Smith, R.A., Merritt, J.W., Leslie, A.G., Krabbendam, M., and Stephenson, D. 2011. Bedrock and Superficial Geology of the Newtonmore–Ben Macdui district: Description or Sheet 64 (Scotland). British Geological Survey Internal Report, OR/11/055. Download PDF

Figures, plates and tables

Figures

(Figure 1) Outline Bedrock Geology of the Newtonmore–Ben Macdui district (Sheet 64W & E)

(Figure 2) Simplified geological map of the Glen Banchor Subgroup outcrop

(Figure 3) Distribution of Appin and Argyll groups on Sheet 64E without the Siluro-Devonian intrusions and minor faults.

(Figure 4) Distribution of internal components within the Cairngorm Pluton (Modified after Harrison, 1986).

(Figure 5) Simplified geological map of Gaick region (Sheet 64W) showing the system of north-south trending F2 fold axial traces detected. The section line X-X’ is the line of section on Figure 6. The inset map shows the general location as a black rectangle (taken from Leslie et al. 2006).

(Figure 6) (a): Transect of the Gaick Fold Complex for the section line X–X’ on Figure 5. (b): Schematic cross-section from the Geal Charn-Ossian Steep Belt in the north to the Tay Nappe Flat Belt in the south (taken from Leslie et al., 2006).

(Figure 7) Major structures in the southern part of Sheet 64E (Ben Macdui), with emphasis on the Appin and Argyll Group Dalradian.

(Figure 8) Hillshaded Digital Elevation Model of the district.

(Figure 9) Hillshaded Digital Elevation Model of the southern end of the Lairig Ghru in the Cairngorms showing glacial features and a reconstruction of ice flow at the Late Glacial Maximum (LGM).

(Figure 10) Hillshaded Digital Elevation Model of Glen Truim and Strathspey showing glacial features, a reconstruction of ice flow at the LGM and inferred recessional stages.

(Figure 11) British Quaternary chronostratigraphy (after Gordon, 1997; Bowen et al., 1999) and a representative oxygen isotope and geomagnetic polarity record (ODP 677) (after Shackleton et al., 1990; Bowen et al., 1999).

(Figure 12) Reconstruction of flowlines and ice divides within the Main Late Devensian ice sheet following the Last Glacial Maximum (LGM). Some West Grampian-Strathspey ice probably flowed eastwards into the valley of the Geldie Water at the maximum build-up of ice.

(Figure 13) Reconstruction of the pattern of ice recession. Thick line denotes approximate boundary between West Grampian-Strathspey ice and ice sourced over the Cairngorms and Gaick at the LGM.

(Figure 14) Limits of glacial readvances following the LGM and including the Loch Lomond Readvance.

(Figure 15) Thermomechanical ice sheet model for the Loch Lomond Readvance (after Golledge et al., 2008).

(Figure 16) Distribution of subgroups of the Caledonian Glacigenic Group. (Reproduced with the kind permission of D. Jarman)

(Figure 17) Hillshaded Digital Elevation Model of ice-marginal channels in the valley of the Allt an Dubh-chadha showing inferred ice recessional stages and reconstruction of ice flow at the LGM.

Plates

(Plate 1) Photomicrograph of a micaceous psammite from Allt a' Chaorainn, Glen Banchor, two miles north- west of Newtonmore showing brown biotite mica flakes and a garnet (centre) within a pale quartzo- feldspathic groundmass. BGS Petrology sample no. S99651. BGS Imagebase No. P515219

(Plate 2) Photomicrograph of a sheared semipelite from Creag an Loin, two miles north-west of Newtonmore containing grey fibrolite foliae parallel to aligned laths of brown biotite in a fine-grained quartzo-feldpathic matrix. BGS Petrology sample no. S99663. BGS Imagebase No. P515224

(Plate 3) Right-way-up cross-bedding in Gaick Psammite beside Allt Bhran [NN 7707 8971] BGS Imagebase No. P514826.

(Plate 4) Crags with dominant planar foliation in psammite and micaceous psammite, Gaick Psammite Formation in Allt Gharbh Ghaig, Gaick [NN 78847 81847] BGS Imagebase No. P521713.

(Plate 5) Folded metalimestone and semipelite in the Forest Lodge Member, Glen Banvie Formation above the ruined Dail-an-eas Bridge, Glen Tilt [NN 9387 7466]. BGS Imagebase No. P663222.

(Plate 6) Interbanded graphitic semipelite and fine-grained quartzite typical of the Beinn a’ Ghlo Transition Formation. Allt an Lochain at about NN 986 772. BGS Imagebase No. P922402.

(Plate 7) Multiple cross-bed sets younging towards the top of the photograph in An Socach Quartzite Formation on Carn an Righ [NO 0219 7689]. BGS Imagebase No. P258111.

(Plate 8) Crag of layered metalimestone and semipelite (‘tiger rock’) on purer metalimestone within the Glen Loch Phyllite and Limestone Formation, looking north-east up Glen Tilt at about NN 977 779. BGS Imagebase No. P922403.

(Plate 9) Domino-style boudinage and extension structures in metacarbonate rocks of the Gleann Mor Limestone Member in Gleann Mor [NO 0137 7634]. BGS Imagebase No. P258112.

(Plate 10) Boudinaged, folded grey pelitic layers in metalimestone. Sron an Dias Pelite and Limestone Formation on Sron an Dias [NN 9935 7295]. BGS Imagebase No. P922404.

(Plate 11) Laminated garnet-poor metasiltstones of the Tulaichean Schist Formation, near the watershed on the Carn an t-Sionnaich - Faire a’ Ghlinne Mhoir ridge [NO 0246 7513]. BGS Imagebase No. P258113.

(Plate 12) Very large pink garnet porphyroblasts weathering out of muscovite-biotite-amphibole schist within the Tulaichean Schist Formation near the top of Meall Reamhar [NN 993 759]. BGS Imagebase No. P922405.

(Plate 13) Weathered boulders of Main Phase Granite, part of the Cairngorm Pluton as exposed on Derry Cairngorm [NO 0173 9803] looking west to Lochan Uaine and Ben Macdui in the background. BGS Imagebase No. P51430.

(Plate 14) Pink granite veins of the Glen Tilt Pluton intruding Glen Banvie Formation below the ruined Dail- an-eas Bridge, River Tilt [NN 9385 7465]. BGS Imagebase No. P663227.

(Plate 15) A transecting S2 fabric on S0 bedding in the Gaick Psammite Formation, An Dun, Gaick [NN 71895 80823]. BGS Imagebase No. P521694.

(Plate 16) The Creag an Lochan Duin fold. Photomontage of fold profile in Gaick Psammite Formation at An Dun/Creag an Loch, Gaick [NN 72007 81311]. BGS Imagebase No. P5217000.

(Plate 17) South-east-facing (to the right) in a F2 minor fold hinge affecting sedimentary cross-lamination in Gaick Psammite Formation. Cross-lamination oversteepened in the hinge-zone above the compass. Allt Bhran [NN 76559 90129]. BGS Imagebase No. P514833.

(Plate 18) Major fold hinge (?F2), plunging towards the viewer in crag on the right, within metalimestones of the Glen Loch Phyllite and Limestone Formation, looking east up a small burn north of Creag an Duibh, taken from Glen Tilt at about NN 983 791. BGS Imagebase No. P922763.

(Plate 19) Major linear gully along the line of the Loch Tay Fault exploited by the River Tilt with the Beinn a’ Ghlo range in the background. Looking south-west down Glen Tilt from Creag an Duibh [NN 986 791]. BGS Imagebase P601615.

(Plate 20) A 30 m-wide cataclastic zone in Gaick Psammite exposed in Allt a’ hama Choire at [NN 7050 7962]. BGS Imagebase No. P514843.

(Plate 21) The central breach through the Gaick plateau looking NNE through the Loch an Dùin Gap. Valley of the Edendon Water in the foreground. Cairngorms in the distance to the left. BGS Imagebase No. P239928.

(Plate 22) The peat-covered Gaick plateau looking west towards A’ Bhuidheanach Bheag. BGS Imagebase No. P543641.

(Plate 23) Creagan a’ Choin [NN 703 957], a large roche moutonnée feature in the Spey Valley south of Newtonmore. Ice flowed from right to left, north-eastwards. BGS Imagebase No. P543686.

(Plate 24) Recessional moraine ridges and associated ice-marginal glacial meltwater channels in the valley of the Tarf Water looking north-east towards the head-covered slopes of Sron na Macranaich [NN 937 818]. BGS Imagebase No. P536161.

(Plate 25) Cross bedded gravel within the Ceardaich Sand and Gravel Formation at river cliff section ME 226 [NN 7937 7362] in the valley of the Allt a’ Chireachain. BGS Imagebase No. P543664.

(Plate 26) Fine-grained, cross-stratified sand of the Ceardaich Sand and Gravel Formation overlain by diamicton of the Ardverikie Till Formation at section ME 225 [NN7960 7374] in the valley of the Allt a’ Chireachain. The uppermost 0.5 m of the sand unit is pervasively sheared parallel to the planar base of the overlying till. Beds dip toward the SW. BGS Imagebase No. P543665.

(Plate 27) Trackside section ME 293 [NN 6824 9887] in extremely poorly sorted, stratified, matrix-supported diamicton with laterally discontinuous beds of laminated sand and silt. Deposit was probably formed at the receding ice margin by debris flow and sheet wash processes. BGS Imagebase No. P543683.

(Plate 28) Subglacial till with a matrix of silty fine-grained sand exposed in a deep gully of the Ruighe Bad an Fheidh, southern Gaick. BGS Imagebase No. P543675.

(Plate 29) River cliff section ME 275b [NN 6844 8711] on the northern bank of the Allt Cuaich, revealing a boudinaged lens of sand within diamicton interpreted as deformation till with shearing towards the NE. BGS Imagebase No. P543708.

(Plate 30) Recessional moraine ridges and associated ice-marginal glacial meltwater channels in the valley of the Bruar Water [NN 8283 7700], looking north-north-east. Ice retreated towards the left. BGS Imagebase No. P543857.

(Plate 31) Roadside section ME 291 [NN 6982 9659] in loose, very poorly sorted, silty sand and gravel forming moundy morainic deposits to the south of Newtonmore. BGS Imagebase No. P543687.

(Plate 32) Recessional moraines in Glen Loch, looking north-north-east. BGS Imagebase No. P772049.

(Plate 33) Roadside section ME 292 [NN 6903 9503] in dense, very poorly sorted, clast-supported cobble gravel forming a glaciofluvial terrace in the valley of the River Truim. BGS Imagebase No. P543685.

(Plate 34) Glacitectonised laminated silts and clays underlying till at the top of section ME 207 in Coire Mhic- sith [NN 658 745]. BGS Imagebase No. P551775.

(Plate 35) Close-up of folded and faulted laminated silts and clays towards the top of the unit shown in previous figure. The sense of thrusting is toward the east (right) in this image. BGS Imagebase No. P551773.

(Plate 36) A stone lobe on the southern flank of Sròn na Faiceachan [NN 8182 7635]. BGS Imagebase No. P543657.

(Plate 37) Blockfield developed on pink biotite-granite on the main summit of Beinn Dearg [NN 853 778]. BGS Imagebase No. P543669.

(Plate 38) Talus cones in the Lairig Ghru in the vicinity of the Pools of Dee. BGS Imagebase No. P536315.

(Plate 39) Tension cracks and antiscarp benches on the steep slopes of A’ Chaoirnich in the Gaick Pass.

Tables

(Table 1) Relationships of the subgroups, formations and members of the Grampian Group present on Sheet 64

(Table 2) Stratigraphical jargon-buster for the Glen Spean Subgroup in the Strathtummel Basin (adapted from Banks et al., 2006; 2007)

(Table 3) Relationships of the formations in the Appin and Argyll groups of the Dalradian Supergroup on Sheet 64

(Table 4) Lithostratigraphy of some glacigenic deposits in the district.

(Front cover)James Hutton’s Locality above Dail-an-Eas Bridge [NN 9388 7467], looking north-east up Glen Tilt whose trend is largely controlled by the Loch Tay Fault. Here Hutton observed granite veins cutting and recrystallising Dalradian metasedimentary rocks and deduced that granite crystallised from a hot liquid. BGS Imagebase P601616.

References

(Figure 1) Outline Bedrock Geology of the Newtonmore–Ben Macdui district (Sheet 64W & E)

(Figure 2) Simplified geological map of the Glen Banchor Subgroup outcrop

(Figure 3) Distribution of Appin and Argyll groups on Sheet 64E without the Siluro-Devonian intrusions and minor faults.

(Figure 4) Distribution of internal components within the Cairngorm Pluton (Modified after Harrison, 1986).

(Figure 7) Major structures in the southern part of Sheet 64E (Ben Macdui), with emphasis on the Appin and Argyll Group Dalradian.

(Figure 8) Hillshaded Digital Elevation Model of the district.

(Figure 9) Hillshaded Digital Elevation Model of the southern end of the Lairig Ghru in the Cairngorms showing glacial features and a reconstruction of ice flow at the Late Glacial Maximum (LGM).

(Figure 10) Hillshaded Digital Elevation Model of Glen Truim and Strathspey showing glacial features, a reconstruction of ice flow at the LGM and inferred recessional stages.

(Figure 13) Reconstruction of the pattern of ice recession. Thick line denotes approximate boundary between West Grampian-Strathspey ice and ice sourced over the Cairngorms and Gaick at the LGM.

(Figure 14) Limits of glacial readvances following the LGM and including the Loch Lomond Readvance.

(Figure 15) Thermomechanical ice sheet model for the Loch Lomond Readvance (after Golledge et al., 2008).

(Figure 16) Distribution of subgroups of the Caledonian Glacigenic Group. (Reproduced with the kind permission of D. Jarman).

(Figure 17) Hillshaded Digital Elevation Model of ice-marginal channels in the valley of the Allt an Dubh-chadha showing inferred ice recessional stages and reconstruction of ice flow at the LGM.

(Plate 3) Right-way-up cross-bedding in Gaick Psammite beside Allt Bhran [NN 7707 8971] BGS Imagebase No. P514826.

(Plate 4) Crags with dominant planar foliation in psammite and micaceous psammite, Gaick Psammite Formation in Allt Gharbh Ghaig, Gaick [NN 78847 81847] BGS Imagebase No. P521713.

(Plate 5) Folded metalimestone and semipelite in the Forest Lodge Member, Glen Banvie Formation above the ruined Dail-an-eas Bridge, Glen Tilt [NN 9387 7466]. BGS Imagebase No. P663222.

(Plate 6) Interbanded graphitic semipelite and fine-grained quartzite typical of the Beinn a’ Ghlo Transition Formation. Allt an Lochain at about NN 986 772. BGS Imagebase No. P922402.

(Plate 7) Multiple cross-bed sets younging towards the top of the photograph in An Socach Quartzite Formation on Carn an Righ [NO 0219 7689]. BGS Imagebase No. P258111.

(Plate 9) Domino-style boudinage and extension structures in metacarbonate rocks of the Gleann Mor Limestone Member in Gleann Mor [NO 0137 7634]. BGS Imagebase No. P258112.

(Plate 10) Boudinaged, folded grey pelitic layers in metalimestone. Sron an Dias Pelite and Limestone Formation on Sron an Dias [NN 9935 7295]. BGS Imagebase No. P922404.

(Plate 14) Pink granite veins of the Glen Tilt Pluton intruding Glen Banvie Formation below the ruined Dail- an-eas Bridge, River Tilt [NN 9385 7465]. BGS Imagebase No. P663227.

(Plate 15) A transecting S2 fabric on S0 bedding in the Gaick Psammite Formation, An Dun, Gaick [NN 71895 80823]. BGS Imagebase No. P521694.

(Plate 16) The Creag an Lochan Duin fold. Photomontage of fold profile in Gaick Psammite Formation at An Dun/Creag an Loch, Gaick [NN 72007 81311]. BGS Imagebase No. P5217000.

(Plate 20) A 30 m-wide cataclastic zone in Gaick Psammite exposed in Allt a’ hama Choire at [NN 7050 7962]. BGS Imagebase No. P514843.

(Plate 22) The peat-covered Gaick plateau looking west towards A’ Bhuidheanach Bheag. BGS Imagebase No. P543641.

(Plate 23) Creagan a’ Choin [NN 703 957], a large roche moutonnée feature in the Spey Valley south of Newtonmore. Ice flowed from right to left, north-eastwards. BGS Imagebase No. P543686.

(Plate 25) Cross bedded gravel within the Ceardaich Sand and Gravel Formation at river cliff section ME 226 [NN 7937 7362] in the valley of the Allt a’ Chireachain. BGS Imagebase No. P543664.

(Plate 28) Subglacial till with a matrix of silty fine-grained sand exposed in a deep gully of the Ruighe Bad an Fheidh, southern Gaick. BGS Imagebase No. P543675.

(Plate 31) Roadside section ME 291 [NN 6982 9659] in loose, very poorly sorted, silty sand and gravel forming moundy morainic deposits to the south of Newtonmore. BGS Imagebase No. P543687.

(Plate 32) Recessional moraines in Glen Loch, looking north-north-east. BGS Imagebase No. P772049.

(Plate 34) Glacitectonised laminated silts and clays underlying till at the top of section ME 207 in Coire Mhic- sith [NN 658 745]. BGS Imagebase No. P551775.

(Plate 36) A stone lobe on the southern flank of Sròn na Faiceachan [NN 8182 7635]. BGS Imagebase No. P543657.

(Plate 37) Blockfield developed on pink biotite-granite on the main summit of Beinn Dearg [NN 853 778]. BGS Imagebase No. P543669.

(Plate 38) Talus cones in the Lairig Ghru in the vicinity of the Pools of Dee. BGS Imagebase No. P536315.

(Plate 39) Tension cracks and antiscarp benches on the steep slopes of A’ Chaoirnich in the Gaick Pass.

(Table 1) Relationships of the subgroups, formations and members of the Grampian Group present on Sheet 64

(Table 2) Stratigraphical jargon-buster for the Glen Spean Subgroup in the Strathtummel Basin (adapted from Banks et al., 2006; 2007)

(Table 3) Relationships of the formations in the Appin and Argyll groups of the Dalradian Supergroup on Sheet 64

(Table 4) Lithostratigraphy of some glacigenic deposits in the district.

(Front cover) James Hutton’s Locality above Dail-an-Eas Bridge [NN 9388 7467], looking north-east up Glen Tilt whose trend is largely controlled by the Loch Tay Fault. Here Hutton observed granite veins cutting and recrystallising Dalradian metasedimentary rocks and deduced that granite crystallised from a hot liquid. BGS Imagebase P601616.