Shetland 2015

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.

The island of Uyea in the distance has gneisses that were fomed 2.7 Ga.

The island of Uyea in the distance has gneisses that were fomed 2.7 Ga.

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.

Is this a pebble of basement in the cover immediately above the WKSZ? (photo Tati Penteado Sitolini)

Is this a pebble of basement in the cover immediately above the WKSZ? (photo Tati Penteado Sitolini)

Not to mention the best lunch spot of the trip on the Fethaland Peninsula, where ‘basement’ and beautifully garnetiferous Moine-equivalents are interleaved.

Looking towards Fethaland. Enjoying lunch and anticipating some lovely garnets!

Looking towards Fethaland. Enjoying lunch and anticipating some lovely garnets!

Do you know who loves garnets? Dr Anna Bird.

Do you know who loves garnets? Trip leader,  Anna Bird.

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!

Discussing deformation caused by the Walls Boundary Fault, seen in the background (Photo Steph Walker)

Discussing deformation caused by the Walls Boundary Fault, seen in the background

Is this the med? No, Shetland of course! (Photo Ian Millar)

Is this the med? No, Shetland of course! (Photo Ian Millar)

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!

'Go and look at those rocks, they're amazing' is no doubt what Anna's saying.

‘Go and look at those rocks, they’re amazing’ is no doubt what Anna’s saying.

And she was right!

And she was right!

Next was the Valayre Gneiss, a beautiful augen gneiss formed in the Neoproterozoic and deformed in the Ordovician.

trip leader Rob Strachan dancing, sorry, describing a shear zone in the quarry wall.

trip leader Rob Strachan describing a shear zone in the quarry wall (Photo Anna Bird).

The Valayre Gneiss in all its splendour (Photo Clare Warren)

The Valayre Gneiss in all its splendour (Photo Clare Warren)

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.

Rob in his natural habitat, striding ahead of the group.

Rob in his natural habitat, striding ahead of the group at Brekon Sands.

What caused the steep fabrics in Yell?

What caused the steep fabrics in Yell? (Photo Tati Penteado Sitolini)

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!

Agmatitic textures in the Westing Group. Deformed at around 930 Ma

Agmatitic textures in the Westing Group. Deformed at around 930 Ma

Trip leader Steph Walker points out a Kyanite to Mike Dunk

Trip leader Steph Walker points out a Kyanite to Mike Dunk (photo Anna Bird)

Rob outlines the metamorphic history of northern Unst.

Rob outlines the metamorphic history of northern Unst. (Photo Clare Warren)

In order to help digest this complex information, some member of the party resigned to consider a different sort of Auld Rock.

Tyler Ambrose, Rob, and Derek Rushton deep in discussion about the complexities of ophiolite emplacement models

Tyler Ambrose, Rob, and Derek Rushton deep in discussion about the complexities of ophiolite emplacement models

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.

Over the sea to... Fetlar. (photo Tati

Over the sea to… Fetlar. (photo Tati Penteado Sitolini)

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.

Getting a soaking all in the name of metamorphic geology.

Getting a soaking all in the name of metamorphic geology. (photo Jane Evans)

the metamorphic sole of the ophiolite with relict grt-cpx assemblage (Photo Clare Warren)

The metamorphic sole of the ophiolite with relict grt-cpx assemblage (Photo Clare Warren)

Rob discussing his ideas as for the emplacement of the Shetland ophiolite.

Rob discussing his ideas as for the emplacement of the Shetland ophiolite.

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.

Strained clasts in the Funzie conglomerate.

Strained clasts in the Funzie conglomerate. (Photo Clare Warren)

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.

Ok, yes. It was rather 'bracing'.

It was rather ‘bracing’. (photo Ian Millar)

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!

Key of E? (photo Ian Millar)

Key of E? (photo Ian Millar/Jane Evans)

The race was on to get there before they stopped serving breakfast rolls!

The race was on to get there before they stopped serving breakfast rolls! (Photo Ian Millar/Jane Evans)

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.

Last outcrop of the week, and some sunshine to go with our steep foliations.

Last outcrop of the week, and some sunshine to go with our steep foliations.

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!

Trip members in front of the Walls Boundary Fault

Trip members in front of the Walls Boundary Fault

Words and pictures, unless otherwise stated, by Steph Walker.