Garnets, an Ophiolite, and a load of Auld Rock
The first MSG trip in ~10 years took place in Shetland in July 2015, led and organised by Rob Strachan (Portsmouth), Anna Bird (Hull), and Steph Walker (Royal Holloway). 20 students, academics, and interested others converged on Lerwick Ferry Terminal early on a Friday morning for a week of exploring the geology of Shetland, ranging from the 2.7 Ga basement gneisses to the c. 400 Ma Caledonian overprint.
Day 1 included some mild excitement in the form of lost luggage and party members, but all was made well by a bracing 8km walk to look at the oldest rocks in Shetland near the island of Uyea in northern Mainland.
Day 2 was spent looking at cryptic Neoproterozoic shear zones and a hunt for the Moine Thrust. These pebbles suggested to members of the trip that the Wester Keolka Shear Zone, a structure often considered as the Moine Thrust, was actually just a sheared unconformity.
Not to mention the best lunch spot of the trip on the Fethaland Peninsula, where ‘basement’ and beautifully garnetiferous Moine-equivalents are interleaved.
The excitement was only getting started as day 2 also included a trip t0 the Walls Boundary Fault (The Great Glen Fault, extended to Shetland). The sun was making people giddy, and much swimming and paddling was undertaken. After a serious look at the excellent structures, of course!
Day 3 took us to Lunna Ness and into the Yell Sound Group. Truly spectacular migmatitic and decompression textures led to some very excited metamorphic geologists!
Next was the Valayre Gneiss, a beautiful augen gneiss formed in the Neoproterozoic and deformed in the Ordovician.
Yell was calling on Day 4 and to the Sands of Brekon, leading to discussion as to what caused the steep fabrics here in Yell.
On day 5, we were headed to the lovely island of Unst, where some very complex geology, including at least 3 different structural blocks of very different metamorphic rocks and an ophiolite led to lots of head-scratching!
In order to help digest this complex information, some member of the party resigned to consider a different sort of Auld Rock.
Day 6 brought the group to the ‘Garden of Shetland’ – the island of Fetlar. As we were staying on Unst, another ferry was in order.
First, we went to look at the grt-cpx metamorphic sole of the ophiolite on the north coast of Fetlar. This involved some very daredevil descents down long, steep, grassy cliffs, but all members of the group made it, and they were not disappointed by what they found, despite the crashing waves.
Of course, no trip to Shetland is complete without a visit to the Funzie Conglomerate, where Derek Flinn developed his seminal work on strain analysis.
Returning to Unst for the night with the seemingly never-ending daylight and sunshine, some of the more hardy (mad?) members of the group couldn’t miss the opportunity to go swimming on the most northerly beach in Britain. And whilst Anna and Steph were representing the trip leaders in the sea, Rob stoically stayed out of the water to ‘look after the car keys’. Cheers, Rob.
As we left the Northern Isles on the last day of the trip for a short tour of the Dalradian of Mainland Shetland, there was some time for a musical interlude at the Unst Ferry Terminal boat xylophone, and a fleeting visit to the Brae fish and chip chop for 20 much coveted bacon and egg rolls!
The geology of Central Mainland is dominated by Dalradian equivalents, and the coast near Scalloway is the perfect place to see them being intruded by syn-tectonic pegmatites.
All that’s left is to thank all that came on the trip for making a memorable and interesting one! Of course, a lot can be said for an intensive week looking at some fantastic geology, but often the after-dinner session in the bar is where the best ideas are thought up.
So here’s to the next MSG field workshop, where like-minded metamorphic aficionados can get together and learn more about their field, in the field!
Words and pictures, unless otherwise stated, by Steph Walker.