Figure captions

(Figure 1.1) General bedrock geology of the Grampian Highlands and Inner Hebrides south-east of the Great Glen Fault, showing the outcrops of Dalradian groups and major faults. Adapted from Stephenson and Gould (1995) and the BGS 1:625 000 scale Bedrock Geology map (UK North, 2007).

BBF Bridge of Balgie Fault, ELF Ericht–Laidon Fault, GDF Glen Doll Fault, GF Garabal Fault, GLF Gleann Liath Fault, LTF Loch Tay Fault, MF Markie Fault, PBF Pass of Brander Fault, RF Rothes Fault, SF Sronlairig Fault, TF Tyndrum Fault.

(Figure 1.2) Terrane map of the northern British Isles showing the outcrop of the Dalradian Supergroup in the Grampian Terrane of Scotland and Ireland and in Shetland. Adapted from the BGS 1:500 000 scale Tectonic map of Britain, Ireland and adjacent areas (1996) and the BGS 1:625 000 scale Bedrock Geology map (UK North, 2007).

(Figure 1.3) Distribution of ancient continental fragments and Caledonian orogenic belts around Britain and Ireland prior to the opening of the North Atlantic Ocean in Palaeogene time (after Holdsworth et al., 2000).

(Figure 1.4) Edward Battersby Bailey in a typical field pose. Note the mode of dress: shabby jacket with various pieces of equipment tied on with string; shorts, worn in all weather and all seasons; lack of socks (they would only get wet); shoes (not boots), with holes in the toes (legend has it that he would deliberately cut the toes out of new shoes in order that the water could run out). Other legends tell that first thing every morning he would stand in a stream so that he didn’t worry about getting his feet wet for the rest of the day and then eat his packed lunch so that he didn’t have to carry it and waste time eating it later. After mapping and interpreting huge areas of the Grampian Highlands for the Geological Survey and then as Professor of Geology at Glasgow University, he became Director of the Geological Survey (1937–1945) and was knighted in 1945. (Photo: BGS No. P 225785, reproduced with the permission of the Director, British Geological Survey, © NERC.)

(Figure 1.5) Divisions of the Grampian Highlands as used in this volume and locations of GCR sites, numbered as in Table 1.1.

(Figure 1.6) Overall Dalradian stratigraphy with interpreted depositional environments, water depth and subsidence history, based mainly on successions in the western and south-western parts of the Grampian Highlands and Inner Hebrides. Representative formations are from the Corrieyairack, Laggan and Glen Spean areas (Grampian Group), the Lochaber area (Appin Group) and Islay, Jura and Kintyre (Argyll and Southern Highland groups). After Anderton (1985) and Strachan and Holdsworth (2000).

(Figure 1.7) Block diagram of major structures in the Grampian Highlands. Brittle faults, major mafic and ultramafic intrusions and minor intrusions are not shown. Sections A, B, C and D were adapted from an original by P.R. Thomas (1979) and incorporated in an overall model in Stephenson and Gould (1995).

AS Appin Syncline, BA Bohespic Antiform, BAS Ballachulish Slide, BCH Beinn a'Chuallich folds, BDS Beinn Don Syncline, BES Benderloch Slide, BLA Beinn na Lap Antiform, BLS Ben Lawers Synform, BOS Boundary Slide, CIA Creag na h'Iolaire Anticline, CS Corrieyairack Syncline, DD Drumochter Dome, ES Errochty Synform, FWS Fort William Slide, GCA Glen Creran Anticline, GMS Glen Mark Slide, GS Grampian Slide, HBD Highland Border Downbend, HBS Highland Border Steep Belt, KA Kinlochleven Anticline, OSB Geal-charn–Ossian Steep Belt, SBS Stob Ban Synform, SMS Sron Mhor Synform, TMA Tom Meadhoin Anticline, TSB Tummel Steep Belt.

(Figure 1.8) Contrasting interpretations of the structure of the classic section along Loch Leven by different authors (after Stephenson and Gould, 1995).

(a) Bailey (1934)

(b) Roberts and Treagus (1977b, 1977c): revised stratigraphical correlations and drastically revised projections at depth

(c) Hickman (1978): primary folds are identified only in the eastern part of the section

AS Appin Syncline, BAS Ballachulish Slide, BS Ballachulish Syncline, BWS Blackwater Synform, FWS Fort William Slide, KA Kinlochleven Anticline, KAF Kinlochleven Antiform, MA Mamore Anticline/Antiform, MS Mamore Syncline, SBS Stob Ban Synform, TMA Tom Meadhoin Anticline, TS Treig Syncline.

(Figure 1.9) Cross-section to illustrate the structure in the Glen Roy and Glen Spean area; a north-eastern continuation of the structures shown in (Figure 1.8) (after Key et al., 1997).

(Figure 1.10) Alternative models for the structural development of the Grampian Highlands (after Stephenson and Gould, 1995). Individual stages are not numbered (D1, D2 etc.) to avoid confusing and unintentional time correlations between the models but all show deformation up to and including the post-nappe D4 phase.

(a) Root-zone and 'mushroom' models: final stage adapted from Thomas (1980)

(b) Nappe fans/'fountains': adapted from Roberts and Treagus (1977a, 1977c) and Treagus (1987)

(c) Gravity sliding of rootless nappes: adapted from Shackleton (1979)

(d) North-westward movement and backfolding: from model of Hall in Fettes et al. (1986)

Stipple Grampian Group, BAS Ballachulish Slide, BLF Ben Lui Fold-complex, BOS Boundary Slide, FWS Fort William Slide, OSB Geal-charn–Ossian Steep Belt, SBS Stob Ban Synform, TN Tay Nappe.

(Figure 1.11) Model for the evolution of the Tay Nappe (after Krabbendam et al., 1997).

(a) Lower levels of upright F1 folds are subjected to top-to-the-south-east D2 shearing. The position of the older part of the Highland Border Complex is highly speculative.

(b) F3 folding steepens structures in the north-west; the F4 Highland Border Downbend results in the Highland Border Steep Belt to the south-east, which consequently includes outcrops of downward-facing F1 folds and the limit of D2 deformation.

HBD Highland Border Downbend.

(Figure 1.12) Distribution of metamorphic facies within the Grampian Highlands, as adapted from Fettes et al. (1985) by Stephenson and Gould (1995) and Strachan et al. (2002).

B Balquidder, C Cairngorms, D Deeside, ESZ Eilrig Shear-zone, M Monadhliath, S Schiehallion, TSB Tummel Steep Belt.

(Figure 1.13) Reconstruction showing the positions of Baltica, Amazonia and Laurentia, prior to the break-up of the supercontinent of Rodinia and formation of the Iapetus ocean in late Neoproterozoic time (after Soper, 1994b). Arrows indicate the relative movements of the continental blocks during subsequent rifting.

A–C western margin of Appalachian–Caledonian orogenic belt, G Greenland, N Newfoundland, S Scotland.

(Figure 1.14) Global palaeogeographical reconstructions from the mid Neoproterozoic to the mid Silurian. Modified after Torsvik et al. (1996) and Holdsworth et al. (2000).

(a) The supercontinent Rodinia at c. 750 Ma. The Grenvillian orogenic belts that welded the Rodinia continent together are indicated in black. Rifting has commenced between Laurentia and East-Gondwana.

(b) Late Neoproterozoic, c. 600–580 Ma. Rifting between the continents of Laurentia, Baltica and the Amazonia sector of West Gondwana. See (Figure 1.13) for the situation immediately prior to this.

(c) Late Neoproterozoic–Cambrian, c. 550–540 Ma. The Iapetus Ocean is at its widest. Clastic and carbonate deposition occurs along the southern margin of Laurentia.

(d) Mid Ordovician, c. 470 Ma. Iapetus is in the process of closing. Collision of oceanic and microcontinental arcs with Laurentia, e.g. the Midland Valley Terrane, results in the Grampian Event in Scotland and the Taconic Event in North America.

(e) Early Silurian, c. 440 Ma, Continental terranes that have spalled off Gondwana, notably Avalonia, collide with Laurentia as the Iapetus Ocean closes and the Rheic Ocean widens. The start of the Scandian Event.

(f) Mid Silurian, c. 425 Ma. Final closure of Iapetus and Tornquist oceans. Collision of Baltica with the Greenland sector of Laurentia gives rise to the main Scandian Event (435–425 Ma).

MVT Midland Valley Terrane, SP South Pole.

(Figure 1.15) Schematic cross-sections to show the progressive development of the rifted Laurentian margin in Scotland during a) late Appin Group time b) Crinan Subgroup time and c) Southern Highland Group time (after Anderton, 1985). Basaltic volcanic rocks and intrusions are shown in black (in c only).

(Figure 1.16) A possible tectonic model for the Grampian Event in Scotland, which is here attributed to the collision of an intra-oceanic subduction zone and island arc (now possibly forming the basement to the Midland Valley Terrane) with the margin of Laurentia during closure of the Iapetus Ocean (Strachan, 2000 after Dewey and Ryan, 1990 with modifications to text to reflect more-recent evidence for the timing of events).

(Figure 1.17) Reconstruction of the final stages of the Caledonian Orogeny with multiple plate collisions and re-alignments in mid Silurian to Early Devonian time (after Soper et al., 1992).

(a) Wenlock–Ludlow, c. 420 Ma. The Iapetus Ocean has almost closed as Eastern Avalonia converges with Baltica.

(b) Lochkovian, c. 400 Ma. The Rheic Ocean has closed as Armorica collides with Eastern Avalonia and strike-slip re-alignment of terranes occurs between Laurentia and Baltica (the Acadian Event). Farther south, Iberia is converging with Armorica prior to collision in Mid Devonian time.

GGF Great Glen Fault, HBF Highland Boundary Fault, MTB Moine Thrust Belt.

(Figure 2.1) Map of the South-west Grampian Highlands showing subgroups of the Dalradian Supergroup, the axial plane traces of major folds, the line of section A–B on (Figure 2.3) and the locations of the GCR sites included in this chapter. Only areas described in Chapter 2 are ornamented.

GCR sites: 1 Garvellach Isles, 2 Caol Isla, Islay, 3 Rubha a’Mhail, Islay, 4 Kilnaughton Bay, Islay, 5 Lussa Bay, Jura, 6 Kinuachdrach, Jura, 7 Surnaig Farm, Islay, 8 Ardbeg, Islay, 9 Ardilistry Bay, Islay, 10 Black Mill Bay, Luing, 11 Craignish Point, 12 Fearnach Bay, 13 Kilmory Bay, 14 Port Cill Maluaig, 15 Strone Point, 16 Kilchrenan burn and shore, 17 West Tayvallich peninsula, 18 South Bay, Barmore Island, 19 Loch Avich, 20 Bun-an-Uillt, Islay, 21 Kilchiaran to Ardnave Point, Islay.

Abbreviations: AA Ardrishaig Anticline, BF Bolsa Fault, IA Islay Anticline, KBS Kilmory Bay Syncline, KSZ Kilchiaran Shear-zone, LAS Loch Awe Syncline, LGF Loch Gruinart Fault, LST Loch Skerrols Thrust, PBF Pass of Brander Fault, TF Tyndrum Fault, TS Tayvallich Syncline.

(Figure 2.2) Stratigraphical columns (not to scale) showing lateral correlations between members and formations of the Dalradian Supergroup in the South-west Grampian Highlands. A the islands of Islay, Jura and the Garvellachs, B the Loch Awe Syncline, C the Ardrishaig Anticline, core and south-east limb, D and E rocks of uncertain affinity on Islay and Colonsay, and those forming the basement to the Dalradian Supergroup.

GB Great Breccia, DB Disrupted Beds.

(Figure 2.3) True-scale cross-section showing the location of GCR sites included in this chapter (numbered as on (Figure 2.1)), the correlation between stratigraphical sequences, and major structures, across the South-west Grampian Highlands. Line of section A–B is shown on (Figure 2.1). (Cross-section: P.W.G. Tanner.)

(Figure 2.4) Facsimile copy of part of the geological map of Islay published by E.B. Bailey (1917).

(Figure 2.5) Map of the Garvellach Isles, Firth of Lorn, after Spencer, (1971).

(Figure 2.6) Tillite bed containing large exotic clasts of pink granite, from the north end of Garbh Eileach, Garvellach Isles. Hammer shaft is 47 cm long. (Photo: P.W.G. Tanner.)

(Figure 2.7) Map of the shore section north of Caol Isla distillery, Isle of Islay. Adapted from Fairchild, (1991).

(Figure 2.8)

(a) Casts of sand-filled dewatering cracks seen in relief on the base of a metasandstone bed from Leac Thiolastaraidh, north of Caol Isla, Isle of Islay [NR 4297 7037].

(b) Negative print taken from an acetate peel of a typical dewatering crack from Leac Thiolastaraidh. The illustration shows a sandstone bed (s) overlying a layer of mudrock (m), both units having been cut by the upward injection of a sand-filled dewatering crack. Following exposure to erosion at the Earth’s surface, the mudrock layer lying beneath the sandstone might be eroded away, leaving the sandstone infill (c) as a cast protruding from the base of the bed, as in (Figure 2.8)a.

(Photos: P.W.G. Tanner.)

(Figure 2.9) Map of the coastal section at the Rubha a’Mhail, Isle of Islay, after Fairchild, (1991). The outline map (a) shows the locations of detailed sections (b) and (c).

(Figure 2.10) Stromatolite bodies from Member 3 of the Bonahaven Dolomite Formation, north-east of Port a’Chotain, Rubha a’Mhail GCR site, Isle of Islay.

(a) Domal stromatolite bioherms at Bagh an da Dhorius, [NR 410 788]. Hammer shaft (arrowed) is 47cm long.

(b) Large bioherm at [NR 407 789]. Hammer shaft is 47 cm long.

(Photos: P.W.G. Tanner.)

(Figure 2.11) Map of the area around the Kilnaughton Bay, Islay GCR site, south-east Islay.

(Figure 2.12) Stratigraphical log of the pebble beds in the upper part of the Scarba Conglomerate Formation from [NR 3479 4440–3492 4464, on the north side of Carraig Fhada, Kilnaughton Bay, Isle of Islay.

(Figure 2.13) Rosettes and blades of kyanite, largely pseudomorphed by kaolinite and pyrophyllite (Burgess et al., 1981), lying on a bedding plane at a low angle to the S1 cleavage in the Jura Quartzite at Kilnaughton Bay, Isle of Islay. Scale is in cm/mm. (Photo: P.W.G. Tanner.)

(Figure 2.14) Map of the area around the Lussa Bay GCR site, Isle of Jura.

(Figure 2.15) A representative, 55 cm-thick, pebbly unit from the Scarba Conglomerate Formation at Lussa Bay, Isle of Jura, showing poorly developed graded bedding with rip-up clasts of metamudstone. Beds young to the right of the photo (south-east). Spirit level (top left) is 5 cm long. (Photo: P.W.G. Tanner.)

(Figure 2.16) Map of the area around the Kinuachdrachd GCR site, Isle of Jura (after BGS 1:50 000 Sheet 36, Kilmartin, 2003 and Anderton, 1977).

(Figure 2.17) Refracted S1 cleavage cutting near-horizontal bedding close to the hinge-zone of a mesoscopic F1 fold, in metasandstone beds, viewed to the north-east, Kinuachdrachd, Isle of Jura. Spirit level is 5 cm long. (Photo: P.W.G. Tanner.)

(Figure 2.18) Map of the area around the Surnaig Farm GCR site, south-east Islay, showing the ‘sandstone dykes’ locality.

(Figure 2.19) A folded sedimentary dyke (viewed to the west), within the Laphroaig Quartzite Formation, 300 m south-west of Surnaig Farm, south-east Islay [NR 3982 4525]. The dyke is between 40 cm and 50 cm wide and the spirit level (centre) is 5 cm long. (Photo: P.W.G. Tanner.)

(Figure 2.20) Map of the area around the Ardbeg GCR site, south-east Islay, showing the stilpnomelane locality.

(Figure 2.21) Photomicrograph (in plane-polarized light) of the stilpnomelane-bearing metamafic sill on the foreshore 400 m east of Ardbeg Distillery at [NR 4185 4625]. Radiating clusters of stilpnomelane can be seen overgrowing actinolite, albite, quartz, and epidote. The field of view is 6 mm. (Photo: A. Condron.)

(Figure 2.22) Map of the area around the Ardilistry Bay GCR site, south-east Islay.

(Figure 2.23) Topographic expression of sills of metamafic rock at Ardilistry Bay, south-east Islay, viewed looking south-east from Locality X on (Figure 2.22). (Photo: P.W.G. Tanner.)

(Figure 2.24) Schematic vertical section through the metapyroxenite-bearing sill at Ardilistry Bay, south-east Islay.

(Figure 2.25) Map of the area around the Black Mill Bay GCR site. A–D, localities mentioned in the text. Inset: An equal-area stereographic projection of poles to bedding, slaty cleavage (S1), and crenulation cleavage (S2), together with the best-fit line (π-girdle) containing the poles to bedding and cleavage. The nearly horizontal π-axis, gives the mean orientation of the related major fold axis.

(Figure 2.26) A gravity-flow deposit, or debrite, at locality A on (Figure 2.25) [NM 7311 0875], Black Mill Bay GCR site. The scale is 5 cm long.

(a) A near-vertical face approximately parallel to S1, showing deformed clasts of sandstone in a silty matrix.

(b) A horizontal, plan-view section through the deformed clasts shown in (a).

(c) An illustration of lithological control on cleavage development at locality A. The near-vertical S1 cleavage dominates in metacarbonate rock (M) and in the debrite (D), whereas the S2 crenulation cleavage is more strongly developed in the intervening black pelite (P) and gives rise to a near-horizontal parting in this lithology. A sedimentary dyke (S), now folded and cleaved, cuts the debrite and the pelite.

(Photos: P.W.G. Tanner.)

(Figure 2.27) Map showing the outline geology of the Craignish Point GCR site.

(Figure 2.28)

(a) Weathered-out cavities in metasandstone, previously occupied by calcite pseudomorphs of bow-tie gypsum, Craignish Phyllite Formation, Craignish Point. The bow-ties are 3–6 mm across.

(b) Pseudomorphs of butterfly-twinned gypsum lying on a bedding plane in the Craignish Phyllite Formation, Craignish Point. The pseudomorphs are up to 5 cm across.

(Photos: P.W.G. Tanner.)

(Figure 2.29) Map of the area around the Fearnach Bay GCR site, Loch Melfort. A, locality mentioned in the text.

Inset: Equal-area stereographic projections of poles to bedding, together with minor D1 fold hinges, and slaty cleavage (S1) (see text for explanation).

(Figure 2.30)

(a) Cross-lamination at the base of a massive bed of metacarbonate rock in the Craignish Phyllite Formation, [NM 8336 1406], Fearnach Bay, Loch Melfort. Scale is 5 cm long.

(b) The contact between a basic sill (B) and phyllitic semipelite (P) folded by an upright F1 syncline at locality A [NM 8350 1342], Fearnach Bay, Loch Melfort (Figure 2.29). The fanned cleavage in the phyllite contrasts with the axial planar cleavage in the metadolerite sill (M). A thin band of quartzite (Q) occurs at the contact. Hammer shaft is 60 cm long.

(c) Intense folding of sandy metacarbonate layers, and cleavage refraction in the intervening metapelite, within the Craignish Phyllite Formation, a short distance north of locality A [NM 8350 1342], Fearnach Bay, Loch Melfort (Figure 2.29). The bar scale is 5cm long.

(Photos: P.W.G. Tanner.)

(Figure 2.31) Preliminary map of the area around the Kilmory Bay GCR site with geological boundaries taken from Roberts (1977c).

(Figure 2.32) Panoramic view of a train of F1 folds with fanned spaced cleavages, plunging north-north-east, Crinan Grit Formation (Ardnoe Member), Kilmory Bay [NR 700 743]. (Photo: P.W.G. Tanner.)

(Figure 2.33) En-echelon segmented sedimentary dyke (centre) parallel to spaced axial planar cleavage, Ardrishaig Phyllite, Kilmory Bay [NR 697 728]. (Photo: P.W.G. Tanner.)

(Figure 2.34) Map of Knapdale and north Kintyre (based on Roberts, 1977c), showing outcrops of the main Dalradian units and locations of GCR sites: 1 West Tayvallich Peninsula, 2 Kilmory Bay, 3 Port Cill Maluaig, 4 South Bay, Barmore Island. AA Ardrishaig Anticline, KBS Kilmory Bay Syncline, TS Tayvallich Syncline. Inset shows the geology of the Port Cill MaluaigGCR site (3).

(Figure 2.35)

(a) Minor F2 folds showing strongly curved fold-hinges, which plunge in opposing directions, Port Cill Maluaig. Hammer shaft is 47 cm long.

(b) Mesoscopic and minor F2 folds from Port Mhoirich (Port Cill Maluaig GCR site), viewed to the north-east. Note the control of bed thickness on the wavelength of the folds. Hammer shaft is 47 cm long.

(Photos: P.W.G. Tanner.)

(Figure 2.36) Map of the area around the Strone Point GCR site, showing the position of the Ardrishaig and Strone Point anticlines, linked by an inferred syncline (modified from Borradaile, 1970). The inset map shows the detailed geology of the Strone Point GCR site.

(Figure 2.37) Strongly folded and cleaved layers of orange-brown metacarbonate rock (C) and grey-green phyllitic metamudstones (P) define rather open S-folds on the lower part of the hinge-zone of the Strone Point Anticline at Strone Point [NN 1183 0884]. The penetrative S1 cleavage dips at a shallow angle to the north-west, the direction of view being to the south-west. Solid lines highlight the trace of the bedding. Hammer shaft is 47 cm long. (Photo: P.W.G. Tanner.)

(Figure 2.38) Sketch of typical curvilinear folds at Strone Point, based on part of figure 19 of Voll (1960). The geometry of the folds is illustrated by the equal-area stereographic projection, reproduced from figure 2a of Borradaile (1970), augmented by data collected by P.W.G. Tanner.

(Figure 2.39) Map of the hinge-zone of the F1 Loch Awe Syncline at Kilchrenan, showing the principal exposures of the Kilchrenan Conglomerate Member of the Tayvallich Slate and Limestone Formation (after Borradaile 1973, 1977).

(Figure 2.40) The Kilchrenan Conglomerate in exposures on the bank of the Kilchrenan Burn. The clasts are of quartzite in a gritty, muddy matrix. Coin is 2 cm diameter. (Photo: J.E. Treagus.)

(Figure 2.41) Simplified map of the West Tayvallich peninsula. Numbers refer to sections described in the text. Modified after BGS 1:50 000 Sheet 28E (Knapdale, 1996). Additional information from Elles (1935), Wilson and Leake (1972) and Gower (1977).

(Figure 2.42) Basaltic pillow lavas in the Tayvallich Volcanic Formation showing concentric bands of vesicles, coast of An Aird [NR 7020 8370]. Hammer shaft is 37 cm long. (Photo: BGS No. P 219459, reproduced with the permission of the Director, British Geological Survey, © NERC.)

(Figure 2.43) Map of the coastal section between Barmore Island, Loch Fyne and East Loch Tarbert; outcrops of basic meta-igneous rock omitted (after Roberts, 1977c, with additional data).

(Figure 2.44) Typical Loch Tay Limestone lithology of thinly bedded metalimestone interbedded with dark grey metamudstone. A strongly boudinaged quartzofeldspathic vein occupies the centre of the photograph. [NR 8683 7123], South Bay, Barmore Island. Hammer shaft is 60 cm long. (Photo: P.W.G. Tanner.)

(Figure 2.45) Map of the area north-east of Loch Avich that includes the outcrop of the Loch Avich Lavas Formation (after Borradaile, 1977).

(Figure 2.46) Basaltic andesite pillow lavas at An Cnap, Loch Avich, viewed to the south-east [NM 9544 1586]. Hammer shaft is 35 cm long. (Photo: E.K. Hyslop, BGS No. P 726591.)

(Figure 2.47) Map of the Loch Skerrols Thrust on the east side of Loch Gruinart, Isle of Islay showing the Bun-an-Uillt GCR site (after Fitches and Maltman, 1984).

(Figure 2.48)

(a) The main exposure of cataclastic rocks within the Blackrock Grit Formation, below the Loch Skerrols Thrust, [NR 2950 6930], c. 300 m south-west of Bun-an-Uilt, Islay. Scale is 5 cm long.

(b) Possible stretching lineation in the Jura Quartzite, above the Loch Skerrols Thrust [NR 2947 6919]. Scale is 5 cm long.

(Photos: P.W.G. Tanner.)

(Figure 2.49) Map of north-western Islay showing outcrops of the Colonsay Group and its basement of Rhinns Complex, modified after Stewart and Hackman (1973) and Muir et al. (1995).

(Figure 2.50) Topographical expression of basement–cover contact c. 1 km south-west of Kilchiaran Bay, north-west Islay. Gritty metasandstones of the Eilean Liath Grit Formation of the Colonsay Group to the right of the inlet are separated from highly sheared feldspathic gneisses of the Rhinns Complex to the left by the Kilchiaran Shear-zone, which controls the line of the inlet. Inset shows the strongly sheared rocks in the contact zone; spirit level is 5 cm long. (Photos: P.W.G. Tanner.)

(Figure 3.1) Map of the Central Grampian Highlands, showing Dalradian subgroups, major structures including the Boundary Slide and locations of GCR sites. Only areas described in Chapter 3 are ornamented. * On the limbs of the late Errochty Synform, to the north of Schiehallion, highly attenuated condensed sequences of the Lochaber and Ballachulish subgroups, too thin to be shown at this scale, are present in the Boundary Slide-zone.

GCR sites: 1, River Leven Section, 2 Nathrach, 3 Rubha Cladaich, 4 Tom Meadhoin and Doire Ban, 5 Stob Ban, 6 St John’s Church, Loch Leven, 7 Onich Dry River Gorge and Onich Shore Section, 8 Ardsheal Peninsula, 9 South Coast, Lismore Island, 10 Camas Nathais, 11 Port Selma, Ardmucknish, 12 River Orchy, 13 A9 Road Cuttings and River Garry Gorge, 14 Creag nan Caisean–Meall Reamhar, 15 Meall Dail Chealach, 16 Strath Fionan, 17 Tempar Burn, 18 Allt Druidhe, 19 Slatich, 20 Ben Lawers, 21 Craig an Chanaich to Frenich Burn, 22 Auchtertyre, 23 Ben Oss.

Faults: BBF Bridge of Balgie Fault, ELF Ericht–Laidon Fault, GGF Great Glen Fault, LTF Loch Tay Fault, TF Tyndrum Fault.

F1 and F2 folds: AS Appin/Cuil Bay Syncline, AHA Airds Hill Anticline, BCS Beinn Chuirn Synform, BDS Beinn Donn Syncline, BLA Ben Lui Antiform, BSA Beinn Sgluich Anticline, BUS Beinn Udlaidh Syncline, BWA Blackwater Antiform/Treig Syncline, BWS Blackwater Synform, CA Clunes Antiform, IA Inverlair Antiform, KA Kinlochleven Antiform, LDS Loch Dochard Syncline, MRS Meall Reamhar Synform, RA Ruskich Antiform, SBS Stob Ban Synform.

F3, F4 and later folds: BA Bohespic Antiform, BLS Ben Lawers Synform, DD Drumochter Dome, ES Errochty Synform, TM Trinafour Monoform.

(Figure 3.2) Comparison of Dalradian successions in the Loch Leven and Schiehallion (Strath Fionan) areas.

(Figure 3.3)

(a) Map of the Loch Leven area, showing outcrops of the main stratigraphical units, major structures and locations of GCR sites. BS Ballachulish Syncline, BaSl Ballachulish Slide, FWSl Fort William Slide

(b) Diagrammatic profile of the area shown in (a), looking up-plunge of F1 folds and showing position of GCR sites. Key, abbreviations and horizontal scale as in (a).

(Figure 3.4)

(a) Map of the Schiehallion–Loch Tay area, showing outcrops of the main stratigraphical units, major structures and locations of GCR sites.

(b) Cross-section of the Schiehallion–Loch Tay area, showing positions of GCR sites. Key, abbreviations and horizontal scale as in (a).

(Figure 3.5) Map of the River Leven section east of Kinlochleven.

(Figure 3.6) Near-vertical bedding in the Binnein Quartzite, on a horizontal surface in the River Leven at [NN 1910 6186]; the cross-sets young to the west (top of photograph). Coin is 20 mm diameter. (Photo: J.E. Treagus.)

(Figure 3.7) Map of the area around the Nathrach GCR site, showing the boundary between the Binnein Quartzite and the Binnein Schist on the two limbs of the F1downward-facing Mamore Syncline. At localities A, B and C, relations between bedding and the three cleavages are shown, as appropriate. The relation of bedding to the direction of younging is shown at localities along the boundary as well as at localities A and C, within the Binnein Schists.

(Figure 3.8) Thinly-bedded quartzites and semipelites in the Binnein Schists, tightly folded by F2 folds that plunge steeply to the north-east at locality A, (Figure 3.7) in the Nathrach GCR site. Coin is 25 mm diameter. (Photo: J.E. Treagus.)

(Figure 3.9) Semipelites interbedded in the Binnein Quartzite, as seen on a surface sloping gently to the south-east (bottom right) at locality B, (Figure 3.7) in the Nathrach GCR site. Cross-bedding near the top left corner youngs to the south-east and faces down on the axial-planar fabric of the minor folds; these folds, which are of D1 age, plunge at 40° to the north-east and verge to the north-east. Not clear in the photograph is the S2 crenulation cleavage, which cross-cuts the F1 folds parallel to the length of the pencil. Pencil is 15 cm long. (Photo: J.E. Treagus.)

 

(Figure 3.10) Map of the coastal section at the Rubha Cladaich GCR site, showing the outcrops of the Glen Coe Quartzite, Binnein Schists and Binnein Quartzite. Principal exposures are outlined.

(Figure 3.11) D2 folds and cleavage in the Binnein Schists at the Rubha Cladaich GCR site. F1 folds can be seen, for instance, at the tip of the pencil. Pencil is 10 cm long. (Photo: J.E. Treagus.)

(Figure 3.12) Regional geological context of the Tom Meadhoin and Doire Ban GCR site. After Roberts and Treagus (1977b, figure 5).

(Figure 3.13) Map of the Stob Ban GCR site. After Roberts and Treagus (1977b, figure 5).

(Figure 3.14) Stob Ban (left) viewed from the east, showing the Binnein Quartzite dipping to the north-west (away from the camera) on the south-east limb of the Stob Ban Synform. In the centre, the area of the Stob Ban GCR site, beds of Leven Schists and Ballachulish Limestone dip to the south-east on the north-west limb of the synform. (Photo: D. Stephenson, BGS No. P 726592.)

(Figure 3.15) Map of the Loch Leven shore section at St John’s church after Bailey (1960).

(Figure 3.16) View looking north-east along the outcrop of the Ballachulish Slide on the shore of Loch Leven, near St John’s church. The slide occurs beneath the hammer shaft and can be traced along the black dotted line. To its right is the Ballachulish Limestone; immediately left of the hammer, and for about one metre beyond, are a few centimetres of quartzitic Leven Schists; the remainder of the exposure left of the slide is a NE-trending dyke. Hammer shaft is 30 cm long. (Photo: J.E. Treagus.)

(Figure 3.17) Map of the Onich Shore Section and the south-west end of the Onich Dry River Gorge GCR sites. Areas outlined by dotted lines are exposures discussed in the text, showing typical measurements of bedding (with direction of younging where appropriate) and plunge (and vergence where appropriate) of F1 minor folds.

(Figure 3.18) Generalized structural profile of the F1 Appin Syncline for the area containing the Onich Dry River Gorge, Onich Shore Section and Ardsheal Peninsula GCR sites, looking up-plunge to the north-east at about 25°. Use has been made of data from the Onich shore section as well as the profile drawn of the Ardsheal area by Treagus and Treagus (1971, figure 2). Data from localities 1–5 of the Ardsheal Peninsula GCR site are shown in the top left corner of the profile.

(Figure 3.19)

(a) Cross-sets, younging to the north-west (top left) on a horizontal surface of near vertical-dipping Appin Quartzite at Caigean Mor [NN 0437 6105] on the Onich shore section. Lens cap (top left) is 4 cm diameter.

(b) View to the north-east of SE-verging F1 folds of a 10 cm-thick limestone bed, and of thinner adjacent beds, in the Appin Phyllite on the Onich shore section at [NN 036 612], 300m SW of the school. Coin (centre) is 30 mm in diameter.

(Photos: J.E. Treagus.)

(Figure 3.20) Map of the Appin Syncline on the Ardsheal Peninsula. Numbers relate to localities discussed in the text. After Treagus and Treagus (1971).

(Figure 3.21)

(a) Bedding in the Cuil Bay Slates shows upward grading, crossed by upright S1 cleavage. View to the south-west, down the plunge of a F1 fold hinge from [NM 972 554], Rubha Beag, Ardsheal Peninsula. Lens cap is 5 cm in diameter.

(b) F1 folds, verging north-west and plunging gently to the south-west in phyllitic semipelites and psammites near the top of the Appin Quartzite on Rubha Mor, Ardsheal Peninsula [NM 9640 5565]. The fanning S1 cleavage can be seen in the semipelite bed in the centre. Figures for scale.

(Photos: J.E. Treagus.)

(Figure 3.22) Map of southern Lismore Island, showing the ‘units’ of the Lismore Limestone Formation and sedimentary cycles within the Middle unit as mapped by Hickman (1975, 1978). The traces of the major folds are also shown: A and B form a major F2 fold-pair, C is a major F1 syncline. The cross-section (after Hickman, 1978) illustrates the major folds and the relation of the (schematic) vergence of the F2 minor folds.

(Figure 3.23) Open F2 minor folds, verging north-west in the Lismore Limestone Formation south-west of Miller’s Port [NM 812 372]; view to the south-west. Figure is 1.5 m tall. (Photo: J.E. Treagus.)

(Figure 3.24) Map of the Lochnell Peninsula and adjoining area, north of Oban, modified from BGS 1:50 000 Sheet 45E (Connel). It shows the regional setting of both the Camas Nathais and Port Selma, Ardmucknish GCR sites (labelled inset boxes), and the line of the Benderloch Slide.

(Figure 3.25) Detailed map of an area at the head of Camas Nathais (see inset on (Figure 3.24)), based upon a survey by P.W.G. Tanner using GPS for location. The irregularly shaped Palaeogene dykes and sheets provide a guide to location on this featureless rock platform. The map shows the relationship of the rock sequence and structure in the hanging wall of the Benderloch Slide (S), to those in the footwall.

(Figure 3.26) The Benderloch Slide at Camas Nathais, as seen looking north from locality 1, (Figure 3.25). The slide-plane dips steeply to the north-west and separates graphitic pelite (g) above, from a strongly boudinaged and disrupted unit of orange-weathering dolostone (d) below. To the right of and beneath the dolostone is the intensely fractured Baravullin Quartzite (q).

Inset: Lineations in the graphitic pelite just above the slide, as seen looking in the direction of the arrow in the main photo. Two sets of steeply plunging lineations lie in the plane of the phyllitic cleavage The lineation plunging steeply to the left (north) is the stretching lineation associated with the slide movement, and it is crossed by later crenulation lineations and kink bands plunging to the right (south).

(Photos: P.W.G. Tanner.)

(Figure 3.27) Map of the Port Selma, Ardmucknish area showing the distribution of breccia (B1-5) and interbreccia (IB3, IB4) beds belonging to the Selma Breccia, and their relationship to the Selma Black Slates (modified from Litherland, 1982). Structural interpretation by P.W.G. Tanner.

(Figure 3.28) The Selma Breccia as seen on the coast at locality 1, (Figure 3.27), showing the variations in clast type and shape within part of breccia units B1-B3 (m, mudstone raft). The direction of view is to the south-east, with the longest dimensions of the clasts being generally aligned parallel to the NE-trending slaty cleavage. (Photo: P.W.G. Tanner.)

(Figure 3.29) Map of the closure of the F2 Beinn Udlaidh Syncline in Glen Orchy. The curved axial trace of this fold is due to the intersection of the gently dipping axial surface with the irregular topography, and does not reflect the curvilinear hinge as described in the text or later deformation. Equal-area stereographic projections for some of the structural data are shown. Stereoplot (a) shows the poles to the axial planes of minor folds related to the syncline, together with their computed mean orientation as a great circle (solid line). Stereoplot (b) shows the orientations of stretching lineations (solid triangles; N=41) and minor fold hinges (open circles; N=107), related to the major syncline. The solid line represents the computed best-fit plane containing the fold hinges.

(Figure 3.30) Z-shaped vergence shown by main-phase minor folds, which plunge to the south on the upper limb of the F2 Beinn Udlaidh Syncline in the River Orchy. The structures are seen looking due south from the dam at locality 1, (Figure 3.29), during low-water conditions. The hammer shaft is 78 cm long. (Photo: P.W.G. Tanner.)

(Figure 3.31) Stacked fold hinges of minor folds (‘fold mullions’) with neutral vergence in the hinge-zone of the F2 Beinn Udlaidh Syncline in the River Orchy at locality 2, (Figure 3.29). The structures are viewed from the south-east, and the hammer shaft is 78 cm long. (Photo: P.W.G. Tanner.)

(Figure 3.32) The major structures of Glen Garry depicted in three dimensions and showing the localities 1–7 that are described in the text. Below is a map of the Glen Garry section showing the A9 road, the River Garry and the positions of the numbered localities. Adapted from Thomas (1988, figure 1.2).

(Figure 3.33) Cross-bedded laminated schistose psammites at the Stalcair Cut on the A9 road (locality 1). The beds young to the right (south-east), and thus the F2 fold is downward facing. The masonry buttress is c. 4 m high. See Thomas (1988, figure 1.5) for an annotated sketch of this view. (Photo: P.R. Thomas.)

(Figure 3.34) The exposed hinge of the Bohespic Antiform in the A9 road cut near the Allt Chrom, looking north (locality 4). Car gives scale. See Thomas (1988, figure 1.4) for an annotated sketch of this view. (Photo: P.R. Thomas.)

(Figure 3.35) Downwards- and SE-facing F2 folds on the rock faces of the Clunes Cut on the A9 road, looking north-east (locality 6). Height of section about 8 metres. (Photo: J.E. Treagus.)

(Figure 3.36) Sedimentary dykes of schistose semipelite in schistose psammite (top, centre), cross-lamination and slump folds in the River Garry, Struan (locality 7). Beds young to the right (south-east) on the steep overturned limb of an F2 fold. The compass is c. 5 cm in diameter. (Photo: P.R. Thomas.)

(Figure 3.37) Map of the Creag nan Caisean–Meall Reamhar GCR site after Thomas (1965). Minor intrusions are not shown.

(Figure 3.38) Exposure near the forestry road on the south flank of Creag nan Caisean at [NN 771 601], where a strong penetrative schistosity (S1) cuts steeply dipping, cross-laminated (SS) schistose psammite. The hand lens is c. 3 cm in diameter. (Photo: P.R. Thomas.)

(Figure 3.39)

(a) Structural map of the Trinafour Monoform and the adjacent area around Meal Dail Chealach and Loch Errochty. AC Allt Culaibh Antiform, AS Allt Sleibh Antiform, CS Croftnagowan Synform, ML Meal na Leitreach Synform, SC Sron Con fold-pair, TM Trinafour Monoform.

(b) Schematic profile view of the map in (a), looking east-south-east. Adapted from Thomas (1980).

(Figure 3.40) Minor Ft monoformal fold related to the Trinafour Monoform on the west flank of Sron Chon [NN 680 668], north of Loch Errochty. The fold is plunging at 20° to 165° (away from the camera) and is cut by a small thrust plane. The hammer shaft is 30 cm long. (Photo: P.R. Thomas.)

(Figure 3.41) Geology of the Strath Fionan area based on mapping by J.E. Treagus and P.A.R. Nell. After BGS 1:10 000 sheet NN75NW (1997) and Treagus (2000, figure 4).

(Figure 3.42) Thinly bedded Beoil Quartzite in Strath Fionan exhibits an F2 fold-pair, verging south in the centre of the picture. To the right of the F2 synform is a tight F1 closure folded by another F2 antiform. View to the east from [NN 721 576, c. 300 m north-east of Lochan an Daimh. Hammer head is 15 cm long. (Photo: J.E. Treagus.)

(Figure 3.43) The lower limestone of the Blair Atholl Dark Limestone and Dark Schist Formation in the hinge-zone of an F2 fold in Strath Fionan. View to the south-east from [NN 717 570], c. 200 m south-west of Lochan an Daimh. Outcrop is about 10 m wide. (Photo: J.E. Treagus.)

(Figure 3.44) Map of the Tempar Burn area based on mapping of P.A.R. Nell (BGS 1:10 000 sheet NN65NE).

(Figure 3.45) Exposure of a boulder bed close to the Tempar Burn track at [NN 696 565], showing elongation of stones parallel to a vertical cleavage; the holes are weathered-out dolomitic clasts, whilst the stones that are proud are of granite, quartzite and biotite-muscovite semipelite (e.g. large clast to the right of the hammer shaft). Hammer shaft is 30 cm long. (Photo: J.E. Treagus.)

(Figure 3.46) Map of the lower part of the Allt Druidh, after P.A.R. Nell (BGS 1:10 000 sheet NN65NW).

(Figure 3.47) Map of the hinge-zone of the Ruskich Antiform in the Slatich area based on mapping of P.A.R. Nell (BGS 1:10 000 sheet NN64NW). Adapted from Treagus, 2000, figure 7.

(Figure 3.48) Cut surface of finely bedded quartzite and amphibolite of the Farragon Formation, c. 800 m east-north-east of Slatich, Glen Lyon [NN 6407 4778]. Isoclinal F1 folds (arrowed) are refolded by more-open F2 folds. Scale bar in centimeters. (Photo: J.E. Treagus.)

(Figure 3.49) Map and cross-section (A–B) of the area south-west of the Ben Lawers mountain range, showing localities 1–5, described in the text. Boundaries are based on the original Geological Survey 1:63 360 Sheet 46 (1900), except those of the Farragon Volcanic Formation. The latter boundaries are extrapolated from observations at localities 2 and 4, assuming a constant thickness. Structural data is from Nell (1984) and Treagus (1964b and unpublished). The geometry of folds shown at the key localities on the cross-section are representative of the vergence of the F2 folds.

(Figure 3.50) Cut surface of a typical calcareous schist of the Ben Lawers Schist Formation from the south-east shore of Lochan na Lairige [NN 601 393]. The S4 crenulation cleavage is well developed in the lower part of the specimen, while the calcareous quartzite bed near its top exhibits open F4 folding, which at the left-hand edge refolds a tight F2 fold-pair. Scale in centimetres. (Photo: J.E. Treagus.)

(Figure 3.51) Map of Creag an Chanaich and the area of opencast pits. Mapping west of easting 8145 is based on Moles (1985a) and Treagus (2000); to the east it is based on unpublished mapping by J.M. Maclachlan and N.J. Butcher. Compilation and structural observations by J.E Treagus.

(Figure 3.52) Schematic down-plunge profile view of major and minor F2 and F3 folds in the area of the Craig an Chanaich mine and opencast pits. A plunge of 25° to 255° is assumed; fault movement restored. After Pattrick and Treagus (1996, figure 6).

(Figure 3.53) The opencast workings at Creag an Chanaich, in which Ben Eagach Schist (dark area, centre) is exposed in the core of an F2 synform within the stratiform baryte. Cliff exposure is 10 m high. (Photo: J.E. Treagus.)

(Figure 3.54)

(a) Map of the Auchtertyre area.

(b) Equal-area stereographic projection of poles to S2 planes and hinges of F2 folds (the range of plunge of folds with strongly curvilinear hinges is shown by the dashed lines). See text for explanation.

(Figure 3.55) Curvilinear F2 fold hinge in the Allt Gleann a’ Chlachain, Auchtertyre GCR site. Hammer head is 15 cm long. (Photo: J.E. Treagus.)

(Figure 3.56) Refolded ?F1 folds in the Allt Gleann a’ Chlachain, Auchtertyre GCR site. Pen is 13 cm long. (Photo: J.E. Treagus.)

(Figure 3.57) Map of the Ben Oss Fault-zone with the Tyndrum Fault immediately to its south-east, occupied by a microdiorite dyke. The outcrop of the Ben Lawers Schist (ornamented) is shown between the two faults and its margin with the Ben Lui Schist is shown to the north-west of the Ben Oss Fault. The inset shows, (a) the left-lateral movement on the Tyndrum Fault and (b) the subsequent locking by the dyke and right-lateral movement transferred to the Ben Oss Fault.

(Figure 3.58) Vertical aerial photograph of the northern flank of Ben Oss, showing the Ben Oss Fault (stream gully in centre with large arrows at each end) and fractures orientated at 20° anticlockwise to the fault on its north-west side (indicated by small arrows). See text for explanation. (Aerial Photograph © Getmapping.)

(Figure 4.1) Map of the Highland Border region showing the main stratigraphical divisions, axial plane traces of major folds, and locations of the GCR sites. Only areas described in Chapter 4 are ornamented; outcrop width of the Tayvallich Subgroup is exaggerated in places. NB south-west of the Loch Tay Fault, the pelitic rocks shown in the core of the Aberfoyle Anticline are mostly assigned to the Aberfoyle Slate Formation, which is assumed to be relatively low in the Southern Highland Group; north-east of the Loch Tay Fault, the pelitic rocks are at lower structural levels and hence are in higher parts of the succession, such as the Birnam Slate and Grit Formation (see (Figure 4.2)). Based on BGS 1:250 000-scale maps and modified by P.W.G. Tanner in the light of recent work.

Lines of section AA’– GG’ refer to (Figure 4.4).

Axial plane traces of folds: AA Aberfoyle Anticline (F1–F2), BLA Ben Ledi Antiform (F1–F2), BVS Ben Vane Synform (F1–F2), CA Cowal Antiform (F4), HBD Highland Border Downbend (F4).

Faults: BBF Bridge of Balgie Fault, HBF Highland Boundary Fault, LTF Loch Tay Fault, TF Tyndrum Fault.

GCR sites: 1 Ardscalpsie Point, 2 Cove Bay to Kilcreggan, 3 Portincaple, 4 Bealach nam Bo, 5 Duke’s Pass, 6 Keltie Water, Callander, 7 Little Glen Shee, 8 Craig a’ Barns, 9 Rotmell, 10 Glen Esk, 11 Garron Point to Muchalls.

(Figure 4.2) Stratigraphical columns (not to scale) showing variations in Southern Highland Group stratigraphy along the length of the Highland Border region and variations across the strike, where present. N.B. in the Cowal to Loch Lomond area, equivalent formations on the inverted north-west limb and the right-way-up south-east limb of the Aberfoyle Anticline have different names and are shown separately. Although these do reflect some facies variations, the reason is largely historical, dating back to the period before the anticline was recognized. Capital letters in column headings refer to cross-sections in (Figure 4.4). GCR sites are numbered as on (Figure 4.1).

(Figure 4.3) ‘Gneiss Rock at Glenfinlas’, 1853-54 (pen, wash and gouache on paper), John Ruskin (1819-1900) © Ashmolean Museum, University of Oxford. This picture took several months to complete and lovingly and precisely depicts the tortuous shapes wrought by weathering of the strongly developed S1/S2 cleavage typical of Southern Highland Group rocks south-east of the Highland Border Downbend. The site is in the River Turk, by Brig O’Turk (Greive, 1996), a few hundred metres north of the northern boundary of (Figure 4.18).

(Figure 4.4) True-scale serial sketch cross-sections across the Tay Nappe and Highland Border Downbend, as viewed to the south-west in the plunge direction of the downbend. Limits of cross-sections and lines of section as shown on (Figure 4.1) are notional and do not reflect current level of erosion.

AA’ Isle of Bute to Loch Fyne.

BB’ West side of Loch Lomond.

CC’ Aberfoyle to Loch Katrine. (after Section 1, BGS 1:50 000 Sheet 38E, Aberfoyle, 2005).

DD’ Callander. (unpublished cross-section by J.R. Mendum).

EE’ Dunkeld. (after (Figure 4.24)a).

FF’ Glen Shee. (after sections 1, 2 and 4, BGS 1:50 000 Sheet 56W, Glen Shee, 1999).

GG’ Stonehaven. (after (Figure 4.33)).

Positions of GCR sites, projected onto the nearest equivalent cross-section, are numbered as on (Figure 4.1).

(Figure 4.5) A composite figure prepared from C.T. Clough's field sketches, as reproduced in the Geological Survey’s Cowal memoir (Clough, in Gunn et al., 1897, figs 12 and 13). The individual sketches are arranged diagrammatically with respect to their inferred position on the Cowal Antiform. It is clear from these sketches that Clough understood how to identify and unravel the effects of polyphase deformation some sixty years before John Ramsay demonstrated it at Glenelg (Ramsay, 1958).

(Figure 4.6) Map showing the bedding-cleavage relationships in the Dalradian rocks immediately north-west of a splay of the Highland Boundary Fault, north of Ardscalpsie Point, Isle of Bute. A–F, reference points on the line of cross-section shown in (Figure 4.8).

(Figure 4.7)

(a) An inland exposure at Ardscalpsie Point [NS 0440 5766], showing the bedding-cleavage relationship found typically on the upper limb of the Tay Nappe at this GCR site. Bedding, which is parallel to the hammer shaft, is cut by the spaced S1 cleavage (seen as etched lines on the surface) that dips at a more-gentle angle to the south-east (right on photo). Hammer shaft is 60 cm long. (Photo: P.W.G. Tanner.)

(b) Photomicrograph showing the relatively undeformed nature of the D1 metasandstone microlithons which, together with the intervening thin dark cleavage domains, constitute the S1 cleavage in (a).

(Photos: P.W.G. Tanner.)

(Figure 4.8) A true-scale, NNW–SSE-trending cross-section, prepared from field sketches, of the structures along the line A—F in (Figure 4.6), Ardscalpsie Point GCR site.

(Figure 4.9) Map of the southern end of the Rosneath peninsula, including the Cove Bay to Kilcreggan GCR site, based on BGS 1:50 000 Sheet 30W (Greenock, 1990).

(Figure 4.10)

(a) Centimetre-wide microlithons, separated by narrow dark anastomosing cleavage domains which, together form the main, SE-dipping, S2 fabric in the metagreywacke unit of the Dunoon Phyllite Formation near Barons Point [NS 223 808]. The spaced S1 fabric can be clearly seen locally within the microlithons, frozen in the act of transformation to S2. The L2 intersection lineation occurs as a ribbon lineation on the main fabric surface.

(b) Photomicrograph of the D2 microlithons in (a), reworking S1 pressure-solution stripes (shown in their original state in (Figure 4.7)b).

(Photos: P.W.G. Tanner.)

(Figure 4.11)

(a) Location map of the Portincaple GCR site. Bedrock is the Beinn Bheula Schist Formation, cut by the few dykes shown. A–B, C–D, lines of cross-section for (b).

(b) True-scale field sketch of a vertical cross-section, viewed approximately down-plunge for F4, across the southern part of the hinge-zone of the Highland Border Downbend (F4). The main fabric in these rocks is a centimetre-spaced pressure-solution (or dissolution) cleavage (S2).

(c) Equal-area stereographic projection showing poles to the S2 fabric that defines a best-fit great circle whose π axis plunges at 10° to 079°, parallel to the major F4 fold axis of the Highland Border Downbend.

(Figure 4.12)

(a) A vertical rock face in the Bheinn Bheula Schist Formation at Portincaple [NS 2297 9327], viewed to the north-east (054°), showing asymmetrical, Z-shaped F3 folds on the southern limb of the Highland Border Downbend. The D3 structures deform the main S2 spaced fabric; the poorly developed minor upright F4 folds are accompanied by a near-vertical, crenulation cleavage that, although restricted to the pelitic seams, is clearly imprinted on and hence post-dates all of the other structures. Note the local preservation of the S1 fabric within the S2 microlithons. (Photo: P.W.G. Tanner.)

(b) An explanatory outline drawing of (a).

(c) Photomicrograph of the S4 crenulation cleavage at X on (b). (Photo: P.W.G. Tanner.)

(Figure 4.13) Cross-section from Callander due north to Loch Tay. The section continues the Flat Belt from the southern end of the section in (Figure 3.3)b and shows the position of the Keltie Water (KW), Bealach nam Bo (BB)and Dukes Pass (DP) GCR sites within the Steep Belt created by the F4 Highland Border Downbend. The assumption is made that there is a single continuous unit of ‘green beds’.

(Figure 4.14) Map of the area around Bealach nam Bo, Loch Katrine, Trossachs. Based upon mapping by the British Geological Survey, 19961998.

(Figure 4.15) Sedimentological log through ‘green beds’ in the Loch Katrine Volcaniclastic Formation, exposed in cliffs at Bealch nam Bo. Adapted from Burt (2002).

(Figure 4.16) F1 folds with axial planar cleavage picked out by quartz veins in ‘green beds’ and cleaner metasandstone in the Loch Katrine Volcaniclastic Formation at Bealach nam Bo [NN 478 075]. Lens cap is 50 mm diameter. (Photo: C.W. Thomas, BGS No. P 726593.)

(Figure 4.17) F2 crenulation folds of the first cleavage in the Creag Innich Sandstone Formation at [NN 4777 0714], Bealach nam Bo GCR site. Lens cap is 50 mm diameter. (Photo: C.W. Thomas, BGS No. P 726594.)

(Figure 4.18) Map of the area around the Duke’s Pass, Aberfoyle. Based upon mapping by the British Geological Survey, 19961998.

(Figure 4.19) Typical F1 fold in metasandstone of the Creag Innich Sandstone Formation at [NN 5144 0344] on the Duke’s Pass, Aberfoyle. The coarse-grained base of a gritty metasandstone unit lies above the hammer head, passing down into finer grained rock towards the end of the handle. The rocks are inverted and the fold is downward facing. Hammer shaft is 36 cm long. (Photo: C.W. Thomas. BGS No. P 643897.)

(Figure 4.20) Map of the Keltie Water, Callander GCR site. Locations of photomicrographs ((Figure 4.21), a–e) and the field photograph (Figure 4.22) are indicated. The position of the putative terrane boundary between the Grampian Terrane and the Highland Border ‘exotic terrane’ (Brasier et al., 1992) is also shown for reference.

The inset map shows three structural sub-areas sited across the boundary between undoubted Dalradian rocks of the Ben Ledi Grit Formation (A), and the lower part of the Keltie Water Grit Formation, including the Transition Member (B). Sub-area C consists mainly of gritty metasandstones of the Keltie Water Grit Formation, comparable in lithology to the rocks in sub-area A. Equal-area stereographic projections for each of these sub-areas show the poles to the main cleavage, together with their computed mean orientation shown as a great circle (solid line).

(Figure 4.21) Photomicrographs of medium- to coarse-grained metagreywackes from the Keltie Water section, and a related exposure 5 km to the south-west. The photomicrographs illustrate the similarities in petrography and strain state of samples from (a) the Ben Ledi Grit Formation, (b) the Transition Member, (c) the lower part of the Keltie Water Grit Formation, above the Transition Member, (d) the Keltie Water Grit Formation above the Keltie Limestone and Slate Member and (e) the upper part of the Keltie Water Grit Formation above the Leny Limestone and Slate Member. The selected photomicrographs are representative examples chosen from over 100 thin sections and full details of the petrography were given by Tanner and Pringle (1999). Locations of samples are shown on (Figure 4.20), except for (e) which is located at [NN 6037 0858]. All photomicrographs are at the same scale with a width equivalent to approximately 4 mm. (Photos: P.W.G. Tanner.)

(Figure 4.22) Spaced S1 cleavage, with microlithons 1–3 cm thick, associated with a minor fold in gritty metasandstones of the Keltie Water Grit Formation. Section viewed to the north-east. This exposure (see (Figure 4.20) for location) was removed totally by a recent flood. (Photo: P.W.G. Tanner.)

(Figure 4.23) Map of the Dunkeld  Pitlochry area to show the main lithostratigraphical units, the main elements of the structure and the locations of the Little Glen Shee, Craig a’Barns and Rotmell GCR sites. Adapted from Rose and Harris (2000, figure 2).

(Figure 4.24)

(a) Schematic cross-section from Pitlochry to Dunkeld to show the location of (Figure 4.24)b, and the position of the Little Glen Shee, Craig a’Barns and Rotmell GCR sites in relation to the Tay Nappe.

(b) Schematic cross-section across the Flat Belt (FB), the Highland Border Downbend (HBD), the Highland Border Steep Belt (HBSB) and the Highland Boundary Fault (HBF) to show the position of the Little Glen Shee, Craig a’Barns and Rotmell GCR sites in relation to the detailed geology of the district. Adapted from a drawing by P.T.S. Rose.

(Figure 4.25) Geological relationships at the crag that comprises the Little Glen Shee GCR site, to show the geometry of the folds and the general direction of younging of the beds. Insets 1 and 2 show the detail of relations between bedding and the refracted cleavage on alternate fold limbs. Locations of photographs, (Figure 4.26)a and (Figure 4.26)b, are shown. Adapted from a field sketch by P.W.G. Tanner with insets from P.T.S. Rose.

(Figure 4.26) Detailed sedimentological and structural features of the Little Glen Shee GCR site at locations shown in (Figure 4.25).

(a) Cleavage types and refraction related to rock type. A spaced cleavage (S1p) occurs in metasandstones in the centre of the photo and is refracted as it passes into a slaty cleavage (S1) in metasiltstones on either side. To the right there is a sharp lithological change at the base of the metasandstone unit, but to the left the more gradual refraction brings out grading from one lithology into another. Younging is to the left (north-north-west). Coin is 1.2 cm in diameter.

(b) Detail of the minor fold-pair diagrammatically represented in (Figure 4.25) and discussed in the text. Coin is 1.2 cm in diameter.

(Photos: A.L. Harris.)

(Figure 4.27) Location map of the Craig a’Barns GCR site, showing the position of localities A–D described in the text and the approximate trace of the Highland Border Downbend (HBD).

(Figure 4.28) Detailed structural relationships at the Craig a’Barns GCR site.

(a) Sketch taken from a photograph of the fold at locality B on (Figure 4.27), discussed in the text. A metasandstone bed contains tight F2 folds of S1p showing consistent vergence on opposite limbs of the Highland Border Downbend-related, step-like open fold.

(b) The association between the Highland Border Downbend-related crenulation cleavage (overdrawn straight lines, labelled S4) and folded bedding (S0), seen at or near the core of the downbend at locality C on (Figure 4.27). At the top of the photograph, bedding is essentially parallel to both S1 and S2 but in the bottom left, S1p is at a distinct angle to bedding. Looking north-east, width of exposure about 60 cm. (Photo: A.L. Harris.)

(c) Detail of the crenulation cleavage related to the Highland Border Downbend at locality C on (Figure 4.27). Looking north-east, width of exposure 20 cm. (Photo: A.L. Harris.)

(Figure 4.29) Intense F2 folds of the S1p cleavage at the Rotmell GCR site. Note the contrast in thickness between S1p microlithons in the hinges of the F2 folds and those on the limbs. Top-to-the-right (south-east) shear is inferred. Looking north-east at [NO 0128 4118]. Field of view is approximately 50 cm high. (Photo: J.E. Treagus.)

(Figure 4.30) Map of lower Glen Esk showing the full range of regional metamorphic zones first erected by Barrow (1893, 1912). Redrawn from Harte (1987), with modifications based on BGS 1:50 000 Sheet 66W (Aboyne, 1995).

(Figure 4.31) Photomicrographs (a–d, f) and one field photo (e) illustrating the sequence of Barrow’s Zones, as represented in the Glen Esk GCR site. Rocks photographed come from the localities described in the text, except for the sillimanite zone (f), which is from a locality by Glen Effock (described by Harte, 1987). All photomicrographs are at the same scale with a width equivalent to approximately 4.5 mm. (Photos: B. Harte.)

(a) Chlorite Zone. Principal minerals are quartz, white mica, chlorite and opaques (iron oxide and sulphide). The bedding and main cleavage are approximately parallel to the top edge of photo, and the upper (darker) half of the photo represents a chlorite-rich layer, whilst the lower part is more quartz rich. A later cleavage is visible as pale (white mica-rich) seams cutting obliquely across the chlorite-rich layer.

(b) Biotite Zone. Biotite porphyroblasts (Bt) overgrow a finer grained matrix of quartz, white mica, chlorite and opaque iron minerals. The bedding and main cleavage are roughly parallel to the top edge of the photo.

(c) Garnet Zone. Biotite (Bt) and garnet (Grt) porphyroblasts in a finer grained matrix of quartz, white mica, chlorite and opaque iron minerals. Areas in the matrix richer in chlorite (Chl) have a darker appearance.

(d) Staurolite Zone. Porphyroblasts of garnet (Grt and highest relief), staurolite(St and high relief) and biotite (Bt and moderate relief) in a matrix of quartz and muscovite with a small amount of opaque iron minerals.

(e) Kyanite Zone. Field photo of a vein dominantly of quartz and kyanite; the label is in the centre of a rosette of kyanites. Penknife is 10 cm long.

(f) Sillimanite Zone. A large (2 mm) porphyroblast of garnet (Grt) in the centre, together with smaller porphyroblasts of kyanite (Ky) and staurolite (St). The ‘Sill’ label is on a cluster of sillimanite fibres (fibrolite). Darker areas to the left and right of the garnet are of biotite intergrown with fibrolite. Pale areas are dominated by muscovite and quartz.

(Figure 4.32) Location of the coast section in Southern Highland Group rocks from Garron Point to Muchalls, north of Stonehaven, showing the principal structural and metamorphic features. After BGS 1:50 000 Sheet 67 (Stonehaven, 1999), with approximate locations of metamorphic mineral isograds based on Harte et al. (1987, figure 2a).

(Figure 4.33) Partly schematic structural cross-section of the coast north of Garron Point, Stonehaven, showing the contrast in dip of bedding in the Flat and Steep belts, the principle F1 and F4 folds and the limits of D2 and D4 deformation in metasandstones. Structures observed on the coast have been projected onto the line A–A′ shown on (Figure 4.27). Section is true scale (no vertical exaggeration). After BGS 1:50 000 Sheet 67 (Stonehaven, 1999).

(Figure 4.34) Cleavage/bedding relationships in Southern Highland Group rocks of the Garron Point to Muchalls GCR site.

(a) Widely spaced S4 cleavage in calcsilicate-rock and psammite at Hall Bay [NO 8994 8985]. View to the south-west down the plunge of the F4 folds.

(b) S1 cleavage is steeper than bedding in beds that young south and are therefore inverted and downward facing on S1. Exposure at high-water mark just south of promontory at edge of main part of Perthumie Bay [NO 8908 8811]. (Photos: C.W. Thomas, BGS Nos. P 726595 and P 726596.)

(Figure 5.1) Map of the Northern Grampian Highlands showing distribution of subgroups (after Smith et al., 1999). Circled letters on the map refer to stratigraphical columns in (Figure 5.3).

GCR Sites: 1 An Suidhe, Kincraig 2 The Slochd, 3 Lochan Uaine, 4 Blargie Craig, 5 River E, 6 Garva Bridge, 7 Rubha na Magach, 8 Kinloch Laggan Road A86, 9 Allt Mhainisteir, 10 Aonach Beag and Geal-charn, 11 Ben Alder.

Abbreviations: BS Boundary Slide, ESZ Eilrig Shear-zone, ELF Ericht–Laidon Fault, FSSZ Flichity–Slochd Shear-zone, GB Glen Banchor, GOSB Geal-charn–Ossian Steep Belt, IMF Inverpattack–Markie Fault, KC Kincraig, LSZ Lochindorb Shear-zone, SF Sronlairig Fault.

(Figure 5.2) Rift basins and their bounding lineaments in the Northern Grampian Highlands (after Smith et al., 1999). Based on a simplified geological map after restoration and removal of major faults and intrusions. Solid linework shows the outline of the main subgroups (see (Figure 5.1)).

Abbreviations: MPH Meall Ptarmigan High, SOL Strath Ossian Lineament.

(Figure 5.3) Stratigraphical correlations in the Northern Grampian Highlands (after Smith et al., 1999) for the areas shown by circled letters in (Figure 5.1). Thicknesses are relative but not to scale. Blank areas in columns indicate stratigraphical breaks.

Abbreviations: AB Aonach Beag Semipelite Fm, ACH Achneim Striped Psammite Fm, AD Ardair Semipelite Fm, AP Appin Group, undivided, BAS Ben Alder succession, BSZ Blargie Shear-zone, CC Coire Cheap Semipelite Fm, CM Creag Meagaidh Psammite Fm, CNL Coire nan Laogh Semipelite Fm, CS Clachaig Semipelite Fm, DRS Drumochter succession, DS Dava Subgroup, EF Eilde Flag Formation, EL Elrick Formation, ESZ Eilrig Shear-zone, FSSZ Flichity–Slochd Shear-zone, GB Glen Buck Psammite Fm, GBS Glen Banchor Subgroup, GS Glenshirra Subgroup (undivided), IL Inverlair Psammite Fm, K Kincraig Formation, KLQ Kinlochlaggan Quartzite Fm, LL Loch Laggan Psammite Fm, LSZ Lochindorb Shear-zone, LTQ Loch Treig Schist and Quartzite Fm, NB Nethybridge Fm, PT Pitmain Semipelite Fm, PY Pityoulish Semipelite Fm, RS Ruthven Semipelite Fm, STS Strathtummel succession, TB Tarff Banded Semipelite Fm, TP Tormore Psammite Fm.

(Figure 5.4) Opposed verging fold-pairs separated by a vertical high-strain zone in psammites of the Glen Spean Subgroup in the Geal-charn–Ossian Steep Belt. North-east of Loch a'Bhealaich Leamhain, Ardverikie Forest [NN 5060 7960], 5 km north-east of the Aonach Beag and Geal-charn GCR site). S. Robertson provides a scale. (Photo: BGS No. P 508351, reproduced with the permission of the Director, British Geological Survey, © NERC.)

(Figure 5.5) Map of the area around the An Suidhe, Kincraig GCR site (after BGS 1:10 000 Sheet NH80NW, 1998)

(Figure 5.6) Generalized vertical section of strata at the An Suidhe, Kincraig GCR site.

(Figure 5.7) Interbanded metacarbonate rock and phyllitic calcareous semipelite overlain by semipelite of the Kincraig Formation, Leault Limestone Quarry [NH 8210 0638], An Suidhe, Kincraig GCR site. Hammer shaft is 35 cm long. (Photo: BGS No. P220941, reproduced with the permission of the Director, British Geological Survey, © NERC.)

(Figure 5.8) Map of the area around The Slochd GCR site(after BGS 1:10 000 sheets NH82NW and NH82SW, 1998).

(Figure 5.9) Migmatized gneissose psammite with leucosomes and incipient melt segregations, Slochd Psammite Formation, south-east of the road and rail summit at The Slochd at [NH 8370 2516]. Hammer head is 16.5 cm long. (Photo: BGS No. D 5586, reproduced with the permission of the Director, British Geological Survey, © NERC.)

(Figure 5.10)

(a) The A9 roadcut at The Slochd [NH 8366 2548]. (Photo: BGS No. D 5582, reproduced with the permission of the Director, British Geological Survey, © NERC.)

(b) Sketch of the geology seen in the A9 roadcut at The Slochd (after Piasecki and Temperley, 1988b).

(Figure 5.11) Map of the Lochan Uaine area, Strath Errick (after BGS 1:10 000 Sheet NH62SW).

(Figure 5.12) Convolute lamination and cross-lamination in the Gairbeinn Pebbly Psammite Formation, east flank of Beinn Mheadhoin [NH 607 217], near the Lochan Uaine GCR site. Lens cap is 7 cm in diameter. (Photo: BGS No. P 518573, reproduced with the permission of the Director, British Geological Survey, © NERC.)

(Figure 5.13)

(a) Map of the area around the Blargie Craig GCR site, incorporating part of the Laggan Inlier after BGS 1:10 000 sheets NN59NE NN59SE, NN69NW and NN69SW (1997).

(b) Generalized cross-section across the Laggan Inlier showing general distribution of lithologies and structure, drawn 4 km north-east of Blargie Craig, from BGS 1:50 000 Sheet 63E (Dalwhinnie, 2002).

(Figure 5.14) Glacially smoothed exposure in the Blargie Craig GCR site, showing contact between the Aonach Beag Semipelite Formation of the Appin Group (left) and the Creag Liath Psammite of the Glen Banchor Subgroup (right). The hammer shaft (35 cm long) lies along the inferred unconformity. Locality 250 m north-west of Coul Farm at [NN 5870 9425]. (Photo: BGS No. P 611930, reproduced with the permission of the Director, British Geological Survey, © NERC.)

(Figure 5.15) Map of the River E section.

(Figure 5.16)

(a) Inversely graded, matrix-supported pebbly psammite overlain by a psammite displaying a variety of cross-lamination and some dewatering structures. Beds young upwards in the photo. River E [NH 5463 1363]. Open compass is 17.5 cm long.

(b) Pebbly lag at the base of trough cross-laminated psammite. Beds young upwards in the photo. River E [NH 5458 1375]. Tape measure is 10 cm in diameter.

(c) Well-preserved sand volcano in heterolithic pink and grey psammite showing ripple lamination. Beds young upwards in the photo. River E [NH 5445 1410]. Pencil is 14 cm long.

(Photos: C.J. Banks.)

(Figure 5.17) Sedimentary log for the section in the River E at [NH 5460 1367], illustrating facies stacking pattern in pebbly psammite-dominated parts of the succession. Gms matrix-supported pebbly psammite (debris flow), Gt trough cross-laminated pebbly psammite (stream-flow reworking or longitudinal bars), Sp planar laminated psammite (sandy bar form), St trough cross-laminated psammite (sandy bar form), Cl slumped layer, E erosive base.

(Figure 5.18) Map of the area around the Geal Charn–Ossian Steep Belt after Robertson and Smith (1999), with GCR sites superimposed. B Blargie Craig, Ch Coire Cheap, G Garva Bridge, Ki Kinloch Laggan, Mh Allt Mhainisteir, RM Rubha na Magach.

(Figure 5.19) Map of the Glenshirra Dome and the area of the Garva Bridge GCR site. The overall geological setting is given in (Figure 5.18).

(Figure 5.20)

(a) Heterolithic association, Garva Bridge Psammite Formation, Allt Coire Iain Oig. Cleaning and muddying upwards cycles. The clean sand component of each cycle is invariably ripple cross-laminated. The more-muddy parts of each cycle contain thin planar beds of psammite (originally clean sand) or small gutter casts filled with heterolithic sand and mud.

(b) Numerous elongate quartz pebbles within micaceous psammite in the Gairbeinn Pebbly Psammite Member of the Garva Bridge Psammite Formation, Gairbeinn. The parting present in the psammite above this pebbly bed is tectonic rather than original bedding.

(Photos: B.W. Glover.)

(Figure 5.21) Schematic cross-section through the Glenshirra Subgroup illustrating the proposed lateral facies changes and the possible basin configuration. After Glover (1998).

(Figure 5.22) Map showing the location of the Rubha na Magach localities and the general geology of the area to the north-west of Loch Laggan. The overall geological setting is given in (Figure 5.18).

(Figure 5.23) Measured sedimentary logs for:

(a) Rubha na Magach [NN 4618 8492].

(b) lochside exposures at [NN 4653 8516]. Note the crude thinning and fining-upward cycles from thick-bedded psammite, micaceous psammite and semipelite up into thinner bedded micaceous psammite and semipelite, shown to illustrate the lithofacies present. Log (a) is c. 50 m higher in the stratigraphy than log (b).

(Figure 5.24)

(a) Complex ripple-drift cross-lamination in a thick bed of micaceous psammite at Rubha na Magach [NN 4618 8492]. Open compass is 17.5 cm long. (Photo: C.J. Banks.)

(b) Loading and convolute lamination on a thick micaceous psammite grading into semipelite. Also shows a calcsilicate pod below the notebook. Lochside exposure at [NN 4653 8516]. Notebook is 20 cm long. (Photo: C.J. Banks.)

(c) Bouma units Ta to Te in a thick psammite to semipelite bed on the Rubha na Magach promontory at [NN 4618 8492]. A basal massive psammite (Ta) passes into a lower plane bed (Tb), a cross-laminated horizon (Tc), an upper plane bed (Td) and is finally capped by semipelite (Te). Pen is 15 cm long. (Photo: J.A. Winchester.)

(Figure 5.25) Map of the area around the Kinloch Laggan Road A86 GCR site. After Robertson and Smith (1999). The wider geological setting is shown on (Figure 5.18). KLS, Kinlochlaggan Syncline.

(Figure 5.26) Typical lithofacies of the Kinlochlaggan Boulder Bed with 40 x 16 cm granite boulder in centre of view [NN 548 897]. Hammer head is 16.5 cm long. (Photo: BGS No. P 221180, reproduced with the permission of the Director, British Geological Survey, © NERC.)

(Figure 5.27) Lithostratigraphy of the area within and west of the Geal-charnOssian Steep Belt in the vicinity of the Kinloch Laggan Road, Allt Mhainisteir and Aonach Beag and Geal-charn GCR sites. After Robertson and Smith (1999).

(Figure 5.28) Map of the Allt Mhainisteir and Allt Liath nam Badan sections, south of Loch Laggan. The overall geological setting is shown in (Figure 5.18).

(Figure 5.29) Intense isoclinal folding in the Creag Meagaidh Psammite Formation adjacent to the Allt Mhainisteir Slide, [NN 5343 8535]. Hammer head is 16.5 cm long. (Photo: BGS No. P 221176, reproduced with the permission of the Director, British Geological Survey, © NERC.)

(Figure 5.30) Map of the area around the Allt Mhainisteir, Rubha na Magach and Aonach Beag and Geal-charn GCR sites. After Robertson and Smith (1999). The line of cross-section in (Figure 5.31) is shown as A–A′. AG Aonach Beag and Geal-charn GCR site, KLS Kinlochlaggan Syncline, Mh Allt Mhainisteir GCR site, RM Rubha na Magach GCR site.

(Figure 5.31) Schematic cross-section across the Geal-charnOssian Steep Belt along the line A–A' indicated on (Figure 5.30). ABS Aonach Beag Slide, CC Coire Cheap, CS Coire Sgoir, SGF Sron Garbh Fold-complex, SS Sgoir slides. After Robertson and Smith (1999). Ornaments as on (Figure 5.30).

(Figure 5.32) Annotated view south-south-west from below Diollaid a'Chairn [NN 4920 7540] to Coire Sgòir, Loch an Sgòir and Sgòr Iutharn in the Aonach Beag and Geal-charn GCR site, showing structures on the south-east edge of the Geal-charn–Ossian Steep Belt. The smaller folds are diagrammatic. Migmatization increases north-westwards in the steep belt. gPs gneissose psammite, gSp gneissose semipelite, Pe pelite, Ps psammite, Sp semipelite, LEA Lancet Edge Antiform (plunges steeply into the hillside). (Photo: BGS No. P 001217, reproduced with the permission of the Director, British Geological Survey, © NERC.)

(Figure 5.33) Looking south-west from the Allt a'Chaoil-reidhe by Culra Bothy [NN 5230 7600] to Ben Alder, Sgor Iutharn and Geal-charn. The prominent gap between Ben Alder and Sgor Iutharn is the Bealach Dubh; the Ben Alder GCR site lies to the left of the bealach and the Aonach Beag and Geal-charn GCR site is to the right. (Photo: BGS No. P 001218, reproduced with the permission of the Director, British Geological Survey, © NERC.)

(Figure 5.34) Map of the area around the Aonach Beag and Geal-charn and Ben Alder GCR sites (after Thomas, 1979). ABA Aonach Beag Anticline (F1), ABS Alder Bay Synform (F2), ACA Aisre Cham Anticline (F1), BAA Ben Alder Antiform (F2), BAAn Ben Alder Anticline (F1), BAS Ben Alder Synform (F2), BDS Bealach Dubh Synform (F3), CCA Coire Cheap Anticline (F1), CIA Coire na h’ Iolaire Antiform (F3), CLS Coire Labhair Syncline (F1), CNLA Coire na Lethchois Antiform (F3), CNLS Coire na Lethchois Synform (F3), CSA Coire Sgoir Anticline (F1), GCF Garbh Coire Fault, GCS Geal Charn Syncline (F1), KLS Kinlochlaggan Syncline (F1), LEA Lancet Edge Antiform (F3), SMA Sgairneach Mhor Antiform (F2).

(Figure 5.35) Secondary upright folding superimposed on earlier tight to isoclinal folds in Grampian Group psammites. Structural architecture is typical of that developed within the ‘Ben Alder folds’ (sensu Thomas, 1979). South-east side of Bealach Dubh, [NN 5014 7120]. Hammer shaft is 35 cm long. (Photo: C.J. Banks, BGS No. P605207.)

(Figure 5.36) Schematic cross-section, approximately true-scale, across the Aonach Beag and Geal-charn and Ben Alder GCR sites (after Thomas, 1979).

(Figure 6.1) Map of the North-east Grampian Highlands based upon BGS 1:50 000-scale maps and showing the location of Dalradian GCR sites.

GCR sites: 1 Ben Vuirich, 2 Gilbert’s Bridge, Glen Tilt, 3 Glen Ey gorge, 4 Cairn Leuchan, 5 Balnacraig, Dinnet, 6 Muckle Fergie Burn, 7 Bridge of Brown, 8 Bridge of Avon, 9 Kymah Burn, 10 Black Water, 11 Auchindoun Castle, 12 Cullen to Troup Head, 13 Fraserburgh to Rosehearty, 14 Cairnbulg to St Combs, 15 Collieston to Whinnyfold.

BS Boundary Slide, KSZ Keith Shear-zone, PSZ Portsoy Shear-zone.

(Figure 6.2) Principal stratigraphical units in the Dalradian of the North-east Grampian Highlands, adapted from Stephenson and Gould (1995, figure 10). The columns are not to scale.

(Figure 6.3)

(a) Generalized cross-section along the north coast of the North-east Grampian Highlands from Cullen to Fraserburgh showing the main structural features and dominant deformation/fold phases (Stephenson and Gould, 1995, figure 21, partly after Loudon, 1963). Stipple = the Old Red Sandstone outlier at Gardenstown. The entire section is included in the Cullen to Troup Head and Fraserburgh to Rosehearty GCR sites.

(b) Highly generalized cross-section across the Buchan Block to illustrate the broad structure as envisaged by Read (1955) as modified by Kneller (1987). The approximate locations of GCR sites relative to the structure are shown.

(Figure 6.4) Map of the Ben Vuirich Granite Intrusion and adjoining country rocks, showing the locations of the two groups of exposures (A and B) which comprise the GCR site. g exposure of pelitic schist with garnet over 2 cm across.

(Figure 6.5) Hornfels associated with the Ben Vuirich Granite, with centimetre-scale, altered porphryoblasts of contact metamorphic cordierite (pale grey), dotted with small garnets (white) that formed during the subsequent D2 regional metamorphism. (Locality A, (Figure 6.4)). (Photo: P.W.G. Tanner.)

(Figure 6.6) Xenoliths of banded quartzose psammite and pelite in the Ben Vuirich Granite at locality B, (Figure 6.4). See text for explanation. The scale is 5 cm long. (Photo: P.W.G. Tanner.)

(Figure 6.7) Map of the area around the Gilbert’s Bridge GCR site, based upon the BGS 1:50 000 Sheet 55E (Pitlochry, 1981).

(Figure 6.8) Map of the area around lower Glen Ey adapted from the BGS 1:50 000 Sheet 65W (Braemar, 1989). In this area most of the information used for the BGS compilation was taken from Upton (1983).

(Figure 6.9) Schematic structural cross-section across the area between Deeside and Glen Shee. Reproduced from Upton (1986, figure 3). The rectangle indicates the approximate position and exposure level of the Glen Ey Gorge GCR site.

(Figure 6.10) Map of the area around the Cairn Leuchan to Pannanich Hill GCR site, adapted from the BGS 1:50 000 Sheet 65E (Ballater, 1995). The Coyles of Muick Intrusion is bounded on both sides by ductile shears that define the Coyles of Muick Shear-zone. The shear-zone also marks the position of the regional andalusite–kyanite isograd; to the north-west metasedimentary rocks contain andalusite ± staurolite (a Buchan-type assemblage), whereas to the south-east they contain the assemblage sillimanite ± kyanite ± staurolite, characteristic of Barrovian metamorphism.

(Figure 6.11) Map of the area around Balnacraig, Dinnet. Modified after Gould (2001, figure 11)

(Figure 6.12) Xenolithic gneiss with folded remnants of psammite dispersed in poorly foliated feldspar-porphyroblast gneiss. Craigie, 1.5 km north-east of Dinnet [NJ 476 007]. Coin is 26 mm in diameter. (Photo: BGS No. P220491, reproduced with the permission of the Director, British Geological Survey, © NERC.)

(Figure 6.13) Amphibolite, with irregular patches of feldspathic material, Balnacraig Cottage, north-east of Dinnet [NJ 4787 0056]. Coin is 25 mm in diameter. (Photo: BGS No. P 220371, reproduced with the permission of the Director, British Geological Survey, © NERC.)

(Figure 6.14) Map of the Muckle Fergie Burn section, Glen Avon, based upon British Geological Survey mapping, 1982–88.

(Figure 6.15) Granitic cobbles, typically up to 10 cm across, in metadiamictite in the lower part of the Muckle Fergie Burn [NJ 1657 1397]. The smaller clasts include granite, quartz and ochreous yellow-brown-weathering metadolostone (see example at bottom right). (Photo: J R Mendum, BGS No. P 726597)

(Figure 6.16) Map of the area around Bridge of Brown, based upon BGS 1:10 000 Sheet NJ12SW (1991). The line of part of the cross-section in (Figure 6.17) is indicated.

(Figure 6.17) North-west–south-east cross-section across the area surrounding the Bridge of Brown and Bridge of Avon GCR sites. The line of section intersects (Figure 6.16) and passes to the south-west of (Figure 6.18).

(Figure 6.18) Map of the area around the Bridge of Avon, based upon BGS 1:10 000 sheets NJ12SW (1991) and NJ12SE (1992) and on BGS 1:50 000 Sheet 75W (Glenlivet, 1996). The cross-section of (Figure 6.17) passes the south-west corner of this map.

(Figure 6.19) Asymmetrical minor F3 folds of thinly interbedded metalimestone, calcsilicate rock and calcareous semipelite of the Ailnack Phyllite and Limestone Formation at Bridge of Avon [NJ 150 201]. The folds show attenuated limbs and fold axes plunge at 25° to 152°. (Photo: BGS No. P 220186, reproduced with the permission of the Director, British Geological Survey, © NERC.)

(Figure 6.20)

(a) Map of the Kymah Burn section, Glen Livet, based upon British Geological Survey mapping, 1982–88.

(b) Cross-section along the line A–B showing the major fold interference structure in the Kymah Burn section.

(Figure 6.21) Map of the section through metavolcanic rocks in the lower part of the Blackwater Formation, exposed in the Black Water. Adapted from the BGS 1:10 000 Sheet NJ33SE (1993).

(Figure 6.22) A typical fragmental ultrabasic volcanic rock from the Kelman Hill Member of the Blackwater Formation. The dominant, pale, subrounded to subangular clasts are derived from picritic lavas and there are smaller, darker and more-rounded clasts that are probably from metabasalts. Loose block near Shenval, Black Water GCR site [NJ 363 308]. Coin is 20 mm diameter. (from Macdonald et al., 2005, figure 4.) (Photo: BGS No. P 582442, reproduced with the permission of the Director, British Geological Survey, © NERC.)

(Figure 6.23) Map of the area around Auchindoun Castle, Glen Fiddich from BGS 1:10 000 sheets NJ33NW (1993) and NJ33NE (1993). The Portsoy Lineament lies some 4.5 km to the south-east of the castle. Most of the exposures of pelites in this area show square cross-sections of chiastolite in hand specimen and thin sections reveal that this has been replaced by kyanite (Figure 6.24).

(Figure 6.24) Chiastolite (=andalusite) porphyroblasts pseudomorphed by fan-like sheaves of kyanite in a sample of pelite from the Mortlach Graphitic Schist Formation close to Auchindoun Castle. The original ‘crosses’ formed by graphite inclusions in the chiastolite are still clearly visible. (from Beddoe-Stephens, 1990, figure 2a). (Photo: BGS No. P 254543, reproduced with the permission of the Director, British Geological Survey, © NERC.)

(Figure 6.25) Map of the coastal strip between Cullen and Troup Head, based largely upon BGS 1:50 000 sheets 96W (Portsoy, 2002) and 96E (Banff, 2002). Late-Caledonian minor intrusions are omitted for clarity.

(Figure 6.26) Cross-section of the coast between Cullen and Troup Head, based largely upon sections accompanying BGS 1:50 000 sheets 96W (Portsoy, 2002) and 96E (Banff, 2002). Key as in (Figure 6.25).

(Figure 6.27) Ripples on bedding surface in the Findlater Castle Quartzite at Findlater Castle. (Photo: BGS No. P 008614, reproduced with the permission of the Director, British Geological Survey, © NERC.)

(Figure 6.28) View westwards from Portsoy Old Harbour towards Redhythe Point. The rocks of the near and middle distance are mostly highly deformed semipelites, quartzites, metalimestones and graphitic pelites within the Portsoy Shear-zone; note the very strong, steeply plunging lineation in the quartzite on the left. The second promontory away from the camera consists of serpentinized peridotite, worked and sold locally as ‘Portsoy Marble’. (Photo: J.R. Mendum, BGS No. P 001134.)

(Figure 6.29) Andalusite porphyroblasts in the semipelitic part of the Knock Head Grit Member of the Macduff Slate Formation at Boyndie Bay. The hammer shaft is 35 cm long. (Photo: BGS No. P 221160, reproduced with the permission of the Director, British Geological Survey, © NERC.)

(Figure 6.30) Quartzofeldspathic boulder, interpreted as a dropstone from a floating iceberg in the Macduff ‘Boulder Bed’, Macduff Slate Formation, The Sclates, Macduff. Professor Janet Watson provides a scale. (Photo: J.R. Mendum, BGS No. P 726598.)

(Figure 6.31) Map of the coast section between Fraserburgh and Rosehearty, based upon the BGS 1:50 000 Sheet 97 (Fraserburgh, 1987). The diagrammatic cross-section is adapted from Loudon (1963) and is not to scale.

(Figure 6.32) Refolded folds (F1 + F3) in a mixed sequence of thinly bedded calcareous semipelites, calcsilicate rocks and impure metalimestones of the Kinnaird’s Head Formation at Kinnaird’s Head, Fraserburgh.

(a) Tight F1 folds refolded by close to tight F3 folds, immediately east of the foghorn at [NJ 998 677]. A prominent S3 axial-planar cleavage and an L3 lineation are well developed in places. Hammer head is 16.5 cm long. (Photo: J.R. Mendum, BGS No. P 726599.)

(b) Refolded folds (F1 + F3), viewed to the east, at [NJ 998 676]. Key fob is 4 cm in diameter. (Photo: D.J. Fettes, BGS No. P 726600.)

(Figure 6.33) Cyclic bedding with graded units in the Rosehearty Formation. Andalusite is abundant in the finer-grained units. Note the cross-cutting cleavage. West of Sandhaven, [NJ 952 679]. Key fob is 4 cm in diameter. (Photo: D.J. Fettes, BGS No. P 726601.)

(Figure 6.34) Graded units with thin sandstone layers in a dominantly pelitic facies of the Rosehearty Formation. Abundant andalusite is clearly visible. Location as (Figure 6.33). Pen is 15 cm long. (Photo: D.J. Fettes, BGS No. P 726602.)

(Figure 6.35)

(a) Map of the Cairnbulg to St Combs coast section showing the textural varieties of migmatitic rocks within the Inzie Head Gneiss Formation. Modified after Johnson et al. (2001b). See text for explanations of the terminology.

(b) Map summarizing mineralogical characteristics of the leucosome element of the gneisses.

(Figure 6.36) Schematic crustal section prior to D4 folding and uplift, showing the nature of migmatitic rocks in the Inzie Head Gneiss Formation and their relationships with the mid-Ordovician mafic and felsic intrusions. From Johnson et al. (2001b).

(Figure 6.37) Cairnbulg Granite intruded into diktyonitic metatexite and nebulitic diatexite with relict metasedimentary schollen of the Inzie Head Gneiss Formation. Top of beach, south of Cairnbulg Harbour. The hammer shaft is 35 cm long. (Photo: J.R. Mendum, BGS No. P 726603.)

(Figure 6.38) Schollen diatexites (L-gt zone), with large garnets now mainly retrogressed to chlorite in the Inzie Head Gneiss Formation. The calcsilicate lenses and psammites form metasedimentary schollen. The rocks were derived by anatectic partial melting of the dominantly semipelitic rocks. Point of Whitelinks, east of Inverallochy, Cairnbulg to St Combs GCR site. The hammer shaft is 35 cm long. (Photo: J.R. Mendum, BGS No. P 726604.)

(Figure 6.39) Map of the Collieston to Whinnyfold coast section showing D1 and D3 structural elements, adapted from Mendum (1987). The inset equal-area stereographic projection shows structural elements of the section between Whinnyfold and Old Castle.

(Figure 6.40) Composite cross-section of the coast section between Collieston and Whinnyfold, showing the overall fold pattern in a plane normal to the fold axes. From Mendum (1987).

(Figure 6.41) An excellent example of a recumbent, east-facing F1 fold in dominantly inverted gritty psammites of the Collieston Formation, viewed towards the north-north-east. Devil’s Study, Collieston to Whinnyfold coast section. J.R. Mendum provides a scale. (Photo: BGS No. P 002878, reproduced with the permission of the Director, British Geological Survey, © NERC.)

(Figure 7.1) Map of the Shetland Islands showing the outcrops of the Moine and Dalradian ‘divisions’ and overlying structural units. From Flinn et al. (1972) with modifications taken from the BGS 1:50 0000 sheet 131 (Unst and Fetlar, 2002).

Proposed GCR sites: 1 Scalloway, 2 Hawks Ness, 3 Cunningsburgh.

BSF Bluemull Sound Fault, NF Nesting Fault, WBF Walls Boundary Fault.

(Figure 7.2) Map of the ‘divisions’ of Moine and Dalradian rocks on Mainland Shetland, east of the Walls Boundary Fault (the so-called ‘East Mainland Succession’), showing main structural features and the location of the proposed GCR sites: 1 Scalloway, 2 Hawks Ness, 3 Cunningsburgh.

BSF Bluemull Sound Fault, NF Nesting Fault, WBF Walls Boundary Fault.

(Figure 7.3) Schematic cross-section of the East Mainland Mega-monocline and Valla Field Anticline, Shetland (after Flinn, 2007).

EMM East Mainland Mega-monocline axial plane trace.

(Figure 7.4) Map of the area around the Scalloway GCR site.

(Figure 7.5) Typical homogeneous granoblastic gneiss of the Colla Firth Permeation Belt, Whiteness Group, viewed normal to the lineation and parallel to the foliation. Point of the Pund, Scalloway [HU 3873 3889]. Hammer shaft is 33 cm long. (Photo: D. Flinn, BGS No. P 574422.)

(Figure 7.6) Map of the area around the Hawks Ness GCR site. Inset is an equal-area stereographic projection showing the relationship between poles to bedding, axes of prominent isoclinal folds in individual quartzite beds and fabric lineations.

(Figure 7.7) Ripple cross-lamination preserved within the Dales Voe Grit Member of the Clift Hills Phyllitic Formation. Brim Ness [HU 4606 4825]. Hammer head is 16.5 cm long. (Photo: F. May, BGS No. P 726605.)

(Figure 7.8) Structures in the Clift Hills Phyllitic Formation (see stereoplot inset in (Figure 7.6)).

(a) Isoclinal synform in beds of turbiditic psammite of the Dales Voe Grit Member. Houbie [HU 4572 4807].

(b) South-west-plunging lineation caused by tectonic elongation of clastic grains in a bed of coarse, schistose psammite. North-west tip of Hawks Ness [HU 4583 4909]. Coin is 30 mm diameter.

(Photos: F. May, BGS Nos. P 726606 and P 726607.)

(Figure 7.9) Map of the area around the Cunningsburgh GCR site.

(Figure 7.10) Spinifex-like texture preserved as pseudomorphs after olivine in a block of brecciated and then serpentinized ultramafic rock. Hillside south-west of Sands of Mail, Cunningsburgh [HU 4261 2744]. Coin is 26 mm in diameter. (Photo: D. Flinn, BGS No. P 550134.)

(Figure 7.11) Tectonically stretched clasts within a debris-flow deposit, probably volcaniclastic, interbedded with spilitic lavas of the Dunrossness Spilitic Formation on the coast south-west of Mail, Cunningsburgh [HU 429 278]. Hammer shaft is 28 cm long. (Photo: P. Stone, BGS No. P 726608.)

Figure G.1 Simplified examples of the use of the equal-area stereographic projection (lower hemisphere) to represent geological structures:

(a) representation of a bedding plane as a great-circle trace and as a pole.

(b) representation of a fold hinge line (fold axis) as a point, lying on the axial plane (great circle).

(c) example of a point distribution, defined by poles to gently dipping beds, mean dip = 05°.

(d) example of a girdle distribution of poles to bedding, with a best-fit great circle, and its pole (fold axis).

Figure G.2 Diagram to illustrate the concept of ‘facing’ direction of folds, introduced by Shackleton (1958) as a means to describe the structural ‘way-up’ of strata. Shackleton defined ‘facing’ geometrically as ‘the direction normal to the fold axis, along the axial plane, and towards the younger beds’. Thus a synclinal synform is described as ‘upward facing’, whereas an anticlinal (i.e. inverted) synform is ‘downward facing’. Asymmetrical and recumbent folds have a sideways component of facing which is an important descriptive parameter, and which has commonly been used to infer the direction of tectonic transport.

Figure G.3 Fold terminology:

(a) single inclined fold pair illustrating the basic fold nomenclature (from McClay, 1987);

(b) fold train showing the change from upright to recumbent fold and the concept of an enveloping surface (from McClay, 1987);

(c) terms to describe the tightness of folds (from McClay, 1987);

(d) Asymmetrical minor folds showing Z, S and M symmetry and their typical relationship to larger scale antiformal and synformal structures (from McClay, 1987);

(e) Fold profile showing direction of vergence of an asymmetrical fold (from Bell, 1981);

(f) Geometry of coaxially refolded folds showing F1 and F2 major folds and related minor fold structures. Note how minor F1 folds change vergence across F1 fold axial traces but maintain a consistent vergence across the F2 fold axial traces, whilst changing their facing from upwards to downwards. Minor F2 folds change their vergence across the F2 axes (after Bell, 1981);

(g) Geometry of orthogonally refolded folds. Note that both F1 and F2 folds change vergence across F2 fold axes but not facing direction (arrows indicate facing direction of F1 folds) (after Bell, 1981).

Figure G.4 Pressure/Depth–Temperature diagram showing the fields of metamorphic facies (Yardley, 1989) Abbreviations: a-e–albite-epidote, hbl–hornblende, hfls–hornfels, preh-pump–prehnite-pumpellyite, px–pyroxene.

Table 1.1 (In text) Dalradian rocks of Scotland: GCR networks and site selection criteria.

Table 2.1 (In text) Stratigraphical sequences for the lower part of the Colonsay Group according to Stewart and Hackman (1973) and Muir et al. (1995).

Table 3.1 (In text) Summary of the Dalradian sequence in the Schiehallion district (adapted from Treagus, 2000).

* the Atholl and Strathtummel subgroups of Treagus (2000) are no longer recognized; the strata are now regarded as part of the Glen Spean Subgroup.

(Table 7.1) The East Mainland Succession of Shetland, showing tentative informal correlations with the Moine and Dalradian supergroups of mainland Scotland. Stratigraphical ranges exhibited by the GCR sites are also shown: 1 Scalloway, 2 Hawks Ness, 3 Cunningsburgh.

(Front cover) Medium-scale folds with fanned spaced cleavages, related to the major early (F1) Kilmory Bay Syncline and developed in the basal part of the Crinan Grit Formation at the Kilmory Bay GCR site, Knapdale. The folding is controlled by a single competent bed of fine-grained quartzite within incompetent metamudstones that exhibit chlorite-grade, greenschist-facies regional metamorphism. Most of the GCR sites in this volume are important as representatives of key parts of the Dalradian succession, for their characteristic lithologies and for the regional metamorphism and spectacular structures imposed upon them during the Caledonian Orogeny. Some have historical value, and it was here that graded bedding was first used, in 1911, to demonstrate the way-up of deformed strata in the Scottish Highlands. (Photo: P.W.G. Tanner.)

References