GEOL2026 Report Maximilian RichardsIntroductionThe area in question is situated in the county of the Highlands, situated on the North West coast of Scotland, UK.. The main geological feature present is the Moine Thrust Belt which has moved over a variety metasedimentary and mylonitic rocks from many miles to the east – a zone of crustal shortening, and extensive faulting. It demonstrates the Caledonian orogeny of the Silurian period, a period of compression. The Moine Thurst is known to geologist throughout the world as a classic example of a large scale thurst zone.
The zone extends from the Point of Sleat in Skye, in the south to Whitenhead on the north coast of Sunderland – a distance of around 200km(See figure 1). The locality mapped on this excursion covers an area of 2km2, along the this thrust – situated around Ben Arnaboll. This area is described as the ‘Cradle of Geology’ where many of first the important geological ideas were developed by pioneering geologists Peach and Horne, such as the idea of ‘mountain building’. The work being done in the area in question is to demonstrate an understanding of the underlying geology processes and features that have given rise to such a diversified landscape. The mapping was done over the course of 3 days, a range of measurements have been taken – such as the localities of outcrops, the strike and dip of strata, and structural observations. This report contains field descriptions of observed strata, structural observations, the discussion of the underlying tectonic themes and a conclusive summary. The area is underlain by Lewisian basement rock. It contains the oldest rocks in Europe (Lewisian Gneiss), being 3 billion years old.
The general succession shows a native sedimentary deposition of rocks ranging from the Ordovician to the Archean. The climate of North West Scotland is mild. In spite of high latitudes (58.5) the summer experiences exceedingly warm temperatures considering this, however, in the winter, it is very cold with temperatures as low as -10® and frequent snowfall on the highlands. Temperatures vary day to day over a large range. The terrain is rugged in the area in question, with steep mountains, V-shaped valleys, and large lochs dotting the landscape. There are a range of publications on the theories, themes, and geology of the area in question.
The area has been extensively studied for the last century, it encapsulates a range of geological themes. Beginning with the studies of MacCulloch between 1814-24, followed by the systematic mapping of the area by the Geological Survey following 1885. The development of the theory of the stratigraphy and the structure of the area was developed by Horne and Peach in the early 20th century. More recently J Christie in the 1960s wrote of developing theories left undeveloped by the Geological survey in the publication ‘The Moine Thrust Zone’. Friend, C. R.
L. & Kinny, P. D in their publication ‘Reappraisal of the Lewisian Gneiss Complex’ discuss themes pertinent to this publication, such as the tectonic assembly of the area, and the current model for the evolution of the complex as a whole. As well as this the information presented in this publication dates the age of the Gneiss.
Gilbertson, D., Kent, M. & Grattan, J in their publication ‘The Outer Hebrides’ discuss the historical themes influencing the area as well as the influence of glaciation on this area. Goodenough, K.
M. & Krabbendam, in their publication ‘Digital surface models and the landscape: interaction between bedrock and glacial geology in the Ullapool area’ discusses distinct sequences characterised by the landscape of the area. The paper considers the influence of bedrock geology in the area. Hambrey, M.J., Fairchild, I.J., Glover, B.
J., Stewart, A.D.
, Treagus, J.E. & Winchester, J.A. in their publication ‘The Late Precambrian Geology of the Scottish Highlands & Islands’ give a concise overview of the geological themes of the area. In addition to this the British Geological Survey have produced an in depth 3D model of the Assynt base area. Many publications have been written over the last 130 years, developing theories touched upon by the research done before them, this area is extensively studied and well understood by geologist. ResultsFormations from oldest to youngest The first horizon found, page 14 of the notebook.
See figure 2.Rock is grey with small amounts of brown in banded layers, it is composed of white feldspar and quartz. The white bands contain mafic minerals such as biotite mica. It is medium grained with small quartz veins. Crystals are coarse, very finely foliated. The mafic minerals are arranged in a streaky banding giving it a gneissic texture. The rock contains veins of pink granite. Thickness is unknown’.
This horizon is isolated to the east side of the map. A hanging wall is observed with its interaction with horizon 4, presenting an unconformity. The horizon stands higher in terms of elevation. Within this horizon there are commonly observed banding that trends north-west. The foliations are characterised by alternating darker and lighter coloured bands (See figure 2). This is instinctive of a highly metamorphized rock.
Within this horizon examples of highly sheared low grade rocks typical of mylonites can be observed. The shearing runs in a north easterly direction. Shows evidence of recrystallization, Indicates two periods of metamorphism. Lineation’s within the horizon plunge at low angles towards the south east. Different grades of horizon 1 can be seen among the south west of the map – some outcrops were darker and instinctive of ultramafic instead of mafic. The average dip of horizon 1 was, in an easterly / south east direction. These observations were made at location 29, on page 35 of the notebook.
The second horizon found, page 22 of the notebook, location 14. (See figure 3).Rock is described as ‘80% quartz, crystals are fine to coarse-grained – massive. White/grey with some brownish elements, vitreous. Evenly textured, metamorphic and some feldspar.
Does not scratch with a steel knife. Hard. Cross-bedding present. Grains appear rounded. Thick beds, visible up to 15m. Glaciation striations appear, in north westerly direction’. Horizon only found in the south west of the map.
Horizons are steeply dipping with a typical thick of around 80 degrees. The third horizon found, page 23 of the notebook, location 16. (See figure 4 and 7).Rock is described as ‘Redish in colour, has ‘pipe’ shape appear to be vertical burrows ranging in size from 1-5cm in height, distinctively colour white.
White quartz visible, fine to medium rained. Biological markers in rock are great for bioturbation’. ‘Some stains observed – purple and brown – suggests iron and manganese oxide. Massive’.
Appears dolomitic in nature. Thickness visible to about 15m. Dip varies between map with formations in the central east dipping between 34-37 degrees, observed horizons in the north having larger more pronounced dips of around 65 degrees. Widespread throughout the map. The fourth horizon found, page 26 of the notebook, location 17.
(See figure 5). Rock is described as ‘Extremely fine-grained, weathers dark orange/brown, calcareous – fizzes under acid, not that strongly. Rock is ‘softish’. Must be relatively rich in carbonate, sedimentary, flakey and instinctive of a shale’. Outcrops up to 15m thick.
Average dip – 30 degrees. Horizon is widespread throughout the map, frequently found in conjunction with horizon 5. Anti-cline observed in face of horizon in the north east of the map.(See figure 6).The fifth horizon found, page 28 and 36 of the notebook, location 20. Rock is described as ‘Light grey/brown, gritty.
Fairly coarse, even grained. Very hard – steel knife does not scratch, high amounts of quartz visible. Some cross bedding’. Page 36 describes ‘Some small shelly fossils visible in (horizon) ‘.
Contains false bedded grit with occasional pipes – similar to those found in horizon 4. Quartz is mature. Horizon is widespread throughout the map.
Outcrops up to 10m thick. Average dip of 35 degrees. The sixth horizon found, page 28 of the notebook, location 21. Rock is described as ‘Dolomitic in nature, dark finely grained, brownish.
Made of plagioclase. Some banding visible. Fizz test with acid done. Did not fizz on exposed outcrop, however, a fresh cut piece does fizz. Carbonates present, dip is 30 degrees’. Horizon isolated to the north west.
Formations vary in thickness, largest seen is 30m. Discussion The Discussion of your results: infer environments of deposition and climate from the rock types, sedimentary structures and fossils, the tectonic features give the clue to the history of the area after the rocks were laid down. For igneous rocks and metamorphic rocks, include information on the protolith. Relate your observations and results to the published work: ‘My Unit X is equivalent to Formation Blah-blah because …
‘ If you mention someone else’s work or ideas reference it. Only discuss what you can deduce from your own observations in the 2 km2 you mapped.