Tuesday, 7 January 2014

Field Geology on the Outer Hebrides & in Northern Scotland

Dr. Nick Chidlaw is currently offering two 1–day courses for next March; these are indoor-based, and describe field areas to which he has run courses in the past. They may be attractive particularly to people who are not in a position to visit these field areas, e.g. insufficient time available because of family / work commitments, or health problems.
Each course would comprise powerpoint-based lectures, together with examination of hand specimens of relevant mineral and rock types, and published geological maps of the field areas. The hand specimens have been collected by the tutor in the field areas described. 
The venue would be in the Buckingham Room (single storey building by the car park) at The Chantry, 52 Castle Street, Thornbury, South Glos. BS35 1HB.  Tel: (01454) 414268. See venue website for further details, including location map. On each course attendees would bring their own packed lunch and other refreshments, or go into the town for lunch.
These two 1–day courses have a fee of £25.00 each. 

If you / anybody else you know, would like to attend either or both of these offered courses, please contact Nick.
Please note: these courses are to run on the same weekend, but are independent of each other; you can enrol on both if you wish to, or one of them, according to your interests / availability.  
The deadline for the minimum number (10) of enrolments is Saturday 8th February (4 weeks before the courses are due to run). Maximum number of attendees 30. If the minimum number for each course is reached by this deadline, the arrangements will be able to continue, if not, the course(s) not reaching viability will be cancelled, and fees received will be returned to those who sent them in, soon after. Enrolments above the minimum numbers for each course will be able to continue for up to 1 week before it is due to run.  

Saturday 8th March. 10.00 am – 5.00 pm
The Outer Hebrides (also known collectively as the ‘Long Island’) off NW Scotland are some 130 miles in length, possess striking landforms, and are underlain mostly by the oldest rocks in the British Isles. This day course will introduce you to these islands, from the largest, Lewis, in the N with its rolling moorlands, through the mountainous Isle of Harris, the diverse country of the Uists and Benbecula, to the rocky island of Barra in the S. The hardness of much of the bedrock, former glacial cover and subsequent marine erosion have created widespread exposures; both coastal and inland. Here are found the most extensive outcrops in the British Isles of the Lewisian Complex, parts of which were formed around 3000 million years ago, over half the age of the earth itself. These rocks have similar characteristics and geological history to parts of northern Canada and Greenland, to which they were once joined. Today, the Lewisian Complex is understood to be composed of a series of distinct crustal units or ‘terranes’, which were formed / progressively amalgamated, through a series of plate tectonic collisions between 3000 – 1500 million years ago. Subsequent erosion has removed great thicknesses of these rocks, so that today we can walk across what formed 10s kms below the crust’s surface in high pressure/high temperature environments: including varieties of gneiss with striking deformation structures. In Permo-Triassic times, around 300 - 200 Million years ago, the British crust was being stretched as the North Atlantic Ocean Basin began to form. Rift basins developed to the E and W of what is now the Outer Hebrides, into which sediments accumulated, under a hot desert climate. Near Stornoway on the Isle of Lewis, occurs an arm of one of these rifts, providing the only place on the Outer Hebrides where these rocks can now be studied on land. 
A handout outlining the day’s programme, and a list of optional suggested reading, will be provided on the course. No prior knowledge of geology or the study area is assumed. 

 Sunday 9th March. 10.00 am – 5.00 pm.
 In late Precambrian times, c. 750 million years ago, northern Scotland was located in the mid latitudes of the S. hemisphere, and was part of a large area of continental crust comprising much of what is now Greenland, N America, Scandinavia and northern S America. Across this continental mass a linear zone of plate tectonic extension was developing, within which lay the crust that is today northern Scotland. The crust that now lies between Scotland’s Great Glen in the N, and the Highland Border in the S, began at this time to stretch, rupture, and episodically subside, and sediments began to be deposited on top. This tectonic setting and accumulation of sediments continued into Early Ordovician times, these strata forming the Dalradian Supergroup, over 25 km (15 miles) thick. The Dalradian Supergroup records a wide range of environments from river plains to deep sea, and are locally interbedded with volcanics and metalliferous ores; some of these strata represent glacial deposits laid down during submarine avalanches. In Mid Ordovician times, a plate tectonic collision event, known as the Grampian Orogeny, affected the Dalradian Supergroup: in some areas there was little deformation and alteration, but in others the rocks underwent intense deformation to form colossal folds and faults, and some were metamorphosed to the point at which they began to melt.
A handout outlining the day’s programme, and a list of optional suggested reading, would be provided on the course. No prior knowledge of geology or the study area is assumed.

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