Field Trip to Scotland
Saturday 2nd - Sunday 10th August, 1997
By David Hill
By David Hill
Three members of the Hull Geological Society and their families went on this trip in two camper-vans with the aim of seeing as much of the varied geology of Scotland as possible.
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Saturday 2nd August was spent in the SW of Scotland where we visited 5 sites.
Clatteringshaws Dam Quarry for pegmatite and garnet.
(BGS Geology in SW Scotland p 148-9, Gem & Mineral Sites of S Scotland, OS Sheet 77, NX 547 754).
The quarry is in the outer facies of the Cairnsrnore of Fleet granite pluton and is composed mainly of a coarse-grained grey granite. In places we found pegmatite and aplite veins and extracted small pieces of albite feldspar and biotite mica. The east side of the quarry is composed of reddish granite and we had difficulty understanding how such dissimilar material originated from the same magma.
Near Pinwherry to look for blue-schist.
(Geol. Exc. around Glasgow & Girvan p346, OS Sheet 76, NX 1375 8890).
This location is above the coastal plain and there is little in the way of outcrops. We investigated the stream beside the road just north of the cattle grid and found quite a variety of weathered serpentinite minerals and some bluish slatey material which was the closest to blue-schist.
Bonney's Dyke, a gabbro pegmatite.
(Geol. Exc. around Glasgow & Girvan p338, OS Sheet 76, NX 1347 9113).
Bonney's Dyke is actually a steeply dipping sill of gabbro pegmatite, rather than a
dyke, intruded into serpentinite. It is composed of a white altered feldspar and black pyroxene. The altered serpentinite to the south of the sill contains large crystals of the
green pyroxene diallage pieces of which were easy to obtain from beach boulders.
Pinbain Bridge for chromite in serpentinite.
(BGS Classic areas of British Geology – Ballentrae p32, OS Sheet 76, NX 1386 9152).
On the opposite side of the road from the sea is the raised sea cliff just north of Pinbain Bridge which here consists of a small inlet with a sea stack and a cliff face made almost entirely of serpentinite with the deposit of chromite near the top at the back.
Lady Burn for Ordovician fossils.
(Geol. Exc. around Glasgow & Girvan p425, OS Sheet 76, 250 036).
It was necessary to ask permission at South Threave Farm to visit Lady Burn. The site is world famous and collecting is restricted. There are a number of opencuts and trenches made by fossil collectors and a large amount of material on dumps. The rock is a brown-weathering blue mudstone with most fossils preserved as moulds. Due to the restrictions we spent our time examining the material in the dumps. We found examples of Calvmene drummuckensis and other trilobites as well as brachiopods, gastropods and bivalves. Also a part of a starfish was found.
Sunday 3rd August, we started in Ayreshire and proceeded up the West side of Scotland.
Loanhead basalt quarry.
(Geol. Exc. around Glasgow & Girvan p239, OS Sheet 63, NS 365 555).
This quarry is worked for roadstone and there are minerals in vesicles in the basalt.
As it is a working quarry we had to wear hard hats and obtain permission to enter. We found nice samples of prehnite as well as calcite crystals and bits of analcite and malachite.
Tyndrum lead/zinc mine.
(Gemstone Sites of the British Isles, OS Sheet 50, 320 305).
Tyndrulm is a small town and a hill on the west of the town contains the mine which appears to be just one large scree slope. The mineral deposit runs vertically through the hill and was accessed at several levels, many of the lower adits now being buried by the waste from upper levels. There is a lot of the zinc ore sphalerite on the dumps, but good crystals are rare. Near the top is a reasonably safe access into the upper part of the mine workings where we could see galena, sphalerite and pyrite in situ.
Glen Coe to look for banded rhyolite.
There are two small quarries in the rhyolite at the head of Glen Coe Much of the rhyolite is featureless but we found nice samples of both grey and pink banded rhyolite.
Ballachulish Slate Quarry which has pyrite cubes in the slate.
(GS Summary of mineral resources of the 'Crofter Counties' of Scotland)
We looked round the visitors' centre which has a good display about the slate industry in Scotland and details about how the quarry and dumps were restored. Sheer faces have been left for use by rock climbers, scree slopes for geologists, lakes for fishing and grass and wooded areas for picnicking. We had a look at the slate which is cut by veins of white quartz and collected some samples of slate with pyrite cubes.
Glen Loy for sillimanite and feldspar
The sillimanite and feldspar occurs around the Glen Loy igneous complex. We followed the single track road which runs. along side the river until it starts to climb then park and walk down to the river. The sillimanite is quite easy to find as it is extensive and marked by geologist's core borings. We also found the veins of red oligoclase feldspar.
Glen Roy for the "Parallel Roads of Glen Roy" and garnet.
The "Parallel Roads of Glen Roy" are a glacial feature caused by the strand lines of a glacially impounded lake which occupied the valley at three distinct heights at the end of the last glaciation. Near the viewpoint car park a stream crosses the road and in it we found quite good-specimens of garnet mica schist.
Monday 4th August we continued up the west coast and then the SW of the Isle of Skye.
Carr Brae above Loch Duich for the Lewisian inlier.
(GA Guide 21 Lewisian and Torridonian of NW Scotland p90-92, OS Sheet 33, NG 897 246).
Here on the hillside is forsterite marble with diopside crystals, which weathers to large black outcrops and smaller outcrops of garnet-biotite gneiss. We also found a small outcrop of dark green eclogite.
Broadford beach for Jurassic fossils.
(Excursion Guide to the Geology of the Isle of Skye, p193, OS Sheet 32).
By Following the succession on the beach from east to west we started in the Lower Broadford Beds and went up into the Upper Broadford Beds, all of which is in the Lower Jurassic. The lower beds were hard marls and limestones. Much of the sand on the beach is composed of broken bits of the calcareous alga Lithothamnioncalcareum. We also found tests of the burrowing sea-urchin Echinocardiuincaudatum. Ammonites occur in the Upper Broadford Beds.
Kilchrist churchyard in Strath Suardal for skarns, marble and Cambrian limestone.
(GA Guide 13 Tertiary Igneous Geology of the Isle of Skye, pS and Excursion Guide to the Geology of the Isle of Skye, p189, OS Sheet 32, 617 207).
We walked along the road beside Loch Kilchrist to the Kilchrist dyke which we followed in a SE direction. There is a break in the dyke which affords a vantage point. From here we could see that there was a distinct vegetation change with heather on the granite and short grass on the well-drained Cambro-Ordovician dolostones. We followed the junction to the SW and located all four of the skarns using a compass as they are rich in magnetite, The skarns also contained garnet and some malachite. From here we continued SE across the heather to the marble quarry. We collected samples of the marble with its characteristic yellow-green streaks and wollastonite which formed from the silica in the limestone when it was metamorphosed.
On Tuesday 5th August we visited the north of Skye then returned to the mainland and continued up the West coast.
Old Man of Storr for basalt and zeolites.
(GA Guide 13 Tertiary Igneous Geology of the Isle of Skye, p22 and Excursion Guide to the Geology of the Isle of Skye, p247, OS Sheet 23, 499 539).
The Old Man of Storr is a slipped rock pinnacle. The basalt lavas that make up the Old Man and the rock face behind are clearly in layers representing different lava flows. The layers vary in the number and size of vesicles which has a bearing on the type of zeolite minerals in them. We looked through the scree between the Old Man and the rock face and collected a number of specimens. Stilbite was the commonest zeolite, but we also found chabazite, natrolite, laumonite and thomsonite. We also collected samples of red laterite which formed by the deep weathering of the upper layers of lava flows before the next one had erupted.
Kilt Rock a columnar-jointed sill with a waterfall.
(Excursion Guide to the Geology of the Isle of Skye, p256. OS Sheet 23, 509 655).
The view is of the cliff face to the north which shows good columnar jointing and
there are also complete columns which have fallen on to the beach.
The Quiraing for zeolite bearing basalt lavas.
(Excursion Guide to the Geology of the Isle of Skye, p266, OS Sheet 23, 44 68).
The footpath goes along the top a short way then slants down the face of one of the lava flows. We followed the path until we reached a scree slope which we went up and down. The first scree slope yielded little, but the second one was a lot wider with large boulders full of zeolite crystals.
Wednesday 6th August saw us continuing north on the west coast of Scotland.
Charlestown for the Loch Maree metasediments.
(GA Guide 21 Lewisian and Torridonian of NW Scotland p68, OS Sheet 19 NG 818 748).
From the car park, we crossed the bridge and took the first left due west. Along this trackway we identified the green amphibolites and brown biotite schists of the Kerrysdale series. We continued through a hay field to the one hill with prominent oak trees on top. This hill is composed of banded ironstone. Unlike most samples of banded ironstone which consist of red hematite and white chert this is partly metamorphosed so is black magnetite and white quartzite. We followed the path round to see low hills of marble and Flowerdale schists.
Knockan cliff for the Moine Thrust/Cambrian. contact.
(Knockan cliff geological nature trail. Assynt Geological Motor Trail, pS).
Geological Excursion Guide to Assynt District of Sutherland, p45, OS Sheet 15, 188
092.
Knockan cliff shows clearly where the Moine Thrust has pushed the older Moine rocks over the younger Cambrian. We looked at the rock specimens in the visitors' centre and also outside where they have built a miniature Knockan cliff out of cut and polished slabs of the correct rocks. We then walked down the road a short way to look at the Cambrian limestones and fucoid beds in situ.
Aultivullin Quarry near Borralan for pegmatites in the Loch Borralan intrusion.
(Geological Excursion Guide to Assynt District of Sutherland, p64, OS Sheet 15, 289 093).
The quarry is abandoned and set back on the north side of the road. The rock Borrolanite is composed of orthoelase, melanite and nepheline.
North end of Loch Awe where there is a quarry in Cambrian Fucoid Beds.
(Assynt Geological Motor Trail, p6, OS Sheet 15, 250 159).
The Fucoid beds are well exposed here and there are also good exposures of the Cambrian sucession at Skiag Bridge. We also studied Torridonian sandstone exposures on the right of Loch Assynt.
Achmelvich to look at the Lewisian.
(GA Guide 21 Lewisian and Torridonian of NW Scotland p40-42, OS Sheet 15 055 241).
We walked south to get to the cliffs above Loch Roe. Here there were blocks of hornblende and actinolite in the Lewisian gneiss.
Thursday 7th August we left the Lewsian and went to the Devonian of Caithness.
Loch na Fiacail to look at the Lewisian gneiss and pegmatites.
(GA Guide 21 Lewisian and Torridanian of NW Scotland p27, OS Sheet 9, 233 487).
Opposite the car-park is a large exposure, cut into the cliff by road-widening, of Laxfordian gneiss and migmatite with cross-cutting pegmatites. The gneiss is grey and the migmatite mainly pink, both are gently folded together. The pegmatites were every few metres and 20-30cm wide.
Baligill quarry to look for Devonian fish beds.
(Excursion guide to the Geology of East Sutherland and Caithness, p166, OS Sheet 10 NC 852 657).
The middle of this quarry is flooded and there are two fish beds exposed at the sides. The right hand side of the quarry has poor exposures but on the left side the exposures are good with a lot of slabs lying around. We found pieces of fish but the rock did not split easily. To be successful it would be necessary to remove large blocks and split them carefully.
Achananarras hill for Devonian fish beds.
(Excursion guide to the Geology of East Sutherland and Caithness, p131, OS Sheet 12, ND 150 544).
NOTE: Achananarras quarry is a world famous site for Devonian fish and a permit is needed to collect specimens.
This can be obtained by writing to:
Scottish Natural Heritage,
Old Forge Road,
Golspie.
We had a permit which limited us to 10 specimens. Achananarras Quarry is situated at the top of the hill, it is not very large and the middle is flooded. It was worked for the laminated limestone which was split for roofing slates. The site is littered with a vast amount of slabs which can be split with bolsters and hammers. Whole fish are rare and easily broken so we took back slabs to prepare later and all the pieces of broken ones to stick back together. We found examples of Osteolepis macrolepidotus, Gyroptychius agssizi , Dipterus valenciennesi, Coccosteus decipiens and Homosteus milleri.
Friday 8th August was when we set off down the eastern side of Scotland.
Brora to look for Jurassic coal, plants and other fossils.
(Excursion guide to the Geology of East Sutherland and Caithness, p53, OS Sheet 17,NC 905 032).
We found the Brora Roof Bed on the beach, a hard cemented sandstone and identified Jurassic fossils in it. The Brora coal was not exposed though.
Golspie for the Orcadian Stone Company.
The Orcadian Stone Company sells fossil and mineral specimens as well as guide books. The bulk of their business is cutting and polishing large pieces of stone for table-tops, signs and other things for sale.
Rogie Falls to look for a beryl pegmatite.
(OS Sheet 26, NH 443 585).
From the Rogie Falls car-park we walked east to the road cutting and on the north side of the road is a pegmatite about 5cm wide. The beryl is small and a very pale green, with muscovite which is 1-1.5cm across.
Little Scatwell for the old mica mine.
(OS Sheet 26, NH 385 572).
We took the minor road to Glenmarksie and part way up next to a Forestry Commission gate found a white boulder glittering with mica. We went through the gate and the overgrown hill on the right is the mine dump. The muscovite crystals are around 5cm across with quartz and feldspar from a worked pegmatite.
Portsoy for serpentinite and anorthosite.
(GA Guide 31 North-East Scotland: The Dalradian p6, OS Sheet 29).
We took a turning almost immediately on entering Portsoy to the left, signed to the swimming pool. Portsoy has a rocky beach, with near vertical rocks projecting into the sea at right angles to the cliff. The swimming pool is where they have built a concrete wall parallel to the land and joining two rock spurs together. It is possible to park on the beach next to the swimming pool. The serpentinite outcrop is just to the east of the parking space and the anorthosite is the single large rock outcrop in the middle of the next small bay just to the east.
Saturday 9th August we continued south on the East side of Scotland.
Ballater to look for the Abergaim lead/zinc mine with red sphalerite.
(Gerastone Sites of the British Isles, OS Sheet 44, NO 355 975).
From Ballater we went to Glen Gaim and followed the private road to the farm called Abergairn. After asking permission at the farm we visited the mine dumps above the house. There are lumps of green and purple fluorite and small pieces of reddish sphalerite but no good crystals. The only good crystals we found were of quartz.
Craigoshina in Glen Esk to find kyanite.
(OS Sheet 44, NO 574 764).
Craigoshina is a single house and it is necessary to ask the owner for permission to park and go up the hill side to the East. Near the top of the hill which is largely heather covered are bare patches where there are kyanite crystals of a good colour and about 5xl.5cm. Kyanite is also present in loose boulders on the hillside.
Ardownle Quarry near Monifieth for agates.
(OS Sheet 54).
Ardownie quarry is a large working roadstone quarry with agate and quartz in the basalt vesicles. As it is a working quarry we had to wear hard hats and obtain permission to enter. We found small geodes containing smoky quartz and amethyst crystals as well as agate.
Sunday 10th August was the last day of our trip and was spent in the Southern Uplands of Scotland.
Dob's Linn to look for Ordovician and Silurian graptolites.
(Geol. Exc. around Glasgow & Girvan p440, OS Sheet 79, NT 197 1S6 to 197 160).
The scree here is very extensive and in several places the Silurian is above the Ordovician so fossils can get mixed up. To study the place properly would entail careful sampling of the outcrops. However the site is an SSSI so we would have needed permission to hammer the outcrops and due to the amount of scree below them access to many of the outcrops would be difficult. We collected the Ordovician Climacograptus, Orthograptus, Leptograptus and the Silurian Monograptustriangulatus, Monogrptus crenulata and Monograptus fimbriatui, from the scree.
References
Barber, A.J., Beach, A., Park, R.G., Tamey, J. and Stewart, A.D. 1978 Geologists' Association Guide No. 21: The Lewisian and Torridian Rocks of North-West Scotland Benham and Company Limited.
Bell, B.R. and Harris, J.W. 1986 Excursion Guide to the Geology of the Isle of Skye.
The Geological Society of Glasgow. ISBN 0-902892-08-8
Berridge, N.G. 1969 Institute of Geological Sciences Report No. 69/5 A Summary of the Mineral Resources of the 'Crofter Counties' of Scotland. HMSO for Natural Environment Research Council. ISBN 0-1. 1-880096-5
Brown, G. M. 1969 Geologists' Association Guide No. 13: Tertiary lgnious Geology of the Isle of Skye. Benham and Company Limited.
Johnson, M. R. W. and Parsons, I. 1979 Geological Excursion Guide to the Assynt District of Sutherland. Edinburgh Geological Society. ISBN 0-904440-03-6
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Saxon, J. 1975 The Fossil Fishes of the North of Scotland. Caithness Books, Thurso.
Shelley, D.R. Asssynt Geological Motor Trail Sutherland Tourist Board
Stone, P., and Smellie, J.L. 1988 Classical areas of British Geology: the Ballantrae area: a description of the solid geologyof parts of 1:25 000 sheet NX 08, 18 and 19 HMSO for British Geological Survey. ISBN 0-1 1-8844l9-9
Stone, P. 1996 Geology in south-west Scotland. an excursion guide. Keyworth,
Nottingham: British Geological Survey. ISBN 0-85272-261-3
Trewin, N. H. and Hurst, A. 1993 Excursion guide to the Geology of East Sutherland andCaithness. Scottish Academic Press Ltd. ISBN 0-7073-0731-7
Read, H.H. 1960 Geologists’ Association Guide No. 31: North East Scotland: the Dalradian. Benham and Company Limited.
1986 Knockann Cliff geological trail Nature Conservancy Council. ISBN 0-86139185-3
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Gemstone Sites of the British Isles. Lapidary Publications.
Copyright Hull Geological Society 1999
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