Figures and tables

Figures

(Figure 1.1) Location of Caledonian intrusive and extrusive igneous rocks of Great Britain relative to areas affected by Caledonian deformation and major terrane boundaries. Based on Brown et al. (1985). Nomenclature of terranes simplified after Gibbons and Gayer (1985), Bluck et al. (1992) and British Geological Survey (1996).

(Figure 1.2) Stratigraphical distribution of Caledonian extrusive rocks (solid bars) and intrusions (open bars) in the various terranes of the British Caledonides. The timescale is after Harland et al. (1990); horizontal lines indicate descriptive time units as used in the main text. Wherever possible the extrusive rocks are plotted according to their biostratigraphical range, as are the intrusions of Wales. Other intrusions have little or no biostratigraphical control and hence are plotted according to their currently accepted radiometric ages. This leads to some unavoidable discrepancies, in particular in the upper Silurian to Lower Devonian suites of Scotland, where intrusions and volcanic rocks in the same area are probably much closer in age than the diagram shows (see Chapter 9, Introduction). See individual chapter introductions for more detailed stratigraphical distribution charts.

(Figure 1.3) Reconstructions of the movements of continents bordering the Iapetus Ocean and Tornquist Sea during the Caledonian Orogeny. (a) and (b) are broad 'views' that are neccessary to encompass the great width of the ocean during the early stages of the orogeny. Note the separation of Avalonia from Gondwana during this time. Adapted from Torsvik et al. (1992) by Trench and Torsvik (1992). (c), (d) and (e) show the later stages of the orogeny in more detail, with progresssive narrowing of the oceanic areas, convergence of the continents and ultimate continent—continent collisions and strike-slip re-alignment of terranes. Adapted from Soper et al. (1992).

(Figure 2.1) A pre-Atlantic reconstruction of the Caledonian Orogen showing the positions of the principal ophi-olite complexes. A location map for the Scottish examples is shown inset.

(Figure 2.2) An idealized ophiolite succession compared to the seismic structure of oceanic crust and mantle (after Coleman, 1977). As an indication of scale, beneath the oceans the depth to the geophysical moho is between 5 and 10 km.

(Figure 2.3) Descriptive nomenclature for ultramafic rocks in terms of their relative content of olivine and pyroxene.

(Figure 2.4) Maps of the Shetland Ophiolite (after Flinn, 1996): (a) principal tectonic units, (b) lithological outcrops. GCR sites: 1, The Punds to Wick of Hagdale; 2, Skeo Taing to Clugan; 3, Qui Ness to Pund Stacks; 4, Ham Ness; 5, Tressa Ness to Colbinstoft; 6, Virva.

(Figure 2.5) Outline geology of the Ballantrae Complex (after Stone and Smellie, 1988) showing the location of the GCR sites. 1, Byne Hill; 2, Slockenray coast; 3, Knocklaugh; 4, Millenderdale; 5, Knockormal; 6, Games Loup; 7, Balcreuchan Port to Port Vad; 8, Bennane Lea; 9, Sgavoch Rock.

(Figure 2.6) Map of the Wick of Hagdale area, Unst.

(Figure 2.7) Rhythmic banding in the metaharzburgitc at The Viels [HP 6444 1108] close to the petrological Moho. The hammer is 37 cm long. (Photo: D. Flinn.)

(Figure 2.8) Map of the Skeo Taing area, Unst.

(Figure 2.9) Rhythmic banding in metagabbro [HP 647 077]. (Photo: D. Flinn.)

(Figure 2.10) Map of the Qui Ness area, Unst.

(Figure 2.11) Closely spaced, parallel metabasic sheets of the quasi-sheeted-dyke complex at Pund Stacks, Unst [HP 6218 0340]. (Photo: D. Flinn.)

(Figure 2.12) Map of Ham Ness and Mu Ness, Unst.

(Figure 2.13) The Mu Ness serpentinite klippe (dark coloured) resting on lower metagabbro of the lower nappe (light coloured) as seen from [HP 637 000]. (Photo: D. Flinn.)

(Figure 2.14) Map of the Stackaberg to Tressa Ness area, Fetlar.

(Figure 2.15) Tressa Ness from the south showing the sheared antigoritized harzburgite (dark colour) and the unsheared lenses of antigoritized dunite (light colour). (Photo: D. Flinn.)

(Figure 2.16) (a) Map of the Virva area, Fetlar. (b) cross section

(Figure 2.17) Virva from the north, showing the outcrop of the thrust below the Upper Nappe and the underlying homblendic rocks. NHS, Norwick Hornblendic Schist (Photo: D. Flinn.)

(Figure 2.18) Map of the Garron Point to Slug Head area, Stonehaven. Based on BGS 1:10 000 Sheet NO88NE (1996).

(Figure 2.19) The Highland Border Complex at Slug Head and Garron Point looking SW towards Stonehaven. (Photo: C.W. Thomas.)

(Figure 2.20) Map of the Balmaha and Arrochymore Point area (after Henderson and Fortey, 1982; Bluck, 1992).

(Figure 2.21) Looking SW from Conic Hill across Loch Lomond. Druim nam Buraich (foreground, right of centre) shows exposures of the southern serpentinite belt. (Photo: BGS no. D5406.)

(Figure 2.22) Map of the North Glen Sannox GCR site, in part after Johnson and Harris (1967) and Anderson and Pringle (1944).

(Figure 2.23) North Sannox Burn below the road bridge, a section through the lower part of the Highland Border Complex. (Photo: Nature Conservancy Council.)

(Figure 2.24) Map of the Byne Hill area (after Bloxam, 1968).

(Figure 2.25) Map and stratigraphy of the Pinbain Block, the northernmost part of the Ballantrae Complex, after Bluck (1982) and Stone and Smellie (1988). * The area marked thus on the map was included within the Pinbain Formation by Bluck (1982), but is more closely related lithologically to the Kilranny Hill Formation.

(Figure 2.26) Map of Bonney's Dyke, after Bluck (1992). See Figure 2.25 for location.

(Figure 2.27) Textural variation in the Bonney's Dyke pegmatitic gabbro between plagioclase (pale) and pyroxene (dark). The long axis of the sample is 170 mm. (Photo: BGS no. MNS4007.)

(Figure 2.28) Map of the SW margin of the Pinbain olistostrome, after Bluck (1978a, 1992). See Figure 2.25 for location.

(Figure 2.29) Massive, porphyritic basalt lava at Slockenray [NX 1403 9197]. The pale feldspar phenocrysts are tabular and range up to 2 cm in length. (Photo: BGS no. D4239.)

(Figure 2.30) Map of the metamorphic aureole developed adjacent to serpentinite at Knocklaugh, after Treloar et al (1980).

(Figure 2.31) Photomicrographs illustrating textures seen in 'beerbachite' dykes near Millenderdale: (a) Polygonal, granoblastic texture developed between feldspar and brown amphibole. Plane polarized light, x40. (Photo: BGS no. PMS469); (b) Development of mafic and leucocratic domains. Plane polarized light, x20. (Photo: BGS no. PMS470.)

(Figure 2.32) Map of the fault zone between Knockormal and Carleton Mains after BGS (1988).

(Figure 2.33) Map of the Games Loup area, after BGS 1:25 000 special sheet, Ballantrae (1988) and unpublished data.

(Figure 2.34) Green serpentinite veins cutting a red serpentinite host at Games Loup. Chrysotile veinlets are developed parallel to the vein margins. (Photo: BGS no. D3345.)

(Figure 2.35) Map of the Balcreuchan Port to Port Vad area, after BGS 1:25 000 special sheet, Ballantrae (1988) and Stone and Smellie (1988).

(Figure 2.36) Large, well-formed pillows of reddened, plagioclase-phyric basalt exposed SW of Balcreuchan Port. (Photo: BGS no. D3585.)

(Figure 2.37) Volcaniclastic breccia of aphyric and vesicular lava clasts from Bennane Head. The long axis of the sample is 165 mm. (Photo: BGS no. MNS3838.)

(Figure 2.38) Geochemical discrimination diagrams for Ballantrae Complex basalt lavas: (a) Ti—Zr—Y, fields from Pearce and Cann (1973). (b) Cr—Y, showing comparison with representative boninites after Smellie and Stone (1992); fields from Pearce (1982).

(Figure 2.39) Map of the Bennane Lea area, after BGS 1:25 000 special sheet, Ballantrae (1988) and Stone and Smellie (1988).

(Figure 2.40) Slump fold in chert interbedded with conglomerate and volcaniclastic sandstone at Bennane Lea. (Photo: BGS no. D3333.)

(Figure 2.41) The position of the Sgavoch Rock GCR site within the Downan Point Lava Formation and its relationship to the Ballantrae Complex and the Southern Uplands Terrane.

(Figure 2.42) A spectacular array of pillow lavas from the Downan Point Lava Formation exposed on the coast adjacent to the offshore Sgavoch Rock. The lavas are steeply inclined and slightly overturned. (Photo: BGS no. D1572.)

(Figure 3.1) Location of basic intrusions and late Caledonian granitic intrusions in the NE Grampian Highlands, modified after Ashcroft et al. (1984) by Gould (1997). GCR sites: 1, Hill of Barra; 2, Bin Quarry; 3, Pitscurry and Legatesden quarries; 4, Hill of Johnston; 5, Hill of Craigdearg; 6, Balmedie Quarry; 7, Towie Wood; 8, Craig Hall.

(Figure 3.2) Map of the Insch, Boganclogh and Kennethmont intrusions, adapted from Gould (1997). GCR sites: CH Craig Hall; HB Hill of Barra; HC Hill of Craigdearg; HJ Hill of Johnston; PL Pitscurry and Legatesden quarries.

(Figure 3.3) Typical landscape of the Insch intrusion. View WNW from Candle Hill, Oyne towards the 'Red Rock Hills'. Foreground rocks are norites of the Middle Zone. (Photo: W.J. Wadsworth.)

(Figure 3.4) Petrographical divisions and variation of mineral compositions in the Insch, Boganclogh and Belhelvie intrusions, from Gould (1997). Data from Ashcroft and Munro (1978), Gould (1997), Styles (1994) and Wadsworth (1986, 1988, 1991).

(Figure 3.5) Geological map of the area around the Hill of Barra GCR site, Insch intrusion, from Ashcroft and Munro (1978) and BGS 1:10 000 sheets NJ72NE (1989) and NJ82NW (1989).

(Figure 3.6) Map of the southern part of the Huntly–Knock intrusion, from BGS 1:50 000 Sheet 86W (in press), with details of the Bin Quarry GCR site, from Gunn and Shaw (1992).

(Figure 3.7) Layered olivine-gabbro cumulates of the Huntly intrusion Lower Zone in the Bin Quarry. Layering dips at 50° to the NW but modal layering, 'sedimentary' structures and variations in mineral composition show that the sequence 'youngs' to the SE and hence is inverted. (Photo: BGS no. D4122.)

(Figure 3.8) Block of layered olivine-gabbro cumulate of the Huntly intrusion Lower Zone in the Bin Quarry. The layering, which is inverted in this photograph, reflects both modal and mineral compositional variation, ranging from peridotite, through mafic gabbro and troctolite to anorthosite. (Photo: BGS no. D4121.)

(Figure 3.9) Map of the area around Legatesden and Pitscurry quarries, Insch intrusion, from BGS 1:10 000 Sheet NJ72NW (1989).

(Figure 3.10) Norite of the Middle Zone, Insch intrusion, intruded by a 10 m-thick sheet of pegmatitic granite with narrow veins branching off the main sheet, Pitscurry Quarry Pitcaple. (Photo: BGS no. D4332.)

(Figure 3.11) Map showing the location of the principal 'Red Rock Hills' (UZb and UZc of the Insch intrusion), west of Insch, from BGS 1:50 000 Sheet 76W (1993).

(Figure 3.12) The 'Red Rock Hills': Hill of Christ's Kirk (left distance) and Hill of Dunnideer (centre distance, with ruined castle) from near Auchleven. The hills are composed of syenite and olivine monzonite and the foreground is underlain by olivine-ferrogabbros, all of the Upper Zone, Insch intrusion. (Photo: BGS no. D4542.)

(Figure 3.13) Map of the Hill of Creagdearg and Red Craig area, Boganclogh intrusion, from BGS 1:10 000 sheets NJ42NW (1991) and NJ42NE (1991).

(Figure 3.14) Fresh peridotite (dunite) with brown-weathering crust, Red Craig, Boganclogh intrusion. (Photo: BGS no. D4532.)

(Figure 3.15) Map of the northern part of the Belhelvie intrusion, showing the position of the Balmedie Quarry GCR site in relation to a major shear zone, after Boyd and Munro (1978).

(Figure 3.16) Balmeddie Quarry; block of deformed mafic rock, cut by narrow zones of mylonite that in part conform with and in part transgress an earlier foliation. Scale in centimetres. (Photo: from Boyd and Munro, 1978, plate 1a.)

(Figure 3.17) Map of the area around the Towie Wood GCR site, Arnage-Haddo intrusion, from BGS 1:10 000 Sheet NJ93NW (1986) by W Ashcroft and M. Munro, Aberdeen University

(Figure 3.18) Map of the area around the Craig Hall GCR site, Kennethmont, from unpublished BGS maps.

(Figure 4.1) Lower Palaeozoic inliers of northern England and locations of the major, buried batholiths. Exposed granitic intrusions: En, Ennerdale; Es, Eskdale; Sh, Shap; Sk, Skiddaw; Th, Threlkeld; D Dufton.

(Figure 4.2) Lower Palaeozoic geology of the Lake District inlier showing the location of the GCR sites. 1, Eycott Hill; 2, Falcon Crags; 3, Ray Crag and Crinkle Crags; 4, Sour Milk Gill; 5, Rosthwaite Fell; 6, Langdale Pikes; 7, Side Pike; 8, Coniston; 9, Pets Quarry; 10, Stockdale Beck, Longsleddale; 11, Bramcrag Quarry; 12, Bowness Knott; 13, Beckfoot Quarry; 14, Waberthwaite Quarry; 15, Carrock Fell; 16, Haweswater; 17, Grainsgill; 18, Shap Fell Crags.

(Figure 4.3) The Scafell Caldera: within the caldera, thick sheets of welded silicic ignimbrite are overlain by caldera-lake sedimentary rocks. These are well displayed here in the Scafell Syncline, a structure that formed by Early Devonian tectonic compression of the Ordovician downsag caldera. In the crags on the left of the skyline the rocks dip to the right, and on the right the lacustrine rocks exposed in the pointed peak of Bowfell dip to the left. The bedded rocks in the foreground are breccias avalanched from local volcanotectonic faults during caldera collapse. (Photo: BGS no. D4031.)

(Figure 4.4) Summary chart of Lake District Caledonian igneous rocks. Bold numbers are GCR sites (numbers as per Figure 4.2). Radiometric dates: diamonds U-Pb; circles Rb-Sr; squares K-Ar; see text for sources. lo error bars are shown. Period of deformation and cleavage formation from Merriman et al. (1995). CFC Carrock Fell Complex; SKG Skiddaw Group. *Note: In the northern Lake District the base of the Windermere Supergroup is at the base of the Drygill Shale Formation; in the central/southern Lake District the base of the supergroup coincides with the base of the Dent Group (Kneller et al., 1994).

(Figure 4.5) Exposure map of Eycott Hill (from Millward and Molyneux, 1992).

(Figure 4.6) Pyroxene-plagioclase-megaphyric ('Eycott-type') basaltic andesite, Eycott Volcanic Group. The coin is 25 mm diameter. (Photo: BGS no. A6605.)

(Figure 4.7) Eycott Hill: craggy scarp and dip-slope topography of the Eycott Volcanic Group in the foreground, contrasted with smooth, regular scarps in the overlying Carboniferous Limestone in the background. View looking NE. (Photo: BGS no. A6616.)

(Figure 4.8) Falcon Crag (left) and Brown Knotts showing the terraced, trap-like topography of lavas and interbedded volcaniciastic rocks. (Photo: B. Beddoe-Stephens.)

(Figure 4.9) Map of the Falcon Crag GCR site.

(Figure 4.10) Generalized vertical section of Borrowdale Volcanic Group rocks between Brown Knotts and Bleaberry Fell; Falcon Crag GCR site.

(Figure 4.11) Simplified map of the Ray Crag and Crinkle Crags GCR site (mapping by M. J. Branney, 1988b).

(Figure 4.12) Generalized lithostratigraphy of the Scafell Caldera succession (after Branney and Kokelaar, 1994a).

(Figure 4.13) Field sketch of Oxendale and Crinkle Crags, viewed from the east, showing complex extensional faulting in an area separating caldera-floor rocks in the centre and right of the picture from sub-horizontal pre-caldera strata on the left (from Branney, 1995). BST, Bad Step Tuff; CT, Crinkle Tuffs; LTT, Long Top Tuffs; OX, Oxendale Tuff; Wig, Whorneyside ignimbrite; WPT, Whorneyside phreatomagmatic tuff.

(Figure 4.14) Field sketches of a volcanotectonic fault at Isaac Gill, viewed facing SW Inset (a) gives details of disrupted bedded tuff of the Whorneyside Formation within the fault zone. Inset (b) shows homogenized tuff along one of the many slide surfaces in the bedded tuff with footwall pull-apart structures and locally derived intraclasts. Slumped bedded tuff dips steeply towards the downthrow side of the main fault. Inset (c) shows mixing of blocks of ignimbrite and homogenized tuff (from Branney and Kokelaar, 1994a).

(Figure 4.15) Schematic summary of the evolution of the Scafell Caldera by piecemeal collapse. The cartoons are simplified and not to scale. (a) Emplacement of the Whorneyside ignimbrite across low-profile andesite volcanoes. (b) Proximal subsidence facilitates aqueous inundation of the vent, changing the eruption style to phreatoplinian (see the Sour Milk Gill GCR site report). (c) Onset of widespread piecemeal subsidence, deformation of Whorneyside phreatomagmatic tuff deposits and burial under hot silicic ignimbrites of the Long Top Tuffs erupted from new vents. (d) Continued subsidence with ductile deformation of hot ignimbrites and collapse of growing fault scarps. (e) Final stages of the paroxysmal eruption of the Crinkle Tuffs. (f) Caldera lake formation with deposition of subaqueous volcaniclastic sediments, along with post-collapse silicic dome emplacement (see the Rosthwaite Fell GCR site report) (from Branney and Kokelaar, 1994a).

(Figure 4.16) Sour Mill Gill from Seathwaite Farm, Borrowdale. Southward-dipping proximal lacustrine Whorneyside phreatomagmatic tuff (centre of the picture), intruded by andesite sills (right) is overlain by silicic ignimbrites of the Airy's Bridge Formation (left). (Photo: M. J. Branney.)

(Figure 4.17) Simplified map of Sour Milk Gill (after Kokelaar, in Kokelaar and Branney, 1999).

(Figure 4.18) Rosthwaite Fell, from the village of Rosthwaite, Borrowdale. (Photo: D. Millward.)

(Figure 4.19) Map of Rosthwaite Fell, Borrowdale (based on mapping by B. P Kokelaar, B. C. Kneller, N. Davies and M. J. Branney, for British Geological Survey).

(Figure 4.20) The Langdale Pikes, viewed from the south. Welded ignimbrites within the Scafell Caldera form the lower crags and Gimmer Crag (top left of centre). Pyroclastic and sedimentary rocks of the caldera-lake succession are well exposed on Pike of Stickle (far left) and Harrison Stickle (right of centre). (Photo: D. Millward.)

(Figure 4.21) Map of the Langdale Pikes, Great Langdale (based on mapping by M. J. Branney, B. J. McConnell and B. C. Kneller, for British Geological Survey).

(Figure 4.22) Pavey Ark breccia from the top of Pavey Ark. Rag-shaped clasts with fluidal outlines indicate that they were hot bombs and spatter incorporated into a pyroclastic density current during a large explosive eruption. The rock is interpreted as a subaqueous scoria-rich co-ignimbrite lag breccia, similar to subaerial phreatomagmatic scoria-rich deposits around Taal caldera lake in the Philippines. (Photo: M. J. Branney.)

(Figure 4.23) Map and true scale cross section (X Y) of Side Pike, to show thickness changes across formerly eastward-downthrowing volcanotectonic faults, which have since been re-activated in the opposite sense. Note the change in thickness of lacustrine sedimentary rocks (between G and H) and of ignimbrite (between I and J), and the steep fabrics at two of the faults that record hot deformation of ignimbrite. A peperitic sill cuts a fault at K indicating that the fault pre-dates dewatering of the sediments. Localities G to K are described in the text. (Mapping by M. J. Branney and E. W Johnson.)

(Figure 4.24) Generalized vertical section through part of the pyroclastic succession on the west side of Side Pike; see Figure 4.23 for the location and the text for explanation of units referred to as A to E After Branney (1988b and 1990b).

(Figure 4.25) Subaerial pyroclastic rocks at Side Pike, Langdale: (a) Cross-bedded phreatomagmatic fallout and surge deposits, which underlie the Side Pike ignimbrite. (b) Rhyodacitic welded ignimbrite (the Side Pike ignimbrite). (c) Accretionary lapilli-tuff in pyroclastic surge deposit that overlies the Side Pike ignimbrite. (Photos: M. J. Branney.)

(Figure 4.26) View of Long Crag from Coniston. The crags have been sculpted out of the ignimbrite of the Lincomb Tarns Formation and the low ground exposes Windermere Supergroup rocks, unconformably overlying the volcanic rocks. (Photo: D. Millward.)

(Figure 4.27) Map of the Coniston GCR site (based on BGS 1:50 000 Sheet 38, 1996).

(Figure 4.28) Details of peperitic andesite intrusions in the Seathwaite Fell Formation at Pets Quarry, Kirkstone Pass. (a) Andesite blocks have intruded lacustrine volcaniclastic sands and silts (pale coloured); patches of angular hydroclasts surround some block margins and sediment has been injected into cracks between the blocks. (b) Breccia formed by reworking of hot peperite on the lake floor. Geopetal sand partially infills vesicles later filled with carbonate (white) and chlorite (black) in the large andesite block. White carbonate beneath the block preserves a cavity that probably formed when the hot block heated water in the sediment matrix after its emplacement in a debris flow. The coin is 22 mm across. (Photos: M. J. Branney.)

(Figure 4.29) Map of the Stockdale Beck, Longsleddale GCR site (after Millward and Lawrence, 1985). Windermere Supergroup abbreviations: Ap, Kirkley Bank and Ashgill formations; Brw, Browgill Formation; Lsd, Longsleddale Member; SEn, Stile End Formation; SkB, Skelgill Formation.

(Figure 4.30) The Yarlside Volcanic Formation, approximately 450 m NW of Stockdale, showing flow-banded fel-site containing large nodules formed by intense silicification. (Photo: BGS no. L3143.)

(Figure 4.31) Map of the Threlkeld microgranite showing the location of Bramcrag Quarry

(Figure 4.32) Bramcrag Quarry: the Threlkeld microgranite is overlain by lavas and volcaniclastic sedimentary rocks of the basal part of the Borrowdale Volcanic Group. The contact slopes from top right to lower left. (Photo: BGS no. L2041.)

(Figure 4.33) Map of the Bowness Knott GCR site.

(Figure 4.34) Bowness Knott from the west with the low summit of Brown How to the left. (Photo: D. J. Fettes.)

(Figure 4.35) Map of the area around Beckfoot Quarry.

(Figure 4.36) Map of the Eskdale granodiorite around Waberthwaite Quarry.

(Figure 4.37) Photograph of Waberthwaite Quarry taken in 1935. (Photo: BGS no. A6707.)

(Figure 4.38) Map of the Carrock Fell Complex and the Skiddaw granite (after BGS 1:50 000 Sheet 23, 1997).

(Figure 4.39) Panoramic view of the eastern end of Carrock Fell from the east side of Mosedale. The Caldew valley and the village of Mosedale are located far left. The stream just left of centre (arrowed) is Further Gill Syke and the amphitheatre-like landslip scar to the right of this, beneath the summit, is the Scurth. (Photomosaic: BGS nos. A6751 and A6752)

(Figure 4.40) Map of the Carrock Fell GCR site.

(Figure 4.41) Modally layered gabbros from the Mosedale division. Alternation of leucocratic feldspathic and melanocratic mafic layers. (Photo: BGS no. A6743.)

(Figure 4.42) Map of the Haweswater intrusions, based on unpublished British Geological Survey maps by D. Millward and B. Beddoe-Stephens.

(Figure 4.43) Map of the Grainsgill GCR site (from transected by NNE-trending tungsten-bearing Geological Survey maps).

(Figure 4.44) Map of the Shap Fell Crags GCR site (after Soper and Kneller, 1990).

(Figure 4.45) Pink granite with xenoliths containing K-feldspar megacrysts. (Photo: D. Millward.)

(Figure 5.1) Map of central England showing locations of the occurrences of Caledonian igneous rocks and the GCR sites (after Pharaoh et al., 1993). GCR sites: 1, Croft Hill; 2, Buddon Hill (Mountsorrel); 3, Griff Hollow. Occurrences of plutonic rocks: Cl, Claxby; Co, Countesthorpe; KL, Kirby Lane; R, Rempstone; S, South Leicestershire diorites; Wa, Warboys 1. Occurrences of volcanic rocks: CW, Coxs Walk; EA, Eakring 146; Fo, Foston; GO, Great Osgrove Wood 1; Gst2, Gas Stamford 2; Ho, Hollowel; NC, North Creake 1; Sp, Sproxton; Up, Upwood 1; WD, Woo Dale 1.

(Figure 5.2) Map of the Croft Hill GCR site.

(Figure 5.3) View of Croft Hill, showing the NW face of Croft Quarry. To the left of the picture, the dark-grey parallel lineaments dipping from top left to bottom right represent a swarm of synplutonic intrusive sheets. (Photo: J. N. Carney.)

(Figure 5.4) Map of the Buddon Hill GCR site, based in part on BGS 1:10 560 scale mapping.

(Figure 5.5) Exposure of granodiorite at Buddon Hill showing two phases of aplite intrusion. (Photo: T. C. Pharaoh.)

(Figure 5.6) Map of the Griff Hollow GCR site (modified from Bridge et al., 1998). Positions of quarry faces in 1990 are shown.

(Figure 5.7) View of the western face of Griff No.4 Quarry. The base of the sill is at the foot of the lowest face, behind the stockpile in the centre of the photograph. The middle face, dark-grey in tone, exposes the poikilitic hornblende meladiorite layer and the upper face is in pale-grey hornblende diorite. The regular bedding above the latter represents the Coal Measures unconformably overlying the sill. (Photo: J. N. Carney.)

(Figure 6.1) Distribution of Ordovician and Silurian igneous rocks in Wales, and the location of GCR sites. 1, Rhobell Fawr; 2, Pen Caer; 3, Aber Mawr to Porth Lleuog; 4, Castell Coch to Trwyncastell; 5, St David's Head; 6, Cadair Idris; 7, Pared y Cefn-hir; 8, Carneddau and Llanelwedd; 9, Braich to du; 10, Llyn Dulyn; 11, Capel Curig; 12, Craig y Garn; 13, Moel Hebog to Moel yr Ogof; 14, Yr Arddu; 15, Snowdon massif; 16, Cwm Idwal; 17, Curig Hill; 18, Sarnau; 19, Ffestiniog granite quarry; 20, Pandy; 21, Trwyn-y-Gorlech to Yr Eifl quarries; 22, Penrhyn Bodeilas; 23, Moelypenmaen; 24, Llanbedrog; 25, Foel Gron; 26, Nanhoron quarry; 27, Mynydd Penarfynydd; 28, Skomer Island; 29, Deer Park.

(Figure 6.2) Generalized stratigraphical successions of the Lower Palaeozoic sequences of Wales, highlighting the major volcanic episodes. GCR sites are numbered and listed on Figure 6.1.

(Figure 6.3) Simplified geological successions of north Pembrokeshire, highlighting the Ordovician volcanic sequences. GCR site numbers are listed on Figure 6.1.

(Figure 6.4) Simplified geological successions of the Welsh Borderland, highlighting the Ordovician volcanic sequences. GCR site numbers are listed on Figure 6.1.

(Figure 6.5) Simplified geological successions of northern Snowdonia, highlighting the Ordovician volcanic sequences, in particular the Llewelyn Volcanic Group of the 1st Eruptive Cycle, and the Snowdon Volcanic Group of the 2nd Eruptive Cycle. GCR site numbers are listed on Figure 6.1. BP, Bedded Pyroclastic Formation; BTD, Braich to du Volcanic Formation; CCV, Capel Curig Volcanic Formation; CR, Conwy Rhyolite Formation; DV, Dolgarrog Volcanic Formation; FFV, Foel Fras Volcanic Complex; FGB, Foel Grach Basalt Formation; LCV, Lower Crafnant Volcanic Formation; LRT, Lower Rhyolitic Tuff Formation; MCV, Middle Crafnant Volcanic Formation; PT, Pitts Head Tuff Formation; TF, Tal y Fan Volcanic Formation; UCV, Upper Crafnant Volcanic Formation; URT, Upper Rhyolitic Tuff Formation.

(Figure 6.6) Simplified geological successions of Llŷn, highlighting the Ordovician volcanic sequences. GCR site numbers are listed on Figure 6.1.

(Figure 6.7) Map of the Rhobell Fawr GCR site, adapted from Kokelaar (1977).

(Figure 6.8) Porphyritic pargasite-bearing basalt of the Rhobell Volcanic Complex, Rhobell Fawr. (Photo: BGS no. L 1274.)

(Figure 6.9) Cognate cumulate block in basalt lava of the Rhobell Volcanic Complex, Rhobell Fawr. (Photo: R.E. Bevins.)

(Figure 6.10) Map of the Porth Maen Melyn area, Pen Caer GCR site (after Kokelaar et al., 1984a).

(Figure 6.11) Pillow lava from the Fishguard Volcanic Group, Strumble Head. The pillow in the centre of the photograph is 75 cm across (long axis). (Photo: R.E. Bevins.)

(Figure 6.12) Map of the north-eastern part of the Pen Caer GCR site (after Kokelaar et al., 1984a).

(Figure 6.13) Magma-wet sediment relationships at the base of a high-level basic intrusion, Pen Anglas. Magma has injected and loaded down into unlithified tuffaceous sediment, while the wet sediment has locally flamed up into the magma. Lens cap for scale. (Photo: R.E. Bevins.)

(Figure 6.14) Map of the Aber Mawr to Porth Lleuog GCR site, Ramsey Island (after Kokelaar et al., 1985).

(Figure 6.15) Ragged, elongate pumice fragments up to 12 cm in length in the Cader Rhwydog Tuff, Cader Rhwydog, Ramsey Island. (Photo: R.E. Bevins.)

(Figure 6.16) Wet sediment disturbance in thinly laminated turbiditic tuffs at the top of the Trwyn yr Allt Tuff, Cader Rhwydog Member, Cam Llundain, Ramsey Island. (Photo: R.E. Bevins.)

(Figure 6.17) Map of the south side of Abereiddi Bay (after Kokelaar et al., 1984a).

(Figure 6.18) Coarse lapilli-tuff of the Abereiddi Tuff Member, south side of Abereiddi Bay. (Photo: R.E. Bevins.)

(Figure 6.19) Map of the north side of Abereiddi Bay (adapted from Hughes et al., 1982).

(Figure 6.20) Map of the St David's Head Intrusion (after Bevins et al., 1994).

(Figure 6.21) Macrorhythmic layering between laminated quartz-gabbro (lighter bands) and laminated quartz-ferrogabbro (darker bands), looking to the NE across Porth Llong, St David's Head Intrusion. (Photo: R.A. Roach.)

(Figure 6.22) Granophyric gabbro from the St David's Head Intrusion, showing slight variations in felsic components, east of St David's Head. (Photo: R.A. Roach.)

(Figure 6.23) Map of the Cadair Idris area.

(Figure 6.24) Pillowed basalts from the Penygadair Volcanic Formation, SW of Penygadair summit. (Photo: D.G. Woodhall.)

(Figure 6.25) Map of the Pared y Cefn-hir area.

(Figure 6.26) View of the Pared y Cefn-hir area from the SW The prominent ridge is formed by the Cefn-hir Member and the rocky slopes to the right are in the Cregennen microgranite. (Photo: D.G. Woodhall.)

(Figure 6.27) Basic xenoliths in the margin of the Cregennen microgranite, south side of Pared y Cefn-hir [SH 6651 1506]. (Photo: D.G. Woodhall.)

(Figure 6.28) Map of the southern part of the Builth Inlier.

(Figure 6.29) Llanelwedd quarries, Builth Wells, viewed from the south. Westerly-dipping basic lavas, belonging to the Builth Volcanic Group, comprise much of the quarry area. Other volcanic units form the prominent features in the hills behind the quarry, the slack ground being eroded into softer shales. (Photo: R.E. Bevins.)

(Figure 6.30) Map of the Braich tu du area. Adapted from BGS 1:25 000 Sheet 65/66 (1985).

(Figure 6.31) The lower rhyolite (R) and ash-flow tuff (1) members of the Braich tu du Volcanic Formation separated by a thin sequence of marine siltstone, sandstone and basic tuffaceous sedimentary rocks (S) on the NE slopes of Nant Ffrancon [SH 648 621]. The columnar joints in the welded tuff (1) are perpendicular to its base, which dips steeply to the right. Reproduced from Howells et al. (1991).

(Figure 6.32) Map of Llyn Dulyn, after BGS 1:25 000 sheets 65/66 (1985) and 76 (1981).

(Figure 6.33) Moderately dipping welded ash-flow tuffs of the Capel Curig Volcanic Formation, SW side of Llyn Dulyn. (Photo: BGS no L1501.)

(Figure 6.34) Model of ash-flow emplacement, and of contact and internal facies relations of welded ash-flow tuffs with respect to environment of deposition (after Howells et al., 1991).

(Figure 6.35) (a) Interpretation of the depositional environments of the 1st and 2nd members of the Capel Curig Volcanic Formation, showing flow directions and the distribution of isolated pods of the 1st Member. (b), (c) Distribution of the 3rd and 4th members of the Capel Curig Volcanic Formation. After Howells and Leveridge (1980).

(Figure 6.36) Map and vertical section of the Capel Curig Volcanic Formation in the Capel Curig Anticline (after Francis and Howells, 1973).

(Figure 6.37) Map of the Llwyd Mawr Centre (after Roberts, 1969).

(Figure 6.38) Map of the Moel Hebog and Moel yr Ogof area (after BGS 1:10 000 Sheet SH54NE).

(Figure 6.39) Moel Hebog, viewed from the NE, showing primary and reworked tuffs of the Lower Rhyolitic Tuff Formation (LRT) overlying and enclosing disrupted rafts and blocks of the Pitts Head Tuff Formation (PT) near the southern margin of the Lower Rhyolitic Tuff Formation caldera. The Pitts Head Tuff Formation is underlain by sediments (S) and intruded by basalt (B). Reproduced from Howells et al. (1991).

(Figure 6.40) The lower outflow tuff of the Pitts Head Tuff Formation, Mod Hebog. The ash-flow tuff overlies coarse-grained sandstones (S) and bedded tuffs (Be). The base of the ash-flow tuff comprises non-welded tuff (T1) and is overlain by columnar jointed welded tuff (T2). A prominent zone of siliceous nodules (N) is overlain by densely welded tuff (T3) with a conspicuous, silicified, welding foliation [SH 5684 4694]. Reproduced from Howells et al. (1991). (Photo: BGS no. A14658.)

(Figure 6.41) View, generally northwards, from Moel Hebog, showing broad features of geology on Moel yr Ogof [SH 556 478]. Basaltic tuffs, hyaloclastites and volcaniclastic sediments (BP) and pillowed or massive basalts (B) of the Bedded Pyroclastic Formation are intruded by rhyolite (R). Reproduced from Howells et al. (1991). (Photo: BGS no. A14659.)

(Figure 6.42) Map showing the Yr Arddu Tuffs, subjacent sedimentary rocks and associated intrusions (after Howells et al., 1987).

(Figure 6.43) Siliceous nodules at the top of an acid ash-flow tuff, Lower Rhyolitic Tuff Formation, Yr Arddu. (Photo: BGS no. A14435.)

(Figure 6.44) Map of the Snowdon massif, modified after BUS 1:25 000 sheets 64/65 (1989) and 65/66 (1985).

(Figure 6.45) Lliwedd from Miner's Track showing the contact between the Lower Rhyolitic Tuff Formation and the Bedded Pyroclastic Formation near the centre of the ridge. (Photo: BGS no. A14391.)

(Figure 6.46) Details of the Bedded Pyroclastic Formation cropping out on the NE face of Yr Wyddfa, Snowdon above Llyn Glaslyn. (a) Photograph of NE face with geological boundaries added. (b) Key to the geological units exposed in a. (c) Sketch map of the Glaslyn Vent Complex. Reproduced from Howells et al. (1991).

(Figure 6.47) The ridge of Clogwyn y Person [SH 615 554] viewed from Cwm Glas. The ridge comprises well-jointed, acidic ash-flow tuff (1) at the base of the Upper Rhyolitic Tuff Formation. Below lie bedded basaltic sediments, basalt and hyaloclastite of the Bedded Pyroclastic Formation (BP), and above an intrusive rhyolite (R). Reproduced from Howells et al. (1991).

(Figure 6.48) The Idwal Syncline viewed along the axis, across Llyn Ogwen towards Cwm Idwal and the Devil's Kitchen. (Photo: BGS no. L2390)

(Figure 6.49) Map of the Cwm Idwal GCR site, after BGS 1:25 000 Sheet 65/66 (1985).

(Figure 6.50) The Idwal Slabs, on the eastern limb of the Idwal Syncline, composed of acidic ash-flow tuffs of the Lower Rhyolitic Tuff Formation. (Photo: BGS no. L2636.)

(Figure 6.51) Outcrop and measured sections of the Lower Rhyolitic Tuff Formation. Asterisks indicate distal outflow tuff sections. After Howells et al. (1991).

(Figure 6.52) (a) Map of the Capel Curig area (after BGS 1:10 000 Sheet SH75NE). Insets (b), (c) show sketch map and section of the basaltic vent at Curig Hill (after Howells et al., 1991).

(Figure 6.53) Base of bedded basalt agglomerate, Curig Hill 'vent' with acid tuff forming the lower feature near the wall. (Photo: BGS no. L1868.)

(Figure 6.54) Map of the Sarnau GCR site area, after BGS 1:10 560 sheets SH75SE (1977) and SH76NE (1979).

(Figure 6.55) Acid ash-flow tuff with blocks and clasts of mudstone, Middle Crafnant Volcanic Formation, Sarnau [SH 7721 5891]. (Photo: BGS no. L2905).

(Figure 6.56) Map of the Ffestiniog area showing the surface outcrop and limit of metamorphic aureole of the Tan y Grisiau Granite and the associated Bouguer gravity anomaly.

(Figure 6.57) The roof zone of the Tan y Grisiau granite intrusion, Ffestiniog Granite Quarry. (Photo: reproduced from Roberts, 1979.)

(Figure 6.58) Map of the Pandy area.

(Figure 6.59) Relationship between welded and unwelded ash-flow tuffs in the Pandy area.

(Figure 6.60) Map of the Garnfor Multiple Intrusion, north Llŷn (adapted from Tremlett, 1962).

(Figure 6.61) Map of the Penrhyn Bodeilas Intrusion, north Llŷn (adapted from Tremlett, 1962).

(Figure 6.62) Co-magmatic mafic enclaves in the Penrhyn Bodeilas Intrusion, Penrhyn Bodeilas. (Photo: R.E. Bevins.)

(Figure 6.63) Map of the Moelypenmaen area, north Llŷn.

(Figure 6.64) Map of the Llanbedrog area, south Llŷn.

(Figure 6.65) Map showing the distribution of the Nanhoron Suite of intrusions, south Llŷn.

(Figure 6.66) Map of the Mynydd Penarfynydd Layered Intrusion, south Llŷn.

(Figure 6.67) Picrite within the Mynydd Penarfynydd Layered Intrusion, north of Trwyn Talarfach [SH 2152 2580] Weathering of the cumulate texture has produced the distinctive honeycomb pattern. (Photo: W. Gibbons.)

(Figure 6.68) Banded melagabbros from the Mynydd Penarfynydd Layered Intrusion at Trwyn Talfarach [SH 2173 2580]. (Photo: W. Gibbons.)

(Figure 6.69) Map of Skomer Island (after Ziegler et al., 1969).

(Figure 6.70) Oblique aerial view of Skomer Island from the NW with Middleholm (Midland Island) and the Deer Park Penisula behind. Both islands are made up chiefly of basalts, hawaiites and mugearites of the Skomer Volcanic Group. (Photo: S. Howells.)

(Figure 6.71) Spherulites (up to 10 cm across) in The Basin Rhyolite, Skomer Volcanic Group, The Basin, Skomer Island. (Photo: R.E. Bevins.)

(Figure 6.72) Map of the Deer Park Peninsula (after Ziegler et al., 1969).

(Figure 7.1) Map of NW Scotland showing localities of alkaline intrusions, aligned roughly parallel to the Moine Thrust. Many alkaline dykes and sills occur in the Assynt district and also near Ullapool in the Achall Culmination (AC). GCR sites exemplifying nepheline-syenite dykes in the Foreland are indicated by NS. Caledonian calc-alkaline granites NW of the Great Glen are also shown. The Ratagain intrusion is largely calc-alkaline in character but has minor syenitic members (after Halliday et al., 1987, fig. 1).

(Figure 7.2) Map of the Assynt district showing the major thrusts, the two major alkaline intrusions, and the distribution of two of the six types of minor intrusive rocks. BA is the critical locality, at Bad na h-Achlaise, where nepheline-syenites and pyroxenites of the Loch Borralan intrusion are intruded into one of the klippen (the Cam Loch Klippe) of the Ben More Nappe. GCR sites in the thrust zone related to minor intrusive rocks are shown by circled numbers. 'Grorudite': 1, Glen Oykel South; 2, Creag na h-Innse Ruaidhe. 'Hornblende porphyrite': 3, Cnoc an Droighinn; 4, Luban Croma. 'Vogesite': 5, Allt nan Uamh; 6, Glen Oykel North (diatreme). 'Nordmarkite': 7, Allt na Cailliche. (After Sabine, 1953 and Johnson and Parsons, 1979, fig. 3.)

(Figure 7.3) 'Ledmorite' (melanite-augite nepheline-syenite) exposures at Ledmore in the Loch Borralan intrusion, looking west, with Cùl. Mòr (849 m) behind. Cùl. Mòr is in the Foreland and is composed of Torridonian and Cambrian sandstones. The Sole Thrust runs beyond the low hills in the middle distance. (Photo: I. Parsons.)

(Figure 7.4) Map of the Loch Borralan intrusion and its envelope rocks (modified after Johnson and Parsons, 1979).

(Figure 7.5) Map of the western part of the Loch Borralan intrusion. Units within the Cam Loch Klippe and on the western side of Loch Urigill are interpolated from exposures, as are the alkali feldspar-syenites of Cnoc na Sroine. The central part of the map shows actual exposures, boreholes and the extent of the pyroxenite bodies interpolated from them and from magnetic anomalies. The unornamented area in the central part of the map is a complex, largely unexposed assemblage of leucocratic nepheline-syenites, ledmorites and pyroxenites. Localities 1 to 3 are discussed in the text. (Compiled from Parsons and McKirdy, 1983, fig. 1; the Geological Survey special sheet for Assynt, 1923; Woolley, 1970, fig. 1; Notholt et al., 1985, fig. 3; Young et al., 1994, fig. 1.)

(Figure 7.6) Exposure map of the geology of the pseudoleucite-bearing 'borolanites' and associated rocks of the SE part of the Loch Borralan intrusion. (After Woolley, 1973, fig. 2.)

(Figure 7.7) Loch Ailsh and the upper valley of the River Oykel from the south. The snow-covered ridge is Ben More Assynt (998 m), with Conival (987 m) at the extreme left. The Loch Ailsh intrusion extends from just north of the loch to the base of the eastern end of this ridge. The dark, rocky hill in the left middle distance is Black Rock, formed of syenite S3 ('perthosite'). The rough ground immediately behind the cottage is Durness Group carbonate rocks, while the low cliff in the foreground is an exposure of Moine metasedimentary rocks. (Photo: I. Parsons.)

(Figure 7.8) Map of the Loch Ailsh intrusion. The extent of the pyroxenites in the Allt Cathair Bhàn is based largely on magnetic anomalies. (After Johnson and Parsons, 1979, fig. 15.)

(Figure 7.9) Loch Sail an Ruathair and the ridge of Sail an Ruathair in the northern part of the Loch Ailsh intrusion, from the east. The sketch shows the position of the upper contact of a dome of the early syenite, S1, overlain by the perthosite member, S3. (Photo: I. Parsons.)

(Figure 7.10) Sketch illustrating the relationships between a pyroxene syenite xenolith and feldspathic syenites in the Loch Ailsh intrusion, as seen in the River Oykel and Black Rock Burn areas. A typical xenolith would be about 1 m in length. (After Parsons, 1968, fig. 2.)

(Figure 7.11) Ben Loyal (764 m) from the north. The quartz-syenite peaks rise dramatically out of the surrounding moorland underlain by Moine metasedimentary rocks. (Photo: I. Parsons.)

(Figure 7.12) Map of the Loch Loyal syenite intrusions and their envelope rocks (compiled from Holdsworth and Strachan, in press; and Robertson and Parsons, 1974, fig. 1).

(Figure 7.13) Map of western Assynt showing distribution of nepheline-syenite ('ledmorite') dykes in the Foreland and their relationship to the Loch Borralan nepheline-syenites in the Moine thrust zone. GCR sites exemplifying the 'ledmorite' dykes and the Canisp Porphyry are also shown. The full extent of the Canisp Porphyry around Beinn Garbh is shown on Figure 7.15.

(Figure 7.14) Beinn Garbh (540 in, left) and Canisp (846 m, right) from Loch Assynt. The plateau of Beinn Garbh and the steps in the skyline of Canisp are formed of sills of Canisp Porphyry. (Photo: I. Parsons.)

(Figure 7.15) Distribution of sills and dykes of Canisp Porphyry in the Foreland. The dyke at the Laird's Pool, Lochinver, is farther to the west (see Figure 7.13). Only faults that affect Canisp Porphyry are shown. (After the Geological Survey special sheet for Assynt, 1923.)

(Figure 7.16) Distribution of sills and dykes between the Luban Croma and Allt nan Uamh sites, north of the Loch Borralan intrusion. (After Sabine, 1953, fig. 8.)

(Figure 7.17) Waterfall in Salterella Grit hardened by vogesite sill below, Allt nan Uamh (see Figure 7.16). (Photo: I. Parsons.)

(Figure 7.18) Facsimile of B.N. Peach's 'Ground Plan of possible Volcanic Vent, River Oykel, about three miles above Loch Ailsh' (from Peach et al., 1907).

(Figure 8.1) Late Caledonian granitic intrusions and plutonic suites of Scotland (starred numbers indicate those intrusions with GCR sites, named it italic type below): 1, Helmsdale; 2, Rogart (Loch Airighe Bheg); 3, Ratagain (Glen More); 4, Cluanie; 5, Abriachan; 6, Glen Garry; 7, Strontian (Loch Sunart); 8, Ross of Mull (Cnoc Mor to Rubh' Ardalanish and Knockvologan to Eilean a'Chlamain); 9, Kilmelford; 10, Etive (Bonawe to Cadderlie Burn and Cruachan Reservoir); 11, Glencoe fault intrusion (Stob Mhic Mhartuin and Loch Achtriochtan, Chapter 9); 12, Rannoch Moor; 13, Strath Ossian; 14, Ballachullish; 15, Duror of Appin (Ardsheal Hill and Peninsula and Kentallen); 16, Ben Nevis (Ben Nevis and Allt a'Mhuilinn, Chapter 9); 17, Corrieyairack; 18, Allt Crom; 19, Foyers; 20, Findhorn; 21, Monadhliath; 22, Boat of Garten; 23, Dorback; 24, Ben Rinnes; 25, Glen Livet; 26, Cairngorm; 27, Glen Tilt (Forest Lodge); 28, Lochnagar; 29, Craig Nardie; 30, Glen Gairn/Coilacreach; 31, Ballater; 32, Logie Coldstone; 33, Tomnaverie; 34, Cromar; 35, Torphins; 36, Balblair; 37, Bennachie; 38, Clinterty; 39, Peterhead; 40, Crathes/Gask; 41, Hill of Fare; 42, Mount Battock; 43, Glen Doll (Red Craig); 44, Glen Shee; 45, Comrie (Funtullich and Craig More); 46, Garabal Hill (Garabal Hill to Lochan Strath Dubh-uisge); 47, Arrochar; 48, Distinkhorn; 49, Spango; 50, Cairnsmore of Carsphairn; 51, Loch Doon (Loch Dee); 52, Broad Law; 53, Priestlaw; 54, Cockbums Law; 55, Cairngarroch Bay; 56, Portencorkrie; 57, Glenluce; 58, Mochrum Fell; 59, Fleet (Clatteringshaws Dam Quarry and Lea Larks); 60, Black Stockarton Moor; 61, Criffel (Lotus Quarries to Drungans Burn and Millour and Airdrie Hill); 62, Cheviot.

(Figure 8.2) Map of the eastern part of the Rogart pluton, including the Loch Airighe Bheg GCR site. The inset shows the whole Rogart complex.

(Figure 8.3) Poorly foliated outer quartz-monzodiorite of the Rogart pluton cut by veins of aplitic microgranite [NC 704 025]. (Photo: Susan Hall.)

(Figure 8.4) Xenoliths of appinitic rock in quartz-monzodiorite of the Rogart pluton [NC 703 026]. Dark biotite-rich selvages are visible at the margin of the xenolith above the compass. (Photo: Susan Hall.)

(Figure 8.5) Map of the Ratagain pluton, adapted from Hutton et al. (1993).

(Figure 8.6) Net-veined meladiorite ('appinite) from the Ratagain pluton. (Photo: W.E. Stephens.)

(Figure 8.7) Map showing the distribution of facies within the Strontian pluton, adapted from Sabine (1963).

(Figure 8.8) Map of the area around the Loch Sunart GCR site, Strontian pluton, adapted from BGS sheets 52E and 53.

(Figure 8.9) Mafic microgranular enclaves (MME) in porphyritic biotite granodiorite of the Strontian pluton, Rubh' an Torr-mholaich, Loch Sunart [NM 8133 6015]. (Photo: BGS no. C4000.)

(Figure 8.10) Map of the Ross of Mull pluton.

(Figure 8.11) Map of the area around the Cnoc Mor to Rubh' Ardalanish GCR site, Ross of Mull pluton, adapted from BGS 1:50 000 Sheet 43 and unpublished work, University of Liverpool.

(Figure 8.12) Irregular porphyritic microgranodiorite sheet cutting the marginal contaminated granite along the eastern margin of the Ross of Mull pluton. The slab-like xenoliths of the Moine country rock generally retain a pre-emplacement attitude in this marginal sheeted complex. Carraig Mhor [NM 3678 1762]. (Photo: A.J. Highton.)

(Figure 8.13) Map of the area around the Knockvologan to Eilean a' Chalmain GCR site, Ross of Mull pluton, adapted from BGS 1:50 000 Sheet 43 and unpublished work, University of Liverpool.

(Figure 8.14) Small meladiorite ('appinite) enclaves enclosed by a hornblende-biotite granodiorite hybrid host, centre of the Ross of Mull pluton, west of Port nan Ròn [NM 3124 1858]. (Photo: A.J. Highton.)

(Figure 8.15) Map of the Etive and Glencoe complexes, after Anderson (1937) and Batchelor (1987).

(Figure 8.16) Map of the area around the Bonawe to Cadderlie Burn GCR site, Etive pluton, adapted from BGS 1:50 000 Sheet 45W.

(Figure 8.17) Raft or roof pendant of hornfelsed Bonawe Succession (Dalradian) metasedimentary rocks (dark coloured) within the marginal variant of the Cruachan facies, Etive pluton. All are cross-cut by a c. 20 m-wide dyke of porphyritic microgranite (to the right of the photo). Quarry workings, Bonawe. (Photo: BGS no. MNS 4849.)

(Figure 8.18) Map of the area around the Cruachan Reservoir GCR site, Etive pluton, adapted from BGS 1:50 000 Sheet 45E.

(Figure 8.19) Aerial view of the Cruachan Reservoir GCR site, Etive pluton, looking WNW to Ben Cruachan. (Photo: BGS no. D 2571.)

(Figure 8.20) Map of the area around the Red Craig GCR site, Glen Doll pluton, with inset showing the location of the area with respect to the regional geology.

(Figure 8.21) Disaggregated xenoliths showing evidence of partial melting and assimilation into the host quartz-monzodiorite of the Glen Doll pluton at Red Craig [NO 294 757]. Leucocratic haloes are apparent around some xenoliths and schlieren. (Photo: BGS no. D 4550.)

(Figure 8.22) Map of the Forest Lodge GCR site, Glen Tilt igneous complex, based on unpublished British Geological Survey maps by D. Stephenson and B. Beddoe-Stephens. Note: Much of the area to the NW of the River Tilt is covered by head and scree deposits. Boundaries in this area are highly conjectural and the area shown as 'clioritic rocks' probably includes areas of granite and metasedimentary rocks.

(Figure 8.23) The waterfall at Dail-an-eas Bridge above Forest Lodge: view from the ruined bridge abutment. Siliceous metasedimentary rocks and a 2.5 m-thick bed of metalimestone (the latter surrounded by and tunnelled through by the waterfall) are cut by granitic veins of various types. The most prominent vein is also clearly visible in Hutton's 'lost drawing', reproduced in Figure 8.24. (Photo: D. Stephenson.)

(Figure 8.24) Plan of exposures in the River Tilt on the upstream side of Dail-an-eas Bridge, drawn by John Clerk of Eldin during Hutton's visit in 1785 and published as one of Hutton's 'lost drawings' by Craig et al. (1978). The outline is inaccurate and the detail is somewhat exaggerrated and stylized, but it illustrates well the features that Hutton observed; in particular the 'granite', 'limestone', 'schistus' and 'mixed rocks' are clearly labelled on the original. Note that the drawing is reproduced upside down to facilitate comparison with the photograph of Figure 8.23; the bridge abutments are indicated by the blank rectangles (bottom right and bottom left). Reproduced by permission of Sir John Clerk.

(Figure 8.25) General location map of the Comrie pluton. Taken from a paper by Pattison and Tracy (1991), who drew it from data in Tilley (1924).

(Figure 8.26) Map of the area around the Funtullich GCR site, Comrie pluton, adapted from MacGregor (1996).

(Figure 8.27) Map of the area around the Craig More GCR site, Comrie pluton, adapted from MacGregor (1996).

(Figure 8.28) Map of the Garabal Hill-Glen Fyne igneous complex (after Nockolds, 1941).

(Figure 8.29) Serpentinized peridotites (wehrlite) at I.ochan Strath Dubh-uisge, Garabal Hill-Glen Fyne igneous complex. (Photo: W.E. Stephens.)

(Figure 8.30) Map of the Loch Doon pluton, based largely on Gardiner and Reynolds (1932) with modifications from Ruddock (1969).

(Figure 8.31) Map of the Fleet pluton, adapted from Parslow (1968), showing the locations of the Clatteringshaws Dam Quarry and Lea Larks GCR sites.

(Figure 8.32) Map showing the principal petrological facies of the Criffel pluton.

(Figure 8.33) Contour map of SiO₂ variation in the Criffel pluton.

(Figure 8.34) (a) Typical clinopyroxene-biotite-hornblende granodiorite, with enclave from the margin of the Criffel pluton. (b) Biotite-muscovite granite from the interior of the Criffel pluton. (Photos: W.E. Stephens.)

(Figure 8.35) Photomicrograph of the biotite-muscovite granite from the Criffel pluton. (Photo: W.E. Stephens.)

(Figure 8.36) Map of the area around the Millour and Airdrie Hill GCR site, Criffel pluton, based on Phillips (1956), BGS 1:50 000 Sheet 5E (Dalbeattie) (1993) and observations by W.E. Stephens.

(Figure 8.37) (a) The distribution of appinitic intrusions and breccia pipes in the Duror of Appin cluster. Intrusions within the Ardsheal Hill and Peninsula GCR site are numbered for reference in the text. (b), (c), (d) and (e) Examples of outcrop patterns within the Duror of Appin cluster. The intrusion numbers correspond to those given in Figure 8.37a. Figures b, d and e are redrawn with minor modification from Bowes and Wright (1967).

(Figure 8.38) (a) Wall-parallel, steeply dipping layering of meladiorite and anorthosite at the SW margin of intrusion 14, in the Duror of Appin cluster (see Figure 8.37). (Photo: I.M. Platten.) (b) Composite dyke, Back Settlement, Ardsheal. The dyke, which cuts intrusion 12 to the NE, dips steeply towards the observer, with breccia in the footwall and lamprophyric microdiorite in the hanging wall. Magma has penetrated between breccia clasts at the irregular contact. (Photo: D. Stephenson.)

(Figure 8.39) Map of the Kentallen appinitic intrusion.

(Figure 8.40) Disharmonic minor folds at the margin of the Kentallen intrusion in the Sron Garbh section; view looking east. A 0.15 m-thick layer of quartzite on the left shows concentric folding (bottom) and fracture and pull-apart (top). A patch of breccia composed of 10 to 30 mm-long plates in a matrix of fine-grained micro-granite occupies the space between differently folded adjacent layers (centre). A set Dk1 dyke cuts the structures at the top of the photograph.

(Figure 8.41) Microdiorite dyke of set Dk1 cutting minor folds at the northern margin of the Kentallen intrusion; view looking east. The dyke shows axial concentration of mafic phenocrysts. The folded layer shows radial granitic veins forming a fan around the hinge (top). Traced downwards, this layer forms a box fold with few veins, but its core (centre) is mobilized and the bedding has been destroyed. The mobilized area forms a detachment surface isolating another fold closure (beside the scale), which shows an irregular mass of granite veins in the hinge and abrupt truncation of bedding on the upper limb. (Photos: I.M. Platten.)

(Figure 9.1) Location of late Silurian and Early- to Mid-Devonian age volcanic rocks of northern Britain. GCR sites: 1, South Kerrera; 2, Cruachan Reservoir (Chapter 8); 3, Ben Nevis and Allt a'Mhuilinn; 4, Bidean nam Bian; 5, Stob Dearg and Cam Ghleann; 6, Buachaille Etive Beag; 7, Stob Mhic Mhartuin; 8, Loch Achtriochtan; 9, Crawton Bay; 10, Scurdie Ness to Usan Harbour; 11, Black Rock to East Comb; 12, Balmerino to Wormit; 13, Sherriffmuir Road to Menstrie Burn; 14, Craig Rossie; 15, Tillicoultry; 16, Port Schuchan to Dunure Castle; 17, Culzean Harbour; 18, Turnberry Lighthouse to Port Murray; 19, Pettico Wick to St Abb's Harbour; 20, Shoulder O'Craig; 21, Eshaness Coast; 22, Ness of Clousta to The Brigs; 23, Point of Ayre; 24, Too of the Head.

(Figure 9.2) Stratigraphical relationships and ages of late-Silurian to Mid-Devonian age volcanic rocks of northern Britain. Biostratigraphical ages (where known) are given precedence and are plotted relative to the time-scale of Harland et al. (1990) (on the left). Note the consistent discrepencies between the biostratigraphical ages and the radiometric ages, which are not present if the time-scale of Gradstein and Ogg (1996) (on the right) is used. Where there is no biostratigraphical control (i.e. Southern Midland Valley, St Abb's and Cheviot), the volcanic sequences are projected from the radiometric dates. For example Cheviot at 396 Ma is early Emsian on the Gradstein and Ogg timescale, so it is plotted in the early Emsian position on the Harland et al. time scale. Ab, St Abb's; Ch, Cheviot; Cl, Clousta; Cr, Crawton; D, Deerness; DVF, Duneaton Volcanic Formation; Es, Eshaness, Papa Stour and Melby; Et, Ethie; FU, Ferryden and Usan; G, Glen Coe; F1, Hoy; Lo, Lorn; Lt, Lintrathen; MVF, Montrose Volcanic Formation; Oc, Ochil Hills; OVF, Ochil Volcanic Formation; P, Pentland Hills; S, Sidlaw Hills; T, Tinto.

(Figure 9.3) Ranges of whole-rock Sr, K/Th and La/Y from late Silurian and Devonian volcanic rocks of northern Britain, plotted against projected distance from the Iapetus Suture of Phillips et al. (1976). Adapted from Fitton et al. (1982, fig. 9). The heights of rectangles and bars represent the range of values within geographically related outcrops; the width of the rectangles represents each outcrop width. Southern Midland Valley: Pentland Hills and Lanarkshire, Ayrshire Coast, Straiton; Northern Midland Valley: Ochil Hills, north Fife hills, Sidlaw Hills, Montrose, Highland Border; Grampian Highlands: Ben Nevis, Glen Coe, Lorn Plateau; Orkney: Deerness, Hoy; Shetland: Eshaness, Papa Stour, Clousta; Note the anomalous values (dotted lines) from the Cheviot and St Abbs outcrops, close to the proposed line of suture, and from the Deerness outcrops of Orkney and all of the Shetland outcrops (see text for discussion).

(Figure 9.4) Map of Kerrera.

(Figure 9.5) Columnar jointing in andesite flow, south of Port Phadruig, Kerrera [NS 7888 2767]. (Photo: BGS no. C 2647.)

(Figure 9.6) Map showing units comprising the Ben Nevis igneous complex. Note the Inner Granite (essentially a ring intrusion) completely surrounding the down-faulted block. The contact between the two is where the rhyolite and 'flinty crush-rock' (i.e. an ancient vent) is found. The Outer Granite consists of four distinct (and mappable) subunits, emplaced in a margin-to-core sequence. Note also that the dyke-swarm cuts through all subunits of the Outer Granite that lie in its path, but does not penetrate the Inner Granite or the downfaulted block. After Bailey (1960), Burt (1994) and Burt and Brown (1997).

(Figure 9.7) View up the Allt a'Mhuilinn towards Coire Leis, showing the volcanic rocks of the downfaulted block (cliffs of Ben Nevis on the right), and the Inner Granite (low-lying ground on the left and the backwall of the coire in the distance. (Photomosaic: BGS nos. C 1794 and 1795.)

(Figure 9.8) (a) Map of Glen Coe showing rocks enclosed by the ring fracture (i.e. within the down-faulted block); Dalradian metasedimentary 'basement'; groups 1 to 7 (with groups 6 and 7 shown together); and undifferentiated intrusive rocks (rhyolite and andesite). Group 3 rocks are sandwiched between groups 2 and 4 rocks throughout most of the area, and only substantial group 3 outcrops are shown. The Etive Dyke-Swarm, minor intrusions, and small outcrops are omitted. The ring intrusion is not shown (see the Stob Mhic Mhartuin GCR site report). Note the incursion of the younger Cruachan granite into the cauldron block from the south. Redrawn after Clough et al. (1909), Roberts (1966a), Roberts (1974), and Moore (1995). (b) Map of the Glencoe cross-graben fault system preserved within the ring fracture (after Moore and Kokelaar, 1997). Figure 9.8(c) Block diagram showing the 3D structure of the Glencoe caldera as interpreted by Moore and Kokelaar (1997). The sections have been restored to a horizontal plane surface presumed to have been formed by the eruption of the 'Upper Glencoe Ignimbrite' (top of Group 2). Thin deposits from this eruption extended north of the North-eastern Graben Fault, but are not shown. The long axis of the block diagram lies along the axis of the Glencoe Graben. DAL, Dalradian metasedimentary rocks; BSC, Basal Sill Complex; LER, MER and UER, Lower, Middle and Upper Etive rhyolites (lower Group 2); LGI and UGI, Lower and Upper Glencoe ignimbrites (upper Group 2); p, phreatomagmatic tuff.

(Figure 9.9) View up Coire nam Beitheach towards Bidean nam Bian, Glen Coe, showing the outcrop of groups 1 to 4, plus the ring fracture and ring intrusion. See Figure 9.10 and the text for details. (Photo: BGS no. B619.)

(Figure 9.10) Interpretative sketch of Figure 9.9 showing the relationships between topography and lithologies at the Bidean nam Bian GCR site, after Clough et al. (1909). See text for details.

(Figure 9.11) The west face of Aonach Dubh, Glen Coe. Scree-covered lower slopes are Leven Schist, which is overlain by intrusive sheets (up to 17) and sedimentary rocks of the Basal Sill Complex (Group 1). The summit region is capped by the thicker rhyolites of Group 2. (Photo: BGS no. B616.)

(Figure 9.12) Peperite, clearly showing the brecciation of andesitic magma with fine-grained sandstones and shales forming the matrix between the andesite blocks. Beside the 'old road' near Achtriochtan farm, Glen Coe. This particular exposure is no longer visible; it was probably destroyed during construction of the new road, or has been covered by scree. (Photo: BGS no. C1154.)

(Figure 9.13) The NE face of Stob Dearg, Buachaille Etive Mor, Glen Coe. The lower, scree-covered slopes are of Dalradian metasedimentary 'basement'. The bulk of the mountain consists of rhyolite units (Group 2), with the summit area composed of a mass of intrusive rhyolite. The prominent slab in the lower left centre is the Waterslide slab' where fossil plant remains were collected. (Photo: D. Stephenson.)

(Figure 9.14) Buachaille Etive Beag, Glen Coe from the NE, looking towards Stob nan Cabar from Stob Mhic Mhartuin. (Photo: D.W. McGarvie.)

(Figure 9.15) The outward-dipping Glencoe ring fracture at Stob Mhic Mhartuin (down-faulted block on the right). The prominent dark band running up to the right is the 'flinty crush-rock', and above it (to its left) is the ring intrusion, here a porphyritic microdiorite, which is chilled at the contact. Between the 'flinty crush-rock' and the low ground on the right (Dalradian quartzites within the downfaulted block) are crushed and brecciated quartzites (see Figure 9.16). The outward-dipping orientation of the contact is probably due to rotation accompanying collapse of the downfaulted block. (Photo: BGS no. D1562.)

(Figure 9.16) Sketch (note variable scale) showing relationships in the Stob Mhic Mhartuin area between the downfaulted block, the ring intrusion, and the undisturbed metasedimentary rocks outside. Note the broad symmetry that is present, with 7 (ring intrusion) flanked by chilled margins (6 and 8), which are in turn flanked by 'flinty crush-rock' (5 and 9) — all of which probably constitute an ancient vent system. The 'flinty crush-rock' is flanked by a complex series of microbreccias to the west (2, 3 and 4), and by a much simpler microbreccia to the east (10), and these are themselves flanked by unbrecciated Dalradian metasedimentary rocks (1 — within the downfaulted block; and 11- outside the downfaulted block). After Roberts (1966b), and Garnham (1988). Key: 1, Bedded quartzites within downfaulted block; 2, Quartzites cut by veinlets of granulated quartzite; 3, Quartzite microbreccia; 4, Banded quartzite micro-breccia with matrix of 'flinty crush-rock'; 5, 'Flinty crush-rock' (note sharp and straight contact with 6); 6, Chilled margin of ring intrusion; 7, Ring intrusion; 8, Chilled margin of ring intrusion; 9, 'Flinty crush-rock' (note sharp but irregular contact with 8); 10, Quartzite microbreccia; 11, Undisturbed Dalrad-ian metasedimentary rocks outside the downfaulted block.

(Figure 9.17) Sketch showing the ring fracture and ring intrusion system around Glen Coe. Relationships are less clear in the south where there are difficulties distinguishing the ring intrusion from neighbouring intrusions. Minor outcrops of the ring intrusion (which are numerous) have been omitted for clarity. Redrawn after Clough et al. (1909), Roberts (1974) and Garnham (1988).

(Figure 9.18) View across Loch Achtriochtan, Glen Coe towards the Aonach Eagach ridge on the skyline. The ring fracture enters the left edge of the photograph about halfway up and runs towards the low point of the ridge at its extreme left. This subdued expression of the ring fracture is typical, and contrasts strongly with that shown in Figure 9.9. The distinctive cliffs running down to the right are Group 1 rocks (Basal Sill Complex), which overlie Leven Schist (Dalradian basement). (Photo: BGS no. B624.)

(Figure 9.19) Map of the Crawton Bay Volcanic Formation at Crawton Bay.

(Figure 9.20) Differential weathering in hexagonal columns of Crawton type basalt, Crawton Bay. (Photo: BGS no. D2454.)

(Figure 9.21) Map of coastal exposures of Montrose Volcanic Formation between Scurdie Ness and Usan Harbour, adapted from Jowett (1913).

(Figure 9.22) Bedded pebble and boulder conglomerate composed of lava clasts in coarsening up intercalation between lavas. Usan lavas, 500 m SE of Mains of Usan at [NO 732 554]. (Photo: R.A. Smith.)

(Figure 9.23) Map of coastal exposures of Montrose Volcanic Formation between Black Rock and East Comb, adapted from Jowett (1913).

(Figure 9.24) Base of lava with elongate amygdales above a lava breccia with a pale sandstone matrix. Ethie lavas, north of Kirk Loch at [NO 705 481]. (Photo: R.A. Smith.)

(Figure 9.25) Map and generalized vertical section of the Balmerino to Wormit GCR site.

(Figure 9.26) Lens of well-laminated sandstone between igneous sheets on the foreshore west of the Tay Bridge at Wormit. The lower sheet has a sharp but irregular, apparently intrusive, contact with the sandstone; the upper sheet shows evidence of magma-wet sediment interaction, with fragments of igneous material separated by irregular veins of pale sandstone and peperitic texture well seen on the right. (Photo: M.A.E. Browne.)

(Figure 9.27) Map and generalized vertical section of the Sheriffmuir Road to Menstrie Burn GCR site.

(Figure 9.28) The Ochil Fault scarp above Menstrie. The scarp face exposes a 600 m-thick sequence through the Ochil Volcanic Formation, dipping gently to the north (right). Menstrie Glen is in the bottom right and the prominent summit is Dumyat. (Photo: BGS no. D2066.)

(Figure 9.29) Map and generalized vertical section of the Craig Rossie GCR site.

(Figure 9.30) The east face of Craig Rossie; rhyodacite lava forms the summit and the lower crags are landslips. (Photo: BGS no. D2181.)

(Figure 9.31) Map of the Tillicoultry GCR site. The general succession is similar to that shown on Figure 9.27.

(Figure 9.32) Sketch-map showing radial disposition of dykes relative to diorite stocks in the Ochil Hills, after Francis et al. (1970).

(Figure 9.33) Castle Craigs Quarry, Tillicoultry. The quarry is along the line of the Ochil Fault plane; the back face exposes hornfelsed lavas and volcaniclastic conglomerates of the Ochil Volcanic Formation and the crags on the left are quartz-dolerite of the late-Carboniferous fault intrusion. (Photomosaic: M.A.E. Browne.)

(Figure 9.34) Map of the Ayrshire coast outcrops of Lower Old Red Sandstone volcanic rocks.

(Figure 9.35) Pillowed lobe of vesicular andesite in laminated sandstone at the base of the south-easterly of the Two Sisters stacks, Port Schuchan [NS 2468 1523]. (Photo: G. Durant.)

(Figure 9.36) Culzean Castle from an old engraving by W Daniell (c. 1838). Despite some vertical exaggeration, the spectacular setting of the castle on a cliff formed from a 35 m-thick sill of andesite is well conveyed.

(Figure 9.37) Pillowed base of an andesite sheet overlying volcaniclastic debris flow deposit at Culzean Harbour [NS 2311 1028]. (Photo: G. Durant.)

(Figure 9.38) Pillow structure in sparsely porphyritic pyroxene andesite south of John o'Groats Port [NS 2032 0780], Turnberry Lighthouse to Port Murray coast section. (Photo: G. Durant.)

(Figure 9.39) Inclusion of vesiculated sandstone in porphyritic andesite, Port Murray [NS 2058 0792].

(Figure 9.40) Sandstone infilling expanded cooling joints in andesite, Port Murray [NS 2087 0810]. (Photo: G. Durant.)

(Figure 9.41) Map of the St Abb's Head area, adapted from Greig (1988).

(Figure 9.42) St Abb's Head from the north. The volcanic rocks of the headland are separated from Silurian greywackes, forming the smoother topography beyond, by the St Abb's Head Fault; the glacial channel which follows the fault contains the Mire Loch, which is just visible. Note the pronounced scarp and dip slope topography of the volcanic rocks, which dip to the left and away from the camera. (Photo: by kind permission of The National Trust for Scotland.)

(Figure 9.43) Map of the Shoulder O'Craig volcanic vent, after Rock et al. (1986a).

(Figure 9.44) Sketch of the 'Loch Ness Monster' lamprophyre dyke, just north of the margin of the Shoulder O'Craig vent, after Rock et al. (1986a). (For location see Figure 9.43.)

(Figure 9.45) The cliffs of Eshaness, looking NE from the lighthouse. The nearest headland (the North Head of Caldersgeo) comprises andesitic pyroclastic breccias of unit 6 resting on andesites of unit 4. Most of the cliffs of the middle distance are andesites of unit 4; and the prominent dip-surface of the Grind of the Navir ignimbrite is just visible in the distance above the prominent stack (Moo Stack). (Photo: BGS no. D1660.)

(Figure 9.46) Location of Middle Old Red Sandstone volcanic rocks, major intrusions and major faults in western Shetland, after Mykura (1976).

(Figure 9.47) Map of the Eshaness coast, adapted from Geological Survey 1:10 560 sheets Shetland 19 and Shetland 23 (1959).

(Figure 9.48) Ignimbrite of the Grind of the Navir, Eshaness coast. The larger clasts are of alkali feldspar, commonly with a hollow core; smaller clasts are mainly collapsed pumice, glass shards and basic fragments. (Photo: BGS no. D1662.)

(Figure 9.49) (a) Map of the Ness of Clousta to The Brigs GCR site, adapted from Geological Survey 1:10 560 sheet Shetland 42 (1967) and Astin (1982). (b) The Muckle Billerin Tuff and Clousta Basalt: reconstructed cross section based on measured sections, showing the different thickness either side of the Voe of Clousta. Vertical exaggeration X2.5. (From Astin, 1982.)

(Figure 9.50) View of the Ness of Clousta to The Brigs GCR site, looking east from Muckle Head. The Muckle Head Tuff forms the rocks of the foreground; the Brigs Tuff forms the extreme right of the tidal island beyond; the upper part of the Clousta Conglomerate, dipping to the right (SSE), forms the prominent feature crossing the tidal inlet in the middle distance; and the right skyline is the ridge of Muckle Billerin, formed by the Clousta Basalt overlying the Muckle Billerin Tuff. (Photo: D. Stephenson.)

(Figure 9.51) Map of the Point of Ayre GCR site, Orkney.

(Figure 9.52) Map of the Too of the Head GCR site, Hoy, Orkney.

(Figure 9.53) The cliffs of Too of the Head on the west side of Rackwick Bay, Hoy. The pale rocks of the cliffs close to the buildings are composed of the Lower Eday Sandstone Formation. The lower and middle parts of the cliffs above and behind the buildings are composed of the basal volcaniclastic rocks and lava of the Hoy Volcanic Member. The paler rocks at the top of the cliff belong to the Lang Geo Sandstone Member of the Hoy Sandstone Formation. (Photo: BGS no. D1489.)

(Figure G1) The classification of fine-grained felsic and mafic crystalline igneous rocks. The distinction between basalt and andesite is based on the composition of the plagioclase feldspar present.

(Figure G2) The classification of coarse-grained felsic and mafic crystalline igneous rocks. The distinction between gabbroic rocks and diorite is based upon the composition of the plagioclase feldspar present. Medium-grained rocks are named by attaching the prefix 'micro' e.g. microgranite.

(Figure G3) The more-detailed classification of coarse-grained mafic crystalline igneous rocks, falling in the gabbroic rocks field of Figure G2. (a) Based upon the plagioclase, total pyroxene and olivine content, (b) based upon the plagioclase, orthopyroxene and clinopyroxene content, (c) figures (a) and (b) combine in three dimensions if necessary to form a tetrahedron.

(Figure G4) The classification of coarse-grained crystalline ultramafic rocks. Ultramafic rocks also include 'hornblendite' for rocks with more than 90% hornblende.

(Figure G5) The classification of lamprophyres encountered in this volume.

(Figure G6) The chemical classification of fine-grained crystalline igneous rocks, used when it is not possible to classify rocks according to their mineralogy due to very fine grain size. Heavily altered rocks such as are commonly encountered in the Caledonian Province can be difficult to classify chemically owing to the loss or addition of highly mobile elements such as sodium (Na) and potassium (K) and accompanying changes in silica (SiO₂).

Tables

Table 1.1a Ordovician Igneous Rocks Block: networks and GCR site selection criteria Volcanic Rocks and Ophiolites of Scotland Network, Chapter 2.

Table 1.1b Silurian and Devonian Plutonic Rocks Block: networks and GCR site selection criteria. Alkaline Intrusions of the NW Highlands of Scotland Network, Chapter 7.

Table 1.1c Silurian and Devonian Volcanic Rocks Block: networks and GCR site selection criteria. Scotland Network, Chapter 9

(Table 6.1) Stratigraphy of the Cadair Idris area, showing correlations with earlier nomenclature.

(Table 6.2) Stratigraphy of the Pared y Cefn-hir area, showing correlations with earlier nomenclature.

(Table 6.3) Stratigraphy and lithologies of volcanic rocks of the Builth Inlier.

(Table 7.1) Inter-relationship of alkaline igneous activity and major tectonic events in the Moine thrust zone (after Halliday et al., 1987). Events in italic were essentially synchronous. MTP: Moine thrust plane. BMTP: Ben More thrust plane. STP: Sole thrust plane. The radiometric ages are from the following sources: 1. Johnson et al., 1985. 2. Halliday et al., 1979a. 3. Van Breemen et al., 1979a. 4. Van Breeman et al., 1979b. 5. Halliday et al., 1987.

(Table 7.2) Glossary of uncommon or varietal rock names employed for members of the alkaline suite in the NW Highlands.

(Table 9.1) Nomenclature of the Outer and Inner granites of Ben Nevis by various workers. Si0₂ contents from Burt (1994).

(Table 9.2) Succession in the down faulted block of Ben Nevis (after Burt, 1994).

(Table 9.3) Stratigraphy of the volcanic and associated sedimentary rocks preserved in the Glencoe cauldron subsidence.

(Table 9.4) Sequence of sedimentary rocks sandwiched between the Dalradian metasedimentary rocks and overlying volcanic rocks (from Bailey, 1960). Bed thicknesses are approximate.

(Table 9.5) Metasedimentary rocks found in the Glen Coe area.

References