The Stratigraphic Nomenclature of the Irish Offshore Basins Published by the Department of the Environment, Climate and Communications gov.ie Front cover: Sheet-like basin floor sandstone beds in the Pennsylvanian Ross Sandstone Formation, Loop Head, Co. Clare. The dark, heterogeneous unit in the centre of the picture is a laterally-extensive slump deposit. (Photo: Pat Shannon) Published in Ireland by the Department of the Environment, Climate and Communications 29-31 Adelaide Road Dublin, D02 X285 ____________________________________________________________________ The Stratigraphic Nomenclature of the Irish Offshore Basins Patrick M. Shannon1, Kara L. English2,3 & Michael Hanrahan2, 4 1UCD School of Earth Sciences, University College Dublin, Belfield, Dublin, D04 V1W8, Ireland. 2Petroleum Affairs Division, Department of Communications, Climate Action and Environment, 29-31 Adelaide Road, Dublin, D02 X285, Ireland. 3Present address: Stellar Geoscience, Dublin, and UCD School of Earth Sciences, University College Dublin, Belfield, Dublin, D04 V1W8, Ireland. 4Present address: Geoscience Regulation Office, Department of the Environment, Climate and Communications, 29-31 Adelaide Road, Dublin D02 X285, Ireland. ________________________________________________________________________ Bibliographic reference The Stratigraphic Nomenclature of the Irish Offshore Basins Department of the Environment, Climate and Communications, PAD Special Publication 2/21. Table of Contents 1. INTRODUCTION .............................................................................................................. 1 2. THE NEW NOMENCLATURE FRAMEWORK .................................................................. 5 STRATIGRAPHIC NOMENCLATURE DESCRIPTION ...................................................... 7 3. PLEISTOCENE – PLIOCENE ........................................................................................... 9 EILEAN SIAR GLACIGENIC GROUP ............................................................................. 10 BRYTHON GLACIGENIC GROUP .................................................................................. 10 HEBRIDES MARGIN GROUP ......................................................................................... 11 DEMETAE GROUP ......................................................................................................... 11 4. PLIOCENE – MIOCENE ................................................................................................. 12 TROANA GROUP ........................................................................................................... 12 5. PALEOGENE (Oligocene, Eocene and Paleocene) ..................................................... 15 TOIRSGIAN GROUP ....................................................................................................... 15 Information Box No. 1: Spanish Armada ...................................................................... 17 LUNULA GROUP ............................................................................................................ 19 STRONSAY GROUP ....................................................................................................... 19 TRALEE GROUP ............................................................................................................ 20 ROCKALL-HEBRIDES VOLCANIC GROUP ................................................................... 22 6. UPPER CRETACEOUS .................................................................................................. 24 SHETLAND GROUP ....................................................................................................... 25 CHALK GROUP .............................................................................................................. 26 7. LOWER CRETACEOUS ................................................................................................. 30 CROMER KNOLL GROUP .............................................................................................. 31 Information Box No. 2: The Salmon of Knowledge ....................................................... 33 SELBORNE GROUP ....................................................................................................... 35 WEALDEN GROUP ......................................................................................................... 36 PURBECK GROUP ......................................................................................................... 38 8. UPPER JURASSIC ......................................................................................................... 40 MUCKROSS GROUP ...................................................................................................... 40 Information Box No. 3: Signal Towers .......................................................................... 42 BEARA GROUP .............................................................................................................. 42 HOOK GROUP ................................................................................................................ 45 9. MIDDLE JURASSIC ....................................................................................................... 48 KITE GROUP .................................................................................................................. 49 EAGLE GROUP .............................................................................................................. 50 i 10. LOWER JURASSIC ...................................................................................................... 52 LIAS GROUP .................................................................................................................. 53 11. TRIASSIC ..................................................................................................................... 62 PENARTH GROUP ......................................................................................................... 62 MERCIA MUDSTONE GROUP ....................................................................................... 63 SHERWOOD SANDSTONE GROUP .............................................................................. 67 12. PERMIAN ..................................................................................................................... 70 ZECHSTEIN GROUP ...................................................................................................... 70 CUMBRIAN COAST GROUP .......................................................................................... 70 APPLEBY GROUP .......................................................................................................... 71 13. CARBONIFEROUS ...................................................................................................... 72 SORREL GROUP ........................................................................................................... 72 BLACKTHORN GROUP .................................................................................................. 74 WARWICKSHIRE GROUP .............................................................................................. 74 PENNINE COAL MEASURES GROUP ........................................................................... 75 MUIRĺN GROUP .............................................................................................................. 75 SLIOGÁN GROUP .......................................................................................................... 77 BAIRNEACH GROUP ..................................................................................................... 77 CORK GROUP ................................................................................................................ 77 14. DEVONIAN ................................................................................................................... 79 15. PRE-DEVONIAN........................................................................................................... 80 16. GUIDELINES FOR NEW NAMES ................................................................................. 81 17. ACKNOWLEDGEMENTS ............................................................................................. 82 18. REFERENCES ............................................................................................................. 83 Appendix A. Application Form for Proposed New Units for the Standard Stratigraphic Nomenclature of Offshore Ireland ....................................................................................... 90 Figure 1. Map of Irish offshore sedimentary basins ............................................................... 2 Figure 2. Irish offshore stratigraphic nomenclature themes. .................................................. 7 Figure 3. Thematic relationship between new formation and member names in the Lias Group (Lower Jurassic) of offshore Ireland. ........................................................................ 53 Enclosure 1. Regional chronostratigraphic summary chart of the groups, formations and members in the Irish offshore (from Merlin Energy Resources Consortium, 2020). ii FOREWORD I am delighted to introduce this PAD Special Publication, entitled “The Stratigraphic Nomenclature of the Irish Offshore Basins”, that is a companion document to the published Standard Stratigraphic Nomenclature of Offshore Ireland: An Integrated Lithostratigraphic, Biostratigraphic and Sequence Stratigraphic