyworth, Nottingham   British Geological Survey   2014 The full range of our publications is available from BGS shops at Nottingham, Edinburgh, London and Cardiff (Welsh publications only) see contact details below or shop online at www.geologyshop.com The London Information Office also maintains a reference collection of BGS publications, including maps, for consultation. We publish an annual catalogue of our maps and other publications; this catalogue is available online or from any of the BGS shops. The British Geological Survey carries out the geological survey of Great Britain and Northern Ireland (the latter as an agency service for the government of Northern Ireland), and of the surrounding continental shelf, as well as basic research projects. It also undertakes programmes of technical aid in geology in developing countries. The British Geological Survey is a component body of the Natural Environment Research Council. British Geological Survey offices  BGS Central Enquiries Desk Tel 0115 936 3143 Fax 0115 936 3276 email enquiries@bgs.ac.uk  Kingsley Dunham Centre, Keyworth, Nottingham  NG12 5GG Tel 0115 936 3241 Fax 0115 936 3488 email sales@bgs.ac.uk  Murchison House, West Mains Road, Edinburgh  EH9 3LA Tel 0131 667 1000 Fax 0131 668 2683 email scotsales@bgs.ac.uk Natural History Museum, Cromwell Road, London  SW7 5BD Tel 020 7589 4090 Fax 020 7584 8270 Tel 020 7942 5344/45 email bgslondon@bgs.ac.uk Columbus House, Greenmeadow Springs, Tongwynlais, Cardiff  CF15 7NE Tel 029 2052 1962 Fax 029 2052 1963 Maclean Building, Crowmarsh Gifford, Wallingford   OX10 8BB Tel 01491 838800 Fax 01491 692345 Geological Survey of Northern Ireland, Colby House, Stranmillis Court, Belfast  BT9 5BF Tel 028 9038 8462 Fax 028 9038 8461 www.bgs.ac.uk/gsni/ Parent Body Natural Environment Research Council, Polaris House, North Star Avenue, Swindon  SN2 1EU Tel 01793 411500 Fax 01793 411501 www.nerc.ac.uk  Website  www.bgs.ac.uk  Shop online at  www.geologyshop.com      BRITISH GEOLOGICAL SURVEY  CONTENTS Summary ......................................................................................................................................... 3 1 Modelled volume, purpose and scale ....................................................................................... 3 2 Modelled surfaces/volumes ...................................................................................................... 4 3 Modelled faults ......................................................................................................................... 5 4 Model datasets .......................................................................................................................... 6 4.1 Borehole Data ................................................................................................................. 6 4.2 Map Data ........................................................................................................................ 6 4.3 DTM Data ....................................................................................................................... 6 4.4 existing section data........................................................................................................ 7 4.5 GVS and GLEG .............................................................................................................. 8 5 Dataset integration ................................................................................................................... 8 6 Model development log ............................................................................................................ 8 7 Model workflow ....................................................................................................................... 9 8 Model assumptions, geological rules used etc ....................................................................... 10 9 Model limitations ................................................................................................................... 10 References ..................................................................................................................................... 11  FIGURES Figure 1: Location of modelled area, outlined in red ...................................................................... 3 Figure 2: Onshore geology based on the BGS 1:625 000 onshore geological map ........................ 4 Figure 3: Offshore geology based on the BGS 1:250 000 offshore geological map ...................... 5 Figure 4: Faults modelled as shown in the GSI3D map window and 3D window from the GB-3D project. ...................................................................................................................................... 5 Figure 5: Additional steep dipping faults as shown in the GSI3D 3D window. ............................. 6 Figure 6: Cross-sections as seen in GSI3D window, left for original model. Close up view of cross sections, right. Note that many of the longer sections only contain data within the model area for Devonian and younger rocks: older strata from GB-3D lines have been removed as they have been superseded by more recent versions. ............................................ 7 Figure 7: Cross-section GG_section_3 from GSI3D cross-section window showing Devonian and younger rocks, vertical exaggeration x5 ............................................................................ 8 Figure 8: Surfaces of each geological unit displayed in the 3D window, as calculated in 2011. ... 9 Figure 9: Extent of geological unit with 'holes' as calculated in 2011 .......................................... 10  TABLES Table 1: Geological units modelled ................................................................................................ 4   2  Summary This report describes the model of faulted bedrock of the Lower Cretaceous to Lower Devonian sedimentary sequence found within the Great Glen corridor, including the upper reaches of the Moray Firth, (Figure 1).   1 Modelled volume, purpose and scale The model was based initially on sections drawn for the GB_3D to test and develop GSI3D’s bedrock capabilities in complex geological terranes and to improve our geological understanding of the geology/structure of the area for the Lower Devonian – Cretaceous sedimentary succession. The model is suitable for use at scales between 1:250 000 – 1:750 000 and to a depth of 3,000 m.   Figure 1: Location of modelled area, outlined in red     3  2 Modelled surfaces/volumes The sedimentary sequence consists of 9 geological units:  Units modelled   Offshore equivalents  LOCR-SSML Lower Cretaceous CRKN-ARG Cromer Knoll Group JURU-SDSM Upper Jurassic HMBG-ARSL Humber Group JURM-MDSL Middle Jurassic FLDN-SMC & JURM-ARSM Fladen Group – Middle Jurassic Rocks LI-MSLS Lias,Lower Jurassic LI-SDAR Lias Group NRS-SDBC Permian-Triassic PRMT-SDAR Permian and Triassic Rocks (undifferentiated) UDEV-SCON Upper Devonian UORS-SDST Upper Old Red Sandstone MDEV-SCON Middle Devonian MDEV-COSD Middle Devonian  (undifferentiated) LORS-CSSM Lower Devonian   ORS-CSSM undifferentiated Devonian,slices within fault zones    Table 1: Geological units modelled  The onshore geology is based on the BGS 625 000 geological map. The offshore geology is based on the BGS 250 000 map. All units are labelled with BGS LEX-RCS codes, see Figures 2 and 3. Geological units modelled are as used in the GB_3D sections on which the model is based. Offshore units were merged into their onshore equivalents, as shown in Table 1.      Figure 2: Onshore geology based on the BGS 1:625 000 onshore geological map  4   Figure 3: Offshore geology based on the BGS 1:250 000 offshore geological map  3 Modelled faults Seven faults were initially included in the model from the GB_3D project, (Figure 4). Fault selection included the largest faults known in the area. Where fault zones exist they have been simplified to a single fault. All faults have been modelled as planar structures with a steep dip. Two of the faults which extended way beyond the project area were clipped so their extent is within the model DTM. Some of the fault lines were edited to better fit with the geological map. Crossing faults were checked for complete overlap at depth, and that a single node extended beyond the crossing fault. Fault helper sections were drawn at the end of faults which pinched out within the project area. During the course of the work an additional 31 steeply dipping faults were modelled, (Figure 5).   Figure 4: Faults modelled as shown in the GSI3D map window and 3D window from the GB-3D project.   5   Figure 5: Additional steep dipping faults as shown in the GSI3D 3D window. 4 Model datasets  4.1 BOREHOLE DATA No borehole data has been used in the construction of the model. Although there are a number within the area, the majority are either too shallow or not detailed enough to help with this model.   4.2 MAP DATA • Topographic map, 1:1 000 000 scale, clipped from the GDI, with attached world file. • Onshore geological information, 625 000 bedrock, superficial and faults, clipped from the GDI. • Offshore geological information, 250 000 bedrock and faults were clipped from the GDI. The data was re-projected to British National Grid to be compatible with the onshore datasets. The offshore map data does not colour up in GSI3D as it has different LEX-RCS units to those in the GVS/GLEG.    4.3 DTM DATA The ‘Bald Earth’ DTM was extracted at 250 m resolution and is stored as a TIN within the GSI3D workspace. A model limitation is that bedrock units are drawn up to Bald Earth DTM rather than to the base of the superficial deposits (rockhead surface).    6  4.4 EXISTING SECTION DATA Currently 37 existing sections have been used: (Figure 6): • The model is based on geological information shown in 9 sections imported from the GB_3D project. These sections were drawn by ‘regional geologists’ and have been largely unchanged, only minor edits were made in places to provide consistency, in addition to snapping to crossing sections and outcrops/subcrops. • A section on the Moray-Buchan 250 000 map across the Moray Firth was scanned, saved as a raster and imported as a backdrop image to a section to help give some control on the thicknesses of units in that area. Sections on the onshore 50 000 maps are shallow and deemed not worth importing. • An additional network of 13 sections was used to constrain the model.  • 4 Sections bound the model edges. • 6 Fault helper sections were drawn where faults pinch out within the project. • 4 Additional helper sections were needed to ensure there is a section passing through each polygon shown on the geological map such as several small Permian and Devonian outliers in the south-east of the model.    Figure 6: Cross-sections as seen in GSI3D window, left for original model. Close up view of cross sections, right. Note that many of the longer sections only contain data within the model area for Devonian and younger rocks: older strata from GB-3D lines have been removed as they have been superseded by more recent versions.   7   Figure 7: Cross-section GG_section_3 from GSI3D cross-section window showing Devonian and younger rocks, vertical exaggeration x5   4.5 GVS AND GLEG The GVS and GLEG are used in the GB3D project, see Appendix 1.   5 Dataset integration Each piece of information was added individually as and when required, then removed to retain a small file size and fast calculation time. 6 Model development log Modelling was completed by Sarah Arkley in September/October 2011. The model was subsequently checked for snapping and consistency in 2014. Additionally, the pre-Devonian interpretations were removed since they have been superseded by the newer ‘crustal model’, the GB-3D interpretations may have been superseded since modelling, and these older units did not have constraining baselines.   Final version of the model is located at:  W:\Teams\QES\QMMP\Data\MorayNessBasin_Data\GSI3D Great Glen to Moray Firth\GREAT GLEN-MORAY FIRTH Regional Model\Great_Glen_bedrock_approved\Final_model_files  8  7 Model workflow • The project workspace was created by copying the latest version of the GB_3D project, dated 15th Sept 2011, (GB_3D_Completed_Sections_v30_GL_v7.gsipr). The faults and sections which lay out with the Great Glen – Moray Firth project area were stripped out. The GVS and GLEG were retained and a new DTM was created. • Small edits were made to the faults before calculating the ‘fault network’. • Existing GB_3D sections were correlated and new sections were drawn. • Baselines were drawn for each geological unit based on the relevant geological map. • Geological units were calculated. • Numerous edits to sections were completed in an attempt to obtain fully calculated surfaces.  The fault network calculates correctly. However whilst the bedrock surfaces can be calculated to produce a surface (Figure 6), most surfaces have holes (uncalculated portions), Figure 7. The GSI3D software was under development for bedrock at the time of modelling. Subsequently the development was stopped and so the issue of holes within the calculated surfaces was not resolved. The model is therefore submitted to the National Geological Model as a ‘cross-section only’ project       Figure 8: Surfaces of each geological unit displayed in the 3D window, as calculated in 2011.    9   Figure 9: Extent of geological unit with 'holes' as calculated in 2011 8 Model assumptions, geological rules used etc • All faults have been drawn planar with a steep dip • There was little control on the thickness of units, thus a constant unit thickness was assumed in most places onshore with some thickening towards the basin centre in the Moray Firth 9 Model limitations • No ‘superficial geology’, ‘water’ are currently modelled, thus the bedrock units are modelled to the DTM rather than to rockhead.  • Only selected faults are included in the model and some of these are simplified. More faults could be added and existing faults could be better shaped to provide a fault network which is more geologically realistic and better portrays our current understanding of the structure of the area. • Blank section lines extend far beyond the project area because they were imported from GB-3D, truncating the sections did not prove successful.  • The project is to be treated as ‘cross-section only’ due to problems with calculation as discussed above.         10  References British Geological Survey holds most of the references listed below, and copies may be obtained via the library service subject to copyright legislation (contact libuser@bgs.ac.uk for details). The library catalogue is available at: http://geolib.bgs.ac.uk.  Kessler, H., Mathers, S.J., Sobisch, H-G and Neber, A..2008. GSI3D – The software and methodology to build systematic near-surface 3-D geological models. (Version 2) British Geological Survey Open Report, OR/08/001 144pp.   11 

Model metadata report for the Great Glen : Moray Firth GSI3D Faulted Bedrock Model

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Model metadata report for the Great Glen : Moray Firth GSI3D Faulted Bedrock Model

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