This is the second of two field trips presented by the Geological Society of London, as a contribution to the celebration of the 125th Anniversary of the Geological Society of America. The trip is open to everyone who wishes to attend, including non-fellows of the Society.

The NW Highlands of Scotland is classic ground for structural geology. It was here that many of the key concepts were developed, from the recognition and analysis of thrust systems to the discovery of mylonites. The region remains an important test-bed for modern ideas in structure and tectonics, a training ground for the next generation of earth scientists and a home to analogues for faults in offshore oilfields. This five day field excursion aims to provide an overview not only of the geology and tectonics of NW Scotland but also a broad range of faults and shear zones. These chart deformation styles in the deep crust through various forms of mylonites and cataclasites right up to faulting and damage in analogue hydrocarbon reservoirs.

Excursion leaders

Rob Butler (University of Aberdeen)

Rick Law (Virginia Tech)

Both have over 25 years research experience on the structural geology and tectonics of the NW Highlands. Many of the outcrops and much of the context is provided by Geological Society Special Publication 335: Continental tectonics and mountain building: the legacy of Peach and Horne (edited by R.D. Law et al., 2010).

Further background can be found at the Assynt’s geology website

Itinerary outline

Sunday 2 June: meet in the afternoon/evening in Inverness (accommodation included) 
Monday 3 June: excursion begins , travelling to Kinlochewe, Gairloch, Gruinard and then onto Ullapool. Overnight in Ullapool.
Tuesday 4 June: Travel to Assynt and Laxford and then onto Tongue. Overnight in Tongue.
Wednesday 5 June: Visit the Thrust belt at Arnabol-Kempie. Overnight in Tongue.
Thursday 6 June: Travel to Sango and Portvasgo. Overnight in Tongue.
Friday 7 June: Travel to Eastern Moine, Portskerra (Devonian) and then back to Inverness by late afternoon. (Accommodation not included for this night)

Itinerary Content and Regional Aspects

• Crustal growth and syn-magmatic deformation together with amphibolites-facies shear zones in Lewisian gneisses. 
• Ductile shear zones, folding and associated deformation structures under amphibolite facies (the Moine)
• Classic mylonites in basement and cover rocks associated with the Moine and Arnaboll thrusts.
• Imbricate thrusts and duplexes in the Moine Thrust Belt.
• Cataclasitic fault zones associated with basin formation
• Fractured basement and sedimentary cover along the sub-Devonian unconformity: an analogue for the Clare oil field.
• Deformation of Jurassic sandstones along the margins of the Moray Firth basin system.
• Sub-Torridonian (late Proterozoic) unconformity
• The chief megasequences: Torridonian, Cambro-Ordovician, Devonian and Mesozoic.
• The Proterozoic Laxford Front
• The Caledonian thrust system, including the Moine Thrust Belt – a transect from foreland to orogenic interior.
• Post-orogenic basin formation and unroofing in the Old Red Sandstone

Images

Click on the links below to see images of some of the sights on this trip.

The Arnaboll thrust in its type-location. First recognised by Charles Lapworth, it was for this structure that Geikie first coined the term “thrust” (1884) and Lapworth first described mylonites (in 1885).

FracTrias: fractured pebbles in basal Triassic conglomerate, deformation at the base of a sedimentary basin.

(Main photograph) The classic view onto the Glencoul Thrust, first described by Charles Callaway in 1883, one of the major structures of the Moine Thrust Belt.

Laxford: sSheared gneisses and acid-igneous sheets deformed during “Laxfordian” (Proterozoic) period major zone of crustal reworking of Laurentia.

Lothbeg: minor fault arrays disrupt interbedded sandstones and shales of mid-Jurassic age, seen in outcrops on the edge of the Moray Firth.

Vasgo folds: recumbent intrafolial folds within ductile thrust zones that rework Moine psammites, part of the range of deformation structures developed in these mid-crustal shear zones.

Further Information

The cost per participant for this excursion is 450 GBP. This includes:

• Accommodation with breakfast for 5 nights (2 - 6 June)*
• Dinner on the three nights in Tongue
• Transportation in the field (excluding to and from Inverness)**
• A copy of the field guidebook.

* In order to accommodate as many attendees as possible, and to keep costs to a minimum, most the accommodation has been booked on a twin-room sharing basis.

** Participants will need to make their own travel arrangements to get to and from Inverness. There are direct flights from London to connect with international flights and also a rail service (including sleeper accommodation, but not over Saturday night).

The field excursion involves a combination of landscape views and hands-on outcrops. Although some of the outcrops are readily accessible at the roadside, most involve some hiking. The maximum distance of any one hike is around 5km and most are less than 1km from parking places. However, the terrain can be damp and rough in places so although high levels of fitness are not required, reasonable levels of mobility are!

The field excursion dovetails with ‘The Great British Tertiary Volcanoes: Exploring the Palaeogene centres of Skye and Rum’ excursion led by Dougal Jerram et al. This will finish in Inverness on Saturday 1 June. For individuals wishing to participate in both excursions,  we would  arrange a day’s geology, local to Inverness, at minor additional charge. We will help find accommodation in Inverness on 1 June, but participants will need to cover this cost.

Registration

Registration for this trip is now closed. If you would like to be added to a waiting list then please email Naomi Newbold.

The Geological Society of America are also holding the following events which you may be interested in:

Roof of the World - Joint Scientific Meeting of the Geological Society of China and The Geological Society of America, 17-19 June 2013