Geology of Northern Ireland: our natural foundation

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Cover: Geology of Northern Ireland: our natural foundation

Contents

Introduction

Basement structure and the terrane model

Introduction
Rise and fall of the Iapetus Ocean
Terrane assembly in Ireland
Central Highlands (Grampian) Terrane
Midland Valley Terrane
Southern Uplands-Down-Longford Terrane

Central Highlands (Grampian) Terrane - metamorphic basement

Introduction
Pre-Dalradian basement
Lough Derg Inlier (Lough Derg Group: Slishwood Division)
Central Inlier (Corvanaghan Formation)
Dalradian Supergroup
Stratigraphy
Argyll Group
Sperrin Mountains
Southern Highland Group
South Sperrin Mountains
North Sperrin Mountains and North Co. Londonderry
West Co. Tyrone
Northeast Co. Antrim
Deformation of the Dalradian
Regional metamorphism

Midland Valley Terrane

Introduction
Tyrone Igneous Complex
Tyrone Plutonic Group
Tyrone Volcanic Group
Early Palaeozoic arc-related intrusives
The Grampian Orogeny
The late Ordovician-early Silurian sedimentary cover sequence
Pomeroy Inlier
Desertcreat Group
Little River Group
Lisbellaw Inlier

Southern Uplands-Down-Longford Terrane

Introduction
Tectonostratigraphic models: the ‘Southern Uplands Controversy’
Stratigraphy
Crawford Group
Moffat Shale Group in Counties Down and Armagh
Leadhills Supergroup in Counties Down and Armagh
Gala Group
Hawick Group
Tectonic structure
Folding
Cleavage
Faults
Metamorphism

Late Palaeozoic intrusives

Introduction
Newry Igneous Complex
The ultramafic-intermediate complex
The granodiorite plutons
Lamprophyre intrusions

Devonian

Introduction
Stratigraphy
Fintona Group
Fintona Block
Tedd Cross Roads Segment
Irvinestown Segment
Composition and age of the palynomorph assemblages
South of the Tempo-Sixmilecross Fault
Cross Slieve Group and Red Arch Formation, Northeast Co. Antrim

Carboniferous

Introduction
Litho- and biostratigraphy
Eastern Carboniferous outliers of Ballycastle, Cultra, Castle Espie and Carlingford
Ballycastle
Cultra
Castle Espie
Carlingford
Co. Londonderry
Fintona Block
Tempo-Lisbellaw Segment
Kilskeery Group (Table 7.5)
Milltown Segment
Greenan Sandstone Formation (Table 7.1)
Slievebane Group (Table 7.6)
Co. Armagh
Tyrone Group
Armagh Group
East Co. Tyrone
Tyrone Group (Table 7.7)
Armagh Group
Leitrim Group
Millstone Grit
Coal Measures
Newtownstewart Outlier
Co. Fermanagh-south Co. Tyrone
Derrygonnelly-Marble Arch-Cuilcagh Mountain
Tyrone Group
Leitrim Group
Lisnaskea
Tyrone Group
Leitrim Group
Fivemiletown-Clogher-Aughnacloy-Benburb
Fivemiletown-Clogher
Tyrone Group
Aughnacloy
Benburb
Kesh-Omagh
Omagh Sandstone Group
Tyrone Group
Palaeogeographical and environmental reconstruction
Late Courceyan (CM Biozone)
Chadian (Pu Biozone)
Arundian
Holkerian
Early Asbian
Late Asbian
Brigantian–Arnsbergian
Late Namurian-Westphalian A/B
Late Carboniferous-Early Permian

Variscan (Hercynian) Orogenic Cycle

Variscan (Hercynian) Orogenic Cycle — detail
Late Tournaisian-early Viséan extension
Late Holkerian-early Asbian
Late Asbian
Late Asbian-Brigantian
Late Viséan-early Namurian
Late Namurian-Westphalian B (early Duckmantian)
Post-Westphalian B

Permian

Introduction
Stratigraphy
Belfast Lough
Newtownards
East Co. Tyrone
Armagh
Larne No. 2 borehole
North Co. Antrim

Triassic

Introduction
Sherwood Sandstone Group
Depositional environment
Mercia Mudstone Group
Penarth Group
Waterloo Mudstone Formation
Depositional environment and tectono-depositional model for the Triassic in Northern Ireland
Depositional environment
Tectono-depositional model for the Triassic in Northern Ireland

Jurassic

Introduction

Cretaceous

Introduction
Structural setting and depositional history
Hibernian Greensands Formation
Ulster White Limestone Formation
Pre-Larry Bane Chalk White Limestone
Larry Bane Chalk Member
Post-Larry Bane Chalk White Limestone

The Cretaceous-Palaeogene (K-T) Boundary

Introduction

Palaeogene extrusive igneous rocks

Mantle plumes, ocean spreading and the North Atlantic Igneous Province
Stratigraphy and chronology
Antrim Lava Group

Palaeogene intrusive igneous rocks

Introduction
Intrusive centres
Carlingford Complex
Mourne Mountains Complex
Slieve Gullion Complex
Minor igneous intrusions
Dykes
Plugs
Sills

Late Palaeogene (Oligocene) sedimentary basins

Introduction
Lough Neagh Group
Dunaghy Formation
Ballymoney Formation
Sediment provenance in the Lough Neagh Group

Post-Variscan deformation and basin formation

Introduction
Development of Permo-Triassic basins in Northern Ireland
Rathlin and Lough Foyle basins
Lough Neagh Basin
Larne Basin
South Co. Antrim and north Co. Down
Newtownards Trough
Post-Mesozoic structural history
Opening of the North Atlantic Ocean
Intrusions controlled by ring fractures
Doming associated with magmatism
Crustal dilation
Late to post-Palaeogene faulting
NNW-SSE trending faults
Northeast-southwest trending faults

Quaternary

Introduction
Pleistocene
Last Interglacial (Ipswichian) Stage
Midlandian Cold Stage
Early Midlandian
Fermanagh Stadial
Aghnadarragh Interstadial
Middle Midlandian
Late Midlandian
Glenavy Stadial
Killard Point Stadial
Woodgrange Interstadial
Nahanagan Stadial
Holocene
The influence of people in Northern Ireland

Geophysics and concealed geology

Introduction
Aeromagnetic data
Gravity data
Image processing
Rock properties
Density
Magnetic properties
Geophysical domains
Dyke swarms
Geophysical lineaments: faults and terrane boundaries
Terrane boundaries
Other major Caledonoid lineaments and faults
NNW-SSE to NNE-SSW trending faults and lineaments
Omagh Lineament
Draperstown Lineament
Antrim-Down Lineament
Garron Point - Conlig Lineament
Other trends
Intrusive bodies
Modelling
Highland Border Ridge (Figure 19.6)
Foyle, Rathlin and Larne sedimentary basins (Figure 19.7)
Lough Neagh Basin, Newry Igneous Complex and Mourne Mountains Central Complex (Figure 19.8)
3D model of the Antrim Plateau (Figure 19.9)

Hydrogeology

Introduction
Northern Ireland’s aquifers
Class 1
Class 2
Class 3
Aquifer potential
Groundwater chemistry
Groundwater vulnerability

Minerals

Introduction
Precious metals (gold and silver)
Mesothermal quartz vein-hosted gold
Central Highlands (Grampian) Terrane (Dalradian Supergroup)
Southern Uplands-Down-Longford Terrane (Leadhills Supergroup)
Stratabound gold occurrences
Volcanogenic gold occurrences
Alluvial gold
Base metals
Lead and zinc
Copper
Tin
Diamonds and semi-precious gems
Bulk minerals
Lateritic iron ores
Iron ores
Bauxite
Industrial minerals
Rock Salt (halite)
Gypsum and anhydrite
Perlite
Diatomite
Barytes
Glass sand
Moulding sand
Feldspar
Fireclay
Ball clay
Dolomite
Chalk
Construction minerals
Aggregate
Brickclay
Dimension Stone
Fuel minerals
Coal
Lignite
Peat
Uranium

Oil and gas

Introduction
Early Carboniferous basins in Co. Fermanagh and south Co. Tyrone
Play model
Reservoirs
Source rocks
Quality
Maturity
Seals
Burial history, hydrocarbon generation and trapping mechanisms
Permo-Triassic basins
Play model
Reservoir
Source rocks
Maturity
Seals
Burial history, hydrocarbon generation and trapping mechanisms
Trapping styles

Geohazards

Introduction
Subsidence
Compressible ground
Underground cavities
Slope stability
Landslides
Erosion, deposition and flooding

Foreward

The Geology of Northern Ireland: our natural foundation

In the years since the first edition of The Geology of Northern Ireland was published in 1972 many new theories have become generally accepted in geology, and perhaps the most significant of these is the understanding of plate tectonics. This, in conjunction with an increasing knowledge of other geological processes, has required a re-examination of the geological history of Northern Ireland.

The first edition was the earliest publication to describe the detailed geology and landscape of Northern Ireland for both geologists and non-geologists. That it is only now necessary to update it is a tribute to the author, the then Director of the Geological Survey of Northern Ireland, Harry Wilson.

The Geology of Northern Ireland-Our Natural Foundation gives a comprehensive account of the rocks and deposits shown on the 1997 edition of the 1:250 000 scale geological map of Northern Ireland and is written primarily for geologists and geoscientists. However, it is also intended to be of value to planners, civil engineers and environmental scientists who require an overview of the geology of Northern Ireland. In addition, we hope that it will attract the interest of walkers, naturalists, cavers, climbers and other outdoor-based pursuits that spend time on the bedrock and superficial deposits that are our natural foundation. In addition to providing a comprehensive account of the geology of the region, The Geology of Northern Ireland complements other GSNI publications, including ‘A Story through Time’ and the ‘Explore’ and ‘Walk’ guides from the Landscapes from Stone project. The publication also includes new and unpublished information contained in the archive of the GSNI.

Northern Ireland represents a small area of the Earth’s surface but yet contains a wide array of rock types, of many different geological ages, which are reflected in the variety of landscapes present. These extend from the high moorland of the Antrim Plateau with the magnificent Glens of Antrim along the north and eastern coastal fringes, to the rolling fields of Counties Down and Armagh, which are pierced by the Mountains of Mourne and Slieve Gullion in the south and east. In the northwest, the rounded and glaciated peaks of the Sperrin Mountains give way to the maze of waterways of the Fermanagh Lakeland in the southwest. All of these landscapes reflect the interaction between the underlying rocks and geological processes that give rise to the varied environmental niches that support our widely varied natural flora and fauna.

The Geology of Northern Ireland endeavors to present detailed geological information in a systematic and user-friendly way. Each chapter, commencing with the oldest rocks and progressing through time to the final glacial episode, allows the reader to understand the setting of each geological period on national, regional, local and individual locality scale. It is hoped that the provision of general information, supported by detailed maps,will facilitate visits to areas too long regarded as being ‘off-the-beaten-track’ and will act as a guide to localities of outstanding geological significance. Therefore, in almost every chapter, sites of national or international significance are described and augmented by photographs, largescale maps and grid references. The book also provides an up-to-date account of the results of mineral and hydrocarbon exploration and reflects on the prospects of new discoveries being made in Northern Ireland.

In compiling The Geology of Northern Ireland, the GSNI have drawn heavily on the expertise and experience of staff of the British Geological Survey and of academic staff at universities in Ireland and Britain. Their efforts are gratefully acknowledged. Detailed knowledge of the geology of an area can help reduce risk in all scales of development. The GSNI hope that The Geology of Northern Ireland-Our Natural Foundation will highlight the value of geological information. A geologist is never more than a phone call away!

David Falvey, PhD, Executive Director, British Geological Survey, Keyworth, Nottingham. NG12 5GG

Eur Geol Garth Earls Director, Geological Survey of Northern Ireland, 20 College Gardens Belfast. BT9 6BS

Acknowledgements

The following geologists provided excellent advice and encouragement whilst reviewing chapters of the new book: Dr Bernard Anderson (formerly Queen’s University Belfast (QUB), Chapters 1, 3, 8, 17). Mr John Mendum (British Geological Survey (BGS), Chapter 2), Dr Jim Floyd (BGS, Chapter 4). Dr Ian Meighan (QUB), Chapters 5, 15), Dr Mike Stephenson (BGS, Chapter 6). Dr Ian Somerville (University College Dublin, Chapter 7). Dr Geoff Warrington (formerly BGS, Chapters 9, 10, 11), Dr Jim Riding (BGS, Chapters 12, 13, 16). Dr Paul Lyle (University Ulster Jordanstown, Chapter 14). Prof Marshall McCabe (University Ulster Coleraine (UCC), Chapter 18). Mr Sam Holloway (BGS, Chapter 19), Mr Nick Robins (BGS, Chapter 20) and Dr Alastair Ruffell (QUB, Chapter 22). Dr Ian Meighan kindly provided information on geoarchaeology for Chapter 18 (Quaternary). The final review of all the chapters by Prof Tony Bazley has greatly improved the book.

In addition the GSNI has received assistance and advice from staff in the GSNI and BGS and from associates in museums, universities and institutes throughout Ireland and Britain. I hope that the following list is exhaustive. Mr Tim Cullen (BGS, Photography). Mr Brian Routledge (Ulster Museum, Belfast (UM), Photography). Mr Hugh Crilly (GSNI, Cartography), Mr Andy Hulbert (BGS, Cartography). Ms Janis Smyth (formerly BGS, Cartography), Dr Alan Brandon (formerly BGS, Chapter 7). Mr Alex Donald (GSNI, IT support), Ms Dee Flight (BGS, Chapter 21). Dr Jasper Knight (Edge Hill College, Chapter 18). Dr Steve McCarron (Trinity College Dublin, Chapter 18). Dr Patrick McKeever (GSNI, Photographs), Dr John Morris (Geological Survey of Ireland-GSI). Mr Derek Reay (GSNI), Dr Ian Somerville (Photographs), Mr Geoff Warke (BGS, Photographs). Mr Mark Williams (BGS, Chapter 3), Dr Neil Clark (Hunterian Museum, Glasgow). Dr Mike Howe (BGS), Mr Ken James (UM), Dr Matthew Parkes (GSI), Dr Mike Simms (UM). Mrs Pauline Taylor (BGS), Dr Mark Woods (BGS).

Permission to use company data in (Figure 16.2, Boreholes 2 and 3) was received from Ballymoney Power. Front cover Landsat TM5 image and Chapter 15, Photograph 1 © Natural Environment Research Council; Back cover Photographs of Dunluce Castle and Strangford Lough, Chapter 12, Photograph 1