Pollen and Spore Assemblages from the Oligocene Lough Neagh Group and Dunaghy Formation, Northern Ireland

Pollen and Spore Assemblages from the Oligocene Lough Neagh Group and Dunaghy Formation, Northern Ireland John Andrew Fitzgerald B.Sc. (hoos), M.Sc. A thesis presented in partial fulfilment of the regulations for the Degree of Doctor of Philosophy VOC- r· Centre for Palynology University of Sheffield September 1999 CONTENTS VOLUME 1 SUMMARY ACKNOWLEDGEMENTS Page 1. INTRODUCTION 1 2. GEOLOGY OF THE LOUGH NEAGH GROUP 3 2.1 The Lough Neagh Group, a historical review 5 2.2 Lithology of the Lough Neagh Group 10 2.3 Mineralogy and Provenance of the Lough Neagh Group 12 2.4 Structural Setting 14 2.5 Clay Mineralogy 14 2.6 Lignite Geochemistry 15 2.7 The Coagh deposit 15 2.8 The Ballymoney Deposit 16 3. SAMPLE PREPARATION 18 3.1 Non-lignitic samples 24 3.2 Alcohol separation of organic debris 27 3.3 Density separation of pollen 31 3.4 Lignitic samples 32 3.5 The action ofKOH upon a pollen assemblage 34 3.6 Microwave assisted hydrofluoric acid maceration 36 3.7 Slide preparation and pollen abundance calculation 39 3.8 Counting technique and data recording and presentation 41 4. RELATIONSHIP OF POLLEN ABUNDANCE TO PARENT FLORAL 43 4.1 Differing pollen productivity and representation 44 4.2 Absolute and differing relative pollen productivity 49 5. LITHOLOGICAL DESCRIPTION OF SAMPLES 51 5.113/611 LandagiveyNo. 1 51 5.2 13/603 Ballymoney No.1 56 5.3 36/4680 Deerpark No.2 58 5.4 27/415 Upper Mullan No.1 61 6. SYSTEMATICS, CLASSIFICATION AND NOMENCLATURE 65 6.1 Problems of Tertiary pollen classification 66 6:2 Systems of classification 68 6.3 A solution to the taxonomical and nomenclatorial problem? 77 7. POLLEN AND SPORE SYSTEMATICS 80 7.1 Monocolpate pollen 81 7.2 Dicolpate pollen 95 7.3 Tricolpate pollen 98 7.3.1 Reticulate Tricolpate pollen 108 7.4 Tricolporate pollen 123 7.4.1 Reticulate Tricolporate pollen 142 7.5 Tetracolporate pollen 169 7.6 Syncolporate pollen 170 7.7 Monoporate pollen 174 7.8 Triporate pollen 178 7.9 Polyporate pollen 189 7.10 Inaperturate pollen 194 7.11 Monosaccate pollen 205 7.12 Bisaccate pollen 206 7.13 Alete spores 210 7.14 Monolete spores 215 7.15 Trilete spores 225 7.16 Incertae sedis 267 VOLUME 2 8. PLANT FAMILIES AND THEIR DISPERSED POLLEN AND SPORE AFFINITIES 270 9. POLLEN AS A STRATIGRAPHIC TOOL IN THE TERTIARY 288 9.1 The dating of Oligocene deposits within the British Isles 295 9.2 Stratigraphic age of the studied sections 304 9.3 Reworked taxa 310 9.4 Application of form-generic groups to stratigraphic resolution 311 10. LATE PALAEOGENE PALAEOCLIMATE 314 10.1 Palaeogene palaeoclimate and the Eocene-Oligocene transition 314 10.2 Vegetational and palaeoclimatic changes in Britain and other areas of west em Europe during the Eocene-Oligocene transition. 318 11. PALAEOECOLOGICAL INTERPRETATION 322 11.1 Application of form-generic groups to palaeoecological interpretation 322 11.2 Lithofacies control on palynomorph assemblages 327 11.3 Peat formation and wetland ecology 328 11.3.1 Terminology applied to mire ecosystems 330 11.3.2 Autochthonous peat formation 332 11.4 Palaeoenvironment related to lithological character 335 12. PALYNOFLORAL INTERPRETATION 337 12.1 Lignite 337 12.2 Relative pollen abundance 340 12.3 Pollen preservation 340 12.4 Lough Neagh Group clays 341 12.5 Dunaghy Formation 341 13. PALAEOCLIMATE DETERMINATION 343 14. BOREHOLE CORRELATION 352 14.1 Correlation of sections using pollen and spore assemblages 352 15. CONCLUSIONS 354 15.1 Stratigraphy 354 15.2 Palaeoenvironment 354 15.3 Palaeoclimate 355 15.4 Pollen classification and nomenclature 355 16. REFERENCES 356 17. PLATES 378 APPENDICES Appendix 1. Approximate pollen per gram data 379 Appendix 2. Full core descriptions of studied sections 380 ENCLOSURES Enclosure 1. 13/611 Landagivey No.1 % Abundance Histogram Enclosure 2. 13/603 Ballymoney No.1 % Abundance Histogram Enclosure 3.27/415 Upper Mullan No.1 % Abundance Histogram Enclosure 4. 36/4680 Deerpark No.2 % Abundance Histogram Enclosure 5. 13/611 Landagivey No.1 Stratigraphic Range Chart Enclosure 6. 13/603 Ballymoney No.1 Stratigraphic Range Chart . Enclosure 7.27/415 Upper Mullan No. 1 Stratigraphic Range Chart Enclosure 8. 36/4680 Deerpark No.2 Stratigraphic Range Chart Enclosure 9. 13/611 Landagivey No.1 % Abundance Familial Affinity Enclosure 10. 13/603 Ballymoney No. 1 % Abundance Familial Affinity Enclosure 11. 27/415 Upper Mullan No.1 % Abundance Familial Affinity Enclosure 12. 36/4680 Deerpark No.2 % Abundance Familial Affinity Enclosure 13. Correlation Panel SUMMARY Pollen and spore assemblages from the Oligocene Lough Neagh Group and Dunaghy Formation, Northern Ireland John Andrew Fitzgerald This study was initiated to solve a stratigraphic problem for the Geological Survey of Northern Ireland prior to the revision in 1997 of the 1:250000 map of the solid geology of Northern Ireland. An exploratory drilling programme carried out by the Survey in 1983/1984 revealed the existence of previously unknown Tertiary sediments north west of the Tow Valley Fault. The boreholes revealed a sequence of clays and lignites that were attributed to the Lough Neagh Group. These lay above an interbedded sequence of litho marge, pyroclastics and lacustrine deposits termed the Dunaghy Formation. The Geological Survey required an age to be assigned to this formation and it was proposed that the use of the preserved pollen and spore assemblages offered the best means for dating the sequence. In order to achieve this four boreholes were analysed. Boreholes 13/611, 13/603, 36/4680 and 27/415 contain the Lough Neagh Group. In addition 13/611 and 13/603 contain the Dunaghy Formation. From the pollen and spore assemblages recovered an Oligocene age IS confirmed for the Lough Neagh Group and proposed for the Dunaghy Formation. This information led to the attribution of an Oligocene age to the Dunaghy Formation in the 1997 revised 1:250000 Geological Map of Northern Ireland. The palaeovegetation deduced from the recovered pollen and spore assemblages is in accordance with an Oligocene cooling. The climax angiosperm vegetation, predominantly consisting of temperate forms with some megatherm taxa, grew in a raised bog forest ecosystem within a fluvial-lacustrine environment. All pollen and spore taxa recovered are described including new forms identified. A correlation of the four sections is proposed. ACKNOWLEDGEMENTS The writing of this thesis has been a protracted venture mostly completed during leisure hours. Work commenced in Sheffield supported by my duties preparing industrial samples in the palynological laboratory at the University. Upon obtaining a position as a palynologist with a petroleum consultancy, the work on this thesis continued at evenings and weekends. Many people have provided a variety of help and inspiration over the years of research and I would like to extend my thanks to them all. I would especially like to thank Dr. Ted Spinner and Dr. Duncan Mc Lean for their support throughout my time in Sheffield and their continued encouragement during my writing up period. My thanks are also extended to my supervisor Dr. David Jolley. I would like to express my gratitude to Dr. Guy Harrington, Mr. Paul Blanks, Mr. Tom Wilson, Miss Mary Wood and Mrs. Alison Buggins for invaluable help in the latter stages of this thesis. My thanks are also extended to my fellow laboratory workers for their moral support at all times and to Mr. Steve Ellin for technical advice. I take this opportunity to thank my wife for her understanding and patience throughout the first year of our marriage as my thesis has greatly preoccupied my attention and time. My last acknowledgement and expression of gratitude is to my parents who have been a cornerstone of support over the years. More recently they have given generously of their time in the proof reading of draft text. 1. INTRODUCTION In 1983/1984, the Geological Survey of Northern Ireland undertook an exploratory drilling programme that revealed the presence of previously unknown Tertiary sediments north west of the Tow Valley Fault. These sediments extended from Strano cum through Ballymoney to Agivey in Counties Antrim and Londonderry, Northern Ireland. The boreholes revealed a sequence of clays and lignites that were attributed to the Lough Neagh Group, well known from its extensive occurrence around Lough Neagh to the south. These sediments rested not upon fresh basalt but an interbedded sequence of lithomarge, volcanic acid tuffs, ashes, agglomerates and lacustrine sediments (comprising clay with Fe bands, occasional conglomerates, palaeo sol horizons and beds oflignites and lignitic clays). This interbedded sequence of lithomarge (a multicoloured, clay-based weathering product of the lavas), pyroclastics and lacustrine deposits was named the Dunaghy Formation. It was postulated that this sequence might have accumulated during the late Eocene. The problem facing the Geological Survey was to assign an age to these sediments for inclusion in the 1997 second edition 1:250000 Geological Map of Northern Ireland. As no other means of biostratigraphically dating the sequence was thought possible, it was suggested that an analysis of the preserved pollen and spore assemblages might help to achieve this aim. This research was undertaken in a response to the problem of dating the Dunaghy Formation. All pollen and spores identified from core samples have been described. For the purposes of classification within this study five new genera, six new 1 specIes and three new sub-species have been informally erected. Nine new combinations are proposed. Seven pollen and six spore informal types are described. The palynological assemblages obtained from the Lough Neagh Group and the Dunagy Formation, within boreholes 13/611 and 13/603 of the Ballymoney deposit, are compared with the Lough Neagh Group, from boreholes 27/415 from the Coagh region on the west shore of Lough Neagh, and 36/4680, from the Lough Beg area on the south east shore of Lough Neagh.

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