APPENDIX 1.
Geological setting of sediments dated to the Oligocene and Miocene of the northwest edge of Europe
Details concerning previous palynological investigations of exclusively Rupelian (section 1); exclusively Chattian (section 2), Oligocene (section 3), early Miocene (section 4) and sequences containing various ages (section 5) of the northwest edge of Europe have been described below. Descriptions of cores, boreholes and wells taken from sites, and their corresponding lithologies are listed. Dating methods applied to assemblages, proposed depositional settings, palaeoenvironmental reconstructions and palaeoclimate variable reconstructions, where possible, are described below for each study site.
APPENDIX 1.1.
Rupelian sites
Ballymacadam, Co. Tipperary, Republic of Ireland. The Ballymacadam assemblage was taken from pre-Quaternary sediment preserved in a 10 m-thick karstic infill, overlying 80 m of Carboniferous limestone, located in County Tipperary, Republic of Ireland (Wynne, 1857; Boulter, 1980; Coxon and Coxon, 1997; Coxon and McCarron, 2009). The sedimentology of the infill consisted of clays and biogenic material (Coxon and McCarron, 2009). The assemblage was used to reconstruct a well-drained, mixed woodland palaeoenvironment (Boulter, 1980). An Oligocene age was initially assigned to the site, based on the relative abundances of subtropical-tropical elements (Engelhardia and Arecaceae); this assignment was further refined to the Rupelian, based on the relative abundance of Rupelian-marker Boehlensipollis hohli (King et al., 2016).
Beacon Cottage Farm Outlier at St. Agnes Beacon, Cornwall. The St. Agnes Beacon (Beacon Cottage Farm Outlier) consists of two members including the lowermost, basal, and pebbly sand unit, the Basal Sand Unit and the overlying Candle Clay Unit (Davies and Kitto, 1878; Ussher, 1879; Jowsey et al., 1992). Lignite sample MR 10401, taken from the Candle Clay Member’s grey unctuous, laminated clays yielded microfloral remains (Atkinson et al., 1975; Walsh et al., 1987; Jowsey et al., 1992). The assemblage reconstructed a fern dominated assemblage, which thrived in a lacustrine subtropical palaeoenvironment (Walsh et al., 1987; Jowsey et al., 1992). Relative abundance of palms suggested winters were frost-free; mean annual lowland temperatures were reconstructed to 12°C (Walsh et al., 1987) This assignment was based on comparisons with assemblages of similar ages, taken from Bovey and Lough Neagh, from present-day and extinct comparisons of leaf physiognomic qualities of palms (Wolfe, 1978, 1979; Hubbard and Boulter, 1983; Walsh et al., 1987).
Bovey Basin. Bovey Basin contains <1200 m of post-Rupelian sequences of kaolinitic clays, sands and lignites which overlie Eocene flint gravels and Albian-Cenomanian shallow marine sands (Edwards, 1969, 1976). Rootlets were recovered from grey and brown silty clays near the Southacre Clay Pit from borehole 855754 (Edwards, 1976). Descriptions of floral remains from the Blue Water Mine deposits are listed by Heer (1862a-b), Reid and Reid (1910), Chandler (1957) and Wilkinson and Boulter (1980). The palynofloral assemblages reconstructed a frost-free palaeoenvironment with tropical to sub-tropical elements (Chaanda, 2016). Heer (1862a–b) retrieved samples from unnamed sections of the Bovey Tracey formation, though based on lithological descriptions of light-coloured quartzose sand and white clay beds and underlying brown clay sand lignite beds suggest samples were taken from the Blatchford Sands and the underlying Southacre Clay and Lignite (Vincent, 1974; Edwards, 1976; Huggett and Knox, 2006; Chaanda, 2016). White clay units were dominated by riparian elements and reconstructed a cold-peat moor (Heer, 1862a–b). Vegetation reconstructed around basins is dominated by marshlands and tree-covered slopes (Chandler, 1957). Bovey Basin was previously assigned a Chattian, based on the relative abundance of Boehlensipollis hohli, which has since been revised to a Rupelian age (Wilkinson et al., 1980; King et al., 2016). The “Tertiary” Bovey floral types were taken from the Heathfield, Brimley, Stover, Twinyeo, Southacre and Abbrook sections of the basin (Wilkinson and Boulter, 1980).
APPENDIX 1.2.
Chattian sites
Lough Neagh, Well 28 and the Lough Neagh Group. The post-Eocene Antrim Lava Group consists of basalts and rhyolites; the overlying Lough Neagh Group is relatively abundant with clays and lignite (McCann, 1991). The Oligocene deposits at Lough Neagh, Northern Ireland, were formed over the Palaeocene Antrim Lava Group (Parnell and Meighan, 1989). Deposits were made in a series of isolated sub-basins, which developed in regions influenced by subaerial volcanism, constrained by NE-SW strike-slip fault movements and by extensional (NNW-SSE) fault regimes (Parnell and Meighan, 1989). Furthermore, mudstones were retrieved from a claypit at Ballynakilly, Co. Tyrone; clays were found to contain many intrastratal microfaults, suggesting the Lough Neagh sediment was deposited under a syndepositional extensional regime (Parnell et al., 1989).
The Lough Neagh Group consists of four main lithologies: conglomerates; sandstones; mudrocks and lignites (Parnell et al., 1989). Conglomerate-types are found primarily in the sequence base; they contain basaltic clasts, including in situ regolithic basalt, chalk fragments and Carboniferous pebbles (Parnell et al., 1989; Fitzgerald, 1999). The Lough Neagh sandstones are both poorly and well-sorted; both types display crossing, low-angle laminations (Parnell et al., 1989; Fitzgerald, 1999). Poorly sorted sandstones contain fine-coarse grains with an angular texture within an abundant clay matrix, whereas well-sorted sandstones contain higher abundances of rounded and quartzose grains (Parnell et al., 1989). The mudstone and siltstone lithologies (mudrocks) are present in a variety of hues (inc. green, brown, black and grey) and contain plant root and biota remains (Parnell et al., 1989). Preserved gastropods - Viviparus lentus; Bernicia sp. and Unio sp. - are indicative of freshwater palaeoenvironments (Parnell et al., 1989). Lignite stratifications are interbedded within the lithologies; they are categorised into woody and non-woody types with woody-types containing <75% organic carbon (Parnell et al., 1989). Clays are dominantly pale-grey and bluish grey with sandy fractions, and high illite and kaolinite fractions - indicative of a non-marine sedimentary palaeoenvironment (Fitzgerald, 1999).
Pollen fossils retrieved from the Lough Neagh lignites suggest Lough Neagh’s Chattian palaeoenvironment contained a variety of ferns, palms, swamp cypress-types and conifers - indicative of warm-temperate autochthonous lake-margin swamps with frost-free palaeoenvironments (Wilkinson et al., 1980; Parnell et al., 1989; Parnell and Meighan 1989). Open lake deposits were also reconstructed for Lough Neagh, based on autochthonous assemblages (Parnell and Meighan 1989).
Boreholes taken from the edge of the Lough Neagh (see following sections) were assigned a Chattian age based on the assumption they were taken from the Chattian-dated Lough Neagh Clays (Fitzgerald, 1999). A Chattian was initially assigned to boreholes taken from the Lough Neagh Group, and the surrounding boreholes, being 13/611, 27/415, 13/603 and 36/4680 and Well 28 (Parnell et al., 1989; Hubbard and Boulter, 1980; Wilson, 1996; Fitzgerald, 1999; King et al., 2016). Sediment taken from Well 28 was deposited in a lacustrine depositional setting; lignitic sections were deposited in mudflat palaeoenvironments (Portlock, 1834; Parnell et al., 1989; Wilson, 1996).
Landagivey-1 (BH 13/611). The 13/611 borehole was taken from Landagivey (Lann Áth Geimhe) from County Londonderry, Northern Ireland. Fitzgerald (1999) took 31 samples from the Landagivey borehole at depths 265.65-47.00 m (13/611). The uppermost depths of the borehole contained thick bands of brown and black lignites, intermixed with clayey, fine-grained light to medium grey clays (Fitzgerald, 1999). Lignitic horizons contained <1 mm diameter white clasts (Fitzgerald, 1999). Depths 47.00-166.00 m were dominant in light bluish, grey, olive, and dark yellow clays (Fitzgerald, 1999). Lowermost depths of the 13/611 borehole (261.00-265.65 m) contained greenish-grey clays.
Ballymoney-1 (BH 13/603). Borehole 13/603 was taken from the Tow Valley Fault Line, and 16 samples were taken from depths 290.00-48.00 m (Fitzgerald, 1999). Its uppermost depths (48.00-161.19 m) were characterised by light grey and brownish clay lithologies and with occasional black and brown lignitic fragments (Fitzgerald, 1999). The Ballymoney basin lignites have a high V/Cr ratio, representative of low Cr concentrations, suggesting inorganic matter in the Ballymoney lignites was sourced from the weathering products of the corresponding basalt (Parnell et al., 1989).
Deerpark-2 (BH 36/4680). The Deerpark-2 borehole was sampled at 19 depths along the depths from 72.05-265.13 m (Fitzgerald, 1999). The uppermost clay sections of the Deerpark-2 borehole were described as dominantly yellow and brown with fine sandy clays. Black woody lignitic fragments were present at depths 103.62 m, and occasional olive colouring of clays was observed (Fitzgerald, 1999). The middle-most layers (233.18-250.00 m) contained brown to black lignitic and organic clays; some showed a notable bright lustrous shine. Layers up to depth 250.00 m contained patches of stiff, brown, and yellow clays. Lowermost depths (250.00-265.13 m) contained greenish, olive, and bluish-hued clays (Fitzgerald, 1999).
Upper Mullan-1 (BH 27/415). The Upper Mullan-1 borehole (27/415) is one of four boreholes (27/ 416; 27/417; 27/418) taken from the Coagh region, Northern Ireland (Parnell et al., 1989). The Coagh deposit lies on the top of the Antrim Lava Group, based on seismic surveys (Griffith et al., 1987; Fitzgerald, 1999). All four of the Coagh boreholes contain pollen-productive lithologies. In lignitic regions (<1 km-deep) contain many tricolpates and trilete-types (Parnell et al., 1989; Fawcett and Grimshaw, 1989). The Coagh boreholes are relatively uniform in their lithologies; lowermost layers contain mudrock and conglomerates, which are overlain by green mudrocks - which are plentiful in alete spores but limited in bisaccate pollen-types; uppermost green mudrocks contain the vice-versa in assemblage recovery (Parnell et al., 1989). Based on the report of Sequoia -types in the Coagh boreholes, the transition towards a drier-climate towards the later Chattian was proposed (Parnell et al., 1989).
APPENDIX 1.3.
Oligocene sites
Petrockstowe Basin, Devon. The Petrockstowe Basin overlies the Culm Measures, Devon, and is composed of sharply based red clays beds which contain spherulitic siderites (Bristow et al., 1992). The palaeobotanical remains found in the uppermost layers are comparable to the Bovey Basin assemblages, thus an Oligocene was assigned to the basin (Vincent 1974; Echlin 2009). Consistent with a post-Eocene assigned from carbon isotope excursions between depths 120-240 m (Chaanda, 2016). Examples of determinant genera include Arecipites, Monocolpopollenites, Inaperturopollenites, Pompeckjoidaepollenites (Chaanda, 2016). Petrockstowe Basin’s assemblage reconstructed a subtropical-tropical wetland palaeoenvironment (Turner, 1979; Chaanda, 2016).
Stanley Bank Basin. The Stanley Bank Basin is a half-graben adjacent to the Sticklepath-Lustleigh Fault Zone composed of three units with Palaeozoic bedrock, based on seismic survey and borehole results (Tappin et al., 1994). Stanley Bank Basin’s middle unit’s seismic character is represented by parallel reflectors and is composed of two main facies (King et al., 2016). The lower facies of the middle unit consist of a matrix of colour-mottled clay intermixed with carbonaceous debris (King et al., 2016). The upper facies of the middle unit contain lignitic beds (<5 m-thick), clay and laminations of interbedded silt (King et al., 2016). The Stanley Bank Basin was deposited on a coastal plain, with lignitic sections deposited on Rupelian alluvial floodplains and swamps; marine influence is evident but limited in sections, based on the relative abundance of microplankton (King et al., 2016). Both facies were assigned an Oligocene age, based on the diatoms found, the Alnipollenites verus- Symplocos vestibulum ratios (Chattian) and Boehlensipollis sp. (Rupelian) relative abundance in BGS borehole 73/36 (Boulter and Craig, 1979; Tappin et al., 1994; Evans et al., 1991). Relative abundances of microplankton Areoligera semicirculata imply a Rupelian-early Chattian age (Wilson, 1996; King et al., 2016). Facies age is assumed Rupelian at its lowest boundary, given similarities in lignite observed with the proximal Bovey Formation (Wilson, 1996; King et al., 2016).
Washing Bay. The Washing Bay Borehole (<600 m-thick) contains three distinct layers: the Upper Clay and Sand Unit (245 m-thick); the Middle Shales (38 m-thick) and the Lower Clays and Sands (58 m-thick) - which contains lignitic layers up to 2 m-thick, and dark fossiliferous material (Wilkinson et al., 1980). Macrofossil, dicotyledon leaf (Dewalquea -types), and freshwater mollusc remains (Unio and Viviparus -types) were recovered, but due to the poor condition of remains, palaeoenvironmental reconstructions attempts have been unreliable (Johnson and Gilmour, 1921, 1922; Wright, 1924; Johnson, 1941). Wilkinson et al. (1980) suggested sediment was deposited proximal to river deltas, and shallow lake systems (Manning et al., 1970; Watts, 1970). An Oligocene age is assigned to the Washing Bay borehole, based on the borehole’s proximity to other Oligocene basins taken from the Lough Neagh Group (Wilkinson et al., 1980; King et al., 2016).
Ballynakilly. The Ballynakilly borehole (31/1091) contains 31 m of Oligocene-dated light grey kaolinite-dominated, silty clays, which were taken from a site near Coalisland (Bain et al., 1976; Wilkinson et al., 1980). Where plant debris was present, clays were darker; ironstone nodules were reported in proximal clay pits (Wilkinson et al., 1980). The Ballynakilly assemblage reconstructed a woodland-wetland palaeoenvironment with very minor subtropical-tropical elements (Bain et al., 1976; Wilkinson et al., 1980). A broad “Oligocene-age” was assigned to the assemblage, based on the basin’s proximity to the Lough Neagh Group (King et al., 2016).
Ballygiblin, County Cork. The Ballygiblin assemblage, retrieved from a poorly productive red and grey clay deposit, was assigned an ?Oligocene age based on the relative abundance of Cicatricosisporites -type and the assemblage’s proximity to the Chattian Lough Neagh basin (Simms and Boulter, 2000; King et al., 2016). Based on the abundances of mosses and ferns, a humid, heavily vegetated palaeoenvironment, with proximity to a lowland stream, was reconstructed (Simms and Boulter, 2000).
Mire House. The Mire House borehole, Northern Ireland, penetrated the edge of the Oligocene Lough Neagh Clays, and it yielded a very limited assemblage (Fowler and Robbie 1961; Watts, 1962; McCann, 1991). The Mire House lignite bands were assigned an Oligocene-age, based on the borehole’s proximity to the Lough Neagh Group (Watts 1962; King et al., 2016).
Bellbrook. The Bellbrook borehole was taken from the east edge of the Lough Neagh Clays, and consists of thin, sandy horizons, representative of a low energy palaeoenvironment (Wilkinson et al., 1980). Whilst Bellbrook samples had limited pollen recovery, the Oligocene dominantly autochthonous assemblage reconstructed a woodland palaeoenvironment, with a forest-floor heathland population (Wilkinson et al., 1980; McCabe et al., 1987). A ?Chattian age was proposed for sediment (King et al., 2016).
APPENDIX 1.4.
Early Miocene sites
Castlemartin-3 borehole, Flimston Bay, Pembrokeshire. The Castlemartin-3 borehole was abundant in varicoloured mottled clays of white, red and brown hues (King et al., 2016). Palynological analysis of the Flimston Bay borehole yielded a limited assemblage; post-late Oligocene dating (estimated age 23.03-15.97 Ma) was assigned based on the relative abundance of Taraxacum sp. and a lack of Cicatricosisporites -types (Jenkins et al., 1995; McLean, 2002; King et al., 2016). The assemblage reconstructed a brackish-freshwater lake environment with a fluctuating lake margin, which was periodically colonised by low-level aquatic plants (McLean, 2002).
APPENDIX 1.5.
Sequences
Mochras. The Mochras borehole was drilled 3 km west of Llanbedr, North Wales, and was taken from a southeast-dipping half-graben (Boomer and Whatley, 1992; Holford et al., 2005). The lowermost depths of the post-Jurassic sediment (77.47-601.78 m) contain lignite, clays and silts dated to the Oligocene, with possible Miocene horizons at the uppermost layers (Woodland, 1971; Herbert-Smith, 1979; Dobson and Whittington, 1987; Tappin et al., 1994). The lowermost unit of the Cenozoic sequence was termed the Basal Red Group (441.0-601.78 m) and is defined by striking-red and structureless layers of silt, which had undergone extensive bioturbation regimes (Woodland, 1971; Herbert-Smith, 1979; Tappin et al., 1994). Silts are slickensided at a 70° angle, and iron banding throughout the member varies in length (Woodland, 1971; Herbert-Smith, 1979). The overlying unit, the Transitional Series (326.8-441.0 m) contains upwards fining sediment beds with clays and silts most prominent towards the upper layer sections (Herbert-Smith, 1971; Woodland, 1971). We do not consider the uppermost Lignite and Clay Unit, as its age is post-early Miocene (Herbert-Smith, 1971; Woodland, 1971; Tappin et al., 1994 King et al., 2016). Previous palynological work form the Mochras Borehole used 66 pollen samples to reconstruct a subtropical to warm-temperate palaeoenvironment with no dominance between moist or arid conditions inferred (Herbert-Smith, 1971). The relative abundances of Triatriopollenites rurensis and Triatriopollenites microcoryphaeus were used to assign a Rupelian-middle Miocene age to depths (Herbert-Smith, 1971).
Marine boreholes, North Sea. The associations in the marine sequences (16/16B-4 and 21/28B-7) were dated using the relative abundances of listed microplankton, dinoflagellate cyst and pollen-based biomarkers (Wilson, 1996; King et al., 2016). Ages were proposed for listed associations, based on the sea-level curve; proposed ages are listed in Table 2 and Figure 2 (Haq et al., 1987; Cande and Kent, 1995; Wilson, 1996).
Well 16/16B-4. Core 16/16B-4 was taken from the southern section of the South Viking Graben of the North Sea (Wilson, 1996). The 16/16B-4 sequence is comprised of ten associations; Associations A–C were dated to the Rupelian (>28.28 Ma), Associations D–F were dated to the Chattian (28.28-24.23 Ma) and an early Miocene age was proposed for Association G (Wilson, 1996). Oligocene sections contain micaceous, sandy-clayey siltstones, grey-brown claystones and calcareous sands. Brittle sections of lignite were dark brown to black in hue (Wilson, 1996). 7 assemblages were taken and labelled as Associations A–G. Associations were assigned to the Oligocene, based on the relative abundance of pollen-types, including Tricolpopollenites -types; Nyssa -types; Sciadopitys -types, amongst others (Wilkinson and Boulter, 1980; Wilson, 1996). Assemblages Associations A–C reconstructed an open marine palaeoenvironment (Wilson, 1996). A Rupelian assignment on the listed associations was based on the relative abundances of Aerosphaeridium arcuatum, A. actinocoronatum, Deflandrea phosphoritica, Distatodinium ellipticum, the top occurrence of Dicolpopollis kockeli (Association C), Pompeckjoidaepollenites subhercynicus, Phthanoperidinium alectrelophum, Retitricolpites anguloluminosus, Sparganiaceoepollenites polygonalis, Svalbardella cooksoniae, Wetzeliella gochtii, W. symmetrica and undefined species listed as Microdinium sp.1 (Châteauneuf, 1980) and Spiniferites sp.1 (Manum et al., 1989; Wilson, 1996).
Associations D–G were dated based on the first appearances of relative abundances of selected taxa, including but not limited to - Quercoidites microhenrici, Corrusporis tuberculatus, Corsinipollenites paradorogensis and Cicatricosisporites -types (Wilson, 1996). No changes in relative abundances of taxa were observed between the latest Oligocene and early Miocene sections (Wilson, 1996). An early Miocene age was assigned to Association G, based on the relative abundances of selected taxa, such as - Momipites -types, and increases in the relative abundance of Cupuliferoipollenites -types and Trivestibulopollenites -types (Wilson, 1996). Microplankton associations in the Chattian assemblages, taken from Associations D-F reconstructed shallower marine conditions, with a dominantly brackish palaeoenvironment (Châteauneuf, 1980; Brinkhuis, 1994; Wilson, 1996).
Well 21/28B-7. Core 21/28B-7 was taken from the Outer Moray Firth from the North Sea basin, and Oligocene sediment was present between depths 2770–3200 ft (Wilson, 1996). 7 assemblages were taken and were assigned to sections labelled as “associations” from 21/28B-7 Association A–G (Wilson, 1996). Oligocene layers contained grey and green layers of calcareous claystones and brown, sandy siltstones with micaceous, sandy patches (Wilson, 1996). Associations A–D were assigned a Rupelian age (>28.28 Ma), whereas Associations E–G were assigned a Chattian age (27.03–25.50 Ma) (Wilson, 1996). A hiatus was recorded after the top of Association D (Wilson, 1996).
Assemblages from Associations A–C reconstructed an open marine palaeoenvironment (Wilson, 1996). Marine biomarkers Apteodinium spiridoides, Areosphaeridium arcuatum, Areoligera semicirculata, Chiropteridium mespilanum, C. lobospinosum, C. partispinosum, Dapsilidinium simplex, Phthanoperidinium amoenum, P.comatum, P. filigranum, Rhombodinium draco Systematophora placacantha, Thalassiphora pelagica and Wetzeliella symmetrica were used to assign a Rupelian age to Associations A-C (Wilson, 1996). Unspecified species, Spiniferites sp. 1 (Manum et al., 1989) and Microdinium sp.1 (Châteauneuf, 1980) were also used to date Associations to the Rupelian (Wilson, 1996). Pollen-types Camerozonosporites haskemsis; Cicatricosisporites chattensis; Micrhystridium fragile; Porocolpopollenites vestibulum; Retitricolpites retiformis; Stereisporites (Stereisporites) stereoides and Tricolporopollenites spinus were used to support a Rupelian assignment (Wilson, 1996). The assemblages from Associations E-G reconstructed a marine palaeoenvironment with proxies deposited in a shallow, near-shore basin (Islam, 1983; Brinkhuis, 1994; Wilson, 1996). A Chattian age was assigned to Associations E–G, based on the relative abundances of Verrucatosporites alienus, V. balticus and Echinosporis echinatus -types and comparisons with the sea-level curve (Haq et al., 1987; Cande and Kent, 1995; Wilson, 1996).
Borehole 80/14, Little Minch Basin, Isle of Skye (57.77°N, 6.92°W). Borehole 80/14 was taken from the west section of the Minch Fault, and it penetrated through 34.6 m and 44.4 m of Quaternary and Oligocene sediments, respectively (Wilson, 1996). The 80/14 borehole was split into 8 associations- Associations A-C were assigned to the Rupelian, Associations D–H were assigned to the Chattian (<28.28 Ma) (Wilson, 1996).
The Little Minch Basin is a small half-graben which lies along the Minch Fault in Scotland (Fyfe et al., 1993; King et al., 2016; Fyfe et al., 2021). The basin’s lithology contains plant debris (in core 80/14), poorly sorted interbedded sandstone layers and kaolinitic and carbonaceous clays with occasional allochthonous lignite layers (O’Sullivan, 1979; Wilson, 1996; King et al., 2016). The borehole’s lithology is dominated by grey, fossiliferous claystones and carbonaceous fragments (Wilson 1996). Lignite bands (0.1–1 m-think) were present throughout depths 60–80 m; layers of conglomerates and grit were recorded at respective depths 71.6 m and 75.5 m (Wilson, 1996).
The Rupelian-dated associations of the 80/14 borehole (depths 78.93–77.00 m, Associations A–C) are dominantly comprised of layers of grey claystone (Wilson, 1996). A Rupelian age was assigned to Associations A–C, based on the base occurrence of Verrucatosporites alienus and V. histiopteroides (Wilson, 1996). A Chattian age was assigned to Associations D–E, based on the relative abundance of Cicatricosisporites chattensis and Cyrillaceaepollenites megaexactus, respectively (Wilkinson and Boulter, 1980; Vinken, 1988; Wilson, 1996). The Little Minch assemblage from borehole 80/14 was dated to the Chattian, based on the relative abundances of Alnipollenites verus and Symplocos vestibulum, but this was further refined with reference to more stratigraphic taxa-types, as assemblages from Association F–H were comparable with Chattian assemblages from core 16/16B-4, thus were also assigned to the Chattian (Wilson, 1996). Material was deposited in a non-marine, alluvial floodplain palaeoenvironment (Evans et al., 1991). The Little Minch pollen records reconstructed a freshwater fen palaeoenvironment, based on the relative abundance of Alnipollenites verus and Verrucatosporites histiopteroides, and a proximal conifer-surrounded wetland (Evans et al., 1991; Wilson, 1996).
Borehole 88/12 (57.78°N, 7.00°W). The Oligocene section of the 88/12 borehole consists of conglomerates, interbedded laminations of siltstones and mudstones, alongside sections of lignite (Wilson, 1996). The 88/12 sequence was split into 7 associations; a Rupelian age was assigned to Associations A–C (>28.28 Ma), and a Chattian age was assigned to Associations D–H (28.28–24.23 Ma).
Rupelian-dated associations of the 88/12 borehole (depths 48.50–41.70 m) contains sands with conglomerates at lowermost depths, and sands with pebble clasts (Wilson, 1996). Uppermost Rupelian layers contain thin bands of lignite, held within layers of sands and conglomerates (Wilson, 1996). Rupelian-dating of Associations A–C was based on the relative abundance of Laevigatosporites discordatus and one algae-type (sp.1); assemblages were comparable to those described in the Rupelian-dated Association B in borehole 21/28B-7 (Wilson, 1996). The recovered palynological assemblage was limited, but Associations D–G were assigned to the Chattian, based on the relative abundance of Trivestibulopollenites betuloides; Cupuliferoipollenites cingulum -types; the top appearance of Arecipites -types (Wilson, 1996).
Borehole 78/01, Canna Basin (57.14°N, 6.75°W). The 78/01 borehole was taken from Canna Basin, which overlies the Little Minch Trough, located in the Sea of Hebrides (Smythe and Kenolty, 1975; Evans et al., 1979; Wilson, 1996). The Canna Basin (<20 km in length) infills a downwarped section of Paleocene basalts (Smythe and Kenolty, 1975; Evans et al., 1979; Fyfe et al., 1993). Its Oligocene section (where depths < 1091.18 m) is comprised of dark-green and lignite-containing layers of brown claystones; layers of coarse sand, grit and pebbled beds are present in the uppermost sections (Wilson, 1996; King et al., 2016). Samples were taken from 7 sections, split into Associations; Associations A–B and Associations C–G were assigned to the Rupelian and Chattian, respectively (Wilson, 1996). Sediment was deposited in non-marine, lacustrine to brackish palaeoenvironmetal settings (Evans et al., 1979; Wilson, 1996; King et al., 2016).
Rupelian-dated depths in the 78/01 borehole (141.20–139.57 m) are comprised of green-brown claystone layers (Wilson, 1996). A Rupelian age-assignment to borehole 78/01 was based on the relative abundance of biomarkers Cicatricosisporites chattensis; Cupuliferoipollenites cingulum subsp. pusillus and the base occurrence of Favitricolporites microreticulatus (Wilson, 1996). Associations C–G were assigned to the Chattian, based on the assemblage comparisons with Chattian-associations of cores 16/16B-4, 77/07 and 88/12, where Quercoidites microhenrici, Verrucatosporites megabalticus and Graminidites -types were present (Wilkinson and Boulter, 1980; Wilson, 1996).
Borehole 77/07, Solan Bank High, Rona Basin (59.34°N, 4.95°W). Borehole 77/07 was taken from the northwest edge of the Solan Bank High, from its Oligocene-Miocene post-rift drape, which overlies subsided sections of Jurassic-Paleocene infills (Evans et al., 1991; Wilson, 1996). The 77/07 was sampled in five different sections, and assemblages were labelled to have been derived from Associations A–E, respectively (Wilson, 1996). Association A, Association B–D and Association E were dated to Rupelian, Chattian and an early Miocene age, respectively (Wilson, 1996). Hiatuses were recorded in Associations B and D (Wilson, 1996).
The Rupelian-dated association of the 77/07 borehole is dominantly comprised of fine-grained sand, containing vertical rootlets (Wilson, 1996). Assemblages were taken from 5 Associations from borehole 77/07. Association A was dated to the Rupelian, and Associations B–D were assigned to the Chattian; Association E was assigned an early Miocene age (Wilson, 1996). Association A was assigned a “Middle-Oligocene”/ Rupelian, based on the base occurrences of Triatriopollenites rurensis, Tricolporopollenites pseudocingulum and similarities in assemblages with those established by 21/28B-7 (Association D), 88/12 (Association B) and those listed by Wilkinson and Boulter (1980); Vinken (1988) (Wilson, 1996). The Mudstone Unit (110.2–112.2 m) was dated to the Oligocene, based on the relative abundance of Chattian markers, including Favitricolporites microreticulatus, Polyatriopollenites carpinoides, Graminidites annulatus, Gothanipollis gothanii and Quercoidites microhenrici (Châteauneuf, 1980; Vinken, 1988; Wilson 1996). Assemblages were comparable with the Chattian units in 16/16B-4, 21/28B-7 and 80/14 (Wilson, 1996). The Mudstone Unit contained fossiliferous layers of siltstones and dark carbonaceous claystones (Wilson, 1996). The overlying Carbonaceous Unit (112.5–125.3 m) contains highly carbonaceous sandstones and sulphurous, yellow layers of lignite (Wilson, 1996). Association E was dated with an early Miocene age, based on the relative abundance of Aa1 biozone dinoflagellate cyst markers (Spiniferites ramosus, Systematophora placacantha and Paralecaniella indentata) (Powell, 1992; Wilson, 1996), although based on the presence of the listed dinocyst-types, its true age could overlap with the southern North Sea Miocene zones 1–9, being latest-Chattian to earliest Tortonian (Munsterman and Brinkhuis, 2004). Early Miocene sections contained fossiliferous dark-green, sandy siltstones and layers of mudstone and sandstone (Wilson, 1996). The layers between Oligocene-Miocene-dated sediment are composed of silty, buff mudstone (Wilson, 1996).
Stanley Bank Basin (73/36). The Stanley Bank Basin is a half-graben adjacent to the Sticklepath-Lustleigh Fault Zone composed of three units with Palaeozoic bedrock, based on seismic survey and borehole results (Tappin et al., 1994). Stanley Bank Basin’s middle unit’s seismic character is represented by parallel reflectors and is composed of two main facies (King et al., 2016). The lower facies of the middle unit consist of a matrix of colour-mottled clay intermixed with carbonaceous debris (King et al., 2016). The upper facies of the middle unit contain lignitic beds (<5 m-thick), clay and laminations of interbedded silt (King et al., 2016). Wilson (1996) dated 10 sections/ associations of the 73/36 borehole, with Associations A–D and Associations E–J, being Rupelian and Chattian, respectively (Wilson, 1996). A hiatus was recorded between Associations D and E (Wilson, 1996).
Rupelian-dated associations A-D (depths 33.10-20.09 m) of the 73/36 borehole contains brown, laminated claystones, sandy siltstones and grey sands at lowermost depths (Wilson, 1996). Uppermost layers contain a frequently varying sedimentology. Layers contain laminated, waxy claystones, red sandstones, orange siltstones and occasional rootlets (Wilson, 1996). Associations A-D were dated to the Rupelian based on the relative abundances of Dicolpopollis kockeli (Association A); Corrusporis tuberculatus; C. granotuberculatus; Reevesiapollis triangulus; Trivestibulopollenites betuloides; Verrucatosporites balticus; V. favus; V. histiopteris (Wilson, 1996). Rupelian ages were also assigned based on the base occurrences of Camerozonosporites heskemensis; Graminidites -types; Tricolporopollenites pseudocingulum and Triletes multivallatus and the first appearances of Tricolporopollenites baculoferus in the pollen records (Wilson, 1996).
The Stanley Bank Basin was deposited on a coastal plain, with lignitic sections deposited on Rupelian alluvial floodplains and swamps; marine influence is evident but limited in sections, based on the relative abundance of microplankton (King et al., 2016). Relative abundances of microplankton Areoligera semicirculata imply a Rupelian-early Chattian age (Wilson, 1996; King et al., 2016). Facies age is assumed Rupelian at its lowest boundary, given similarities in lignite observed with the proximal Bovey Formation (Wilson, 1996; King et al., 2016).
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APPENDIX 2.
List of pollen types (with revised taxonomy) reported throughout Oligocene to Miocene palynological study of the British Isles, presented in a presence-absence matrix. Synonyms are listed, dependent on row number, shown in column: identification (ID). Nearest Living Relatives (NLRs) are listed, where possible, based on assignments listed by Stuchlik et al. (2001, 2002, 2009, 2014) and Utescher et al. (2024). Available as a download.
APPENDIX 3.
Taxonomic revision of fossil names, based on revisions by Stuchlik et al. (2001, 2002, 2009, 2014). Available as a download.
APPENDIX 4.
List of model outputs of palaeoclimate variables from each study site. Reconstructed optima and 50% uncertainties and the differences between optima and uncertainties have been listed. Available as a download.
