In April, PhD students Phil Slay and Issy Siggers joined the first year fieldtrip to Arran as demonstrators. In this blog post, they recount the trip's highlights – from the mapping day in Glen Sannox, to fossil archosaur tracks and the infamous 'Doon' igneous sill.
It was Day 1 of the Arran fieldtrip, and we started the morning admiring pillow basalts on the Ayrshire coast before taking the ferry across to the island.
On arrival in Arran, we headed to Lochranza where we had our first look at the much loved Dalradian metamorphic rocks – the perfect introduction to a week exploring the island’s fantastic geology!
On the following day we started in North Glen Sannox. The intermittent drizzle didn’t dampen our excitement for the granite-Dalradian contact! We were especially excited to see fragments of Dalradian within the granite (pictured below), likely fractured off and incorporated during the intrusion of granitic melt.
Day two: North Glen Sannox (left), the granite-Dalradian contact (middle) and a glacial erratic boulder (right).
Down the valley, we visited some of the other units the students would map on day 6, eventually emerging onto a lovely coastal path cut into the Old Red Sandstone.
On the way to our final few stops, we passed a few glacial erratic granite boulders before ascending an extremely muddy path (a gift from previous geologists visiting this locality!) to look at limestones containing many exceptionally large brachiopods in life position, as well as some coral! Truly worth the muddy boots that unfortunately had to be worn onto the coach back to the field centre (our apologies driver Mike).
Today (day 3) we embarked on a grand tour of the island, starting in Kildonan with our first igneous dykes (discordant intrusions) of the trip. These formed when Europe began splitting from America about 60 million years ago!
We also looked at the ‘country rock’ around the dykes – Triassic sandstone and mudstone containing the footprints of an archosaur (Chirotherium), a crocodile-like creature that walked on the surface 240 million years ago (see photo below).
Examining igneous dykes on the foreshore and the footprints of an archosaur (right).
We continued our lap of the island along the west coast, checking out the infamous Dalradian rocks.
We found funky kink banding at Imachar Point and lovely phyllite at Rubha Airigh (affectionately known as rhubarb custard to some!). The phyllite had compositional banding and plenty of muscovite, chlorite and epidote.
We finished up at Lochranza Pier with the students locking in their compass-clino skills ahead of mapping later this week!
Taking a look at the funky kink banding at Imachar Point.
Day 4: a big day spent traversing the north coast of Arran. Starting at the world-famous Hutton’s Unconformity, where pre-Cambrian Dalradian meets Devonian Old Red Sandstone, we saw just how complex unconformities can really be in the field.
We then jumped to the Carboniferous to examine a fallen block containing a fossil Lepidodendron (a large-tree-like plant). After crossing the An Scriodan boulder field, we moved into the Permian New Red Sandstone to admire the stunning aeolian dune formations.
Lunch coincided with our stop at the fossil-rich Index Limestone. One student found a trilobite pygidium, and the group also saw productids, spirifids, rugose corals, crinoids and bryozoa fossils. Lecturer Ed Tipper then pointed out fossil tracks left by an Arthropleura (a giant Carboniferous millipede!).
Students examining Hutton Unconformity (left), a Lepidodendron fossil (middle) and fossils in the Index Limestone (right).
We then had a look at an ash flow containing volcanic bombs, which would have been formed in an explosive volcanic eruption.
Finally, we climbed the saddle, admiring the views of Firth of Clyde and the mainland before heading back to the field centre for a hearty dinner. What a day!
Day 5 was a true highlight of the trip – visiting the iconic Drumadoon sill! We admired this solidified magma body (a quartz feldspar porphyry) up-close, sketched it from afar and studied the nearby dykes.
Later, we visited King’s Caves – the potential hideout of Robert the Bruce – and thought about how the much more recent (geologically speaking!) glaciation of Arran affects the landscape we see today.
Heading toward Drumadoon Sill for a closer look.
Day 6: the all-important mapping day! We returned to North Glen Sannox, where the student’s task was to map the rock units and interpret the geological history of the valley.
We also had a group doing some geochemical mapping, sampling the pH of the burn and its tributaries. We were lucky – the sun shone all day and we washed down our lunch with a refreshing can of cold Irn-Bru!
In the evening, the students finalized their geological maps and cross sections and presented a range of exciting interpretations.
On our final day on Arran, we ran two fun options for the students. One group hiked north from Clauchlands Point to investigate some beautiful igneous units not seen elsewhere on our trip, including a microgabbro (dolerite) sill, hexagonal columns, pitchstone and country rock baked margins. Whilst having lunch on the beach, some lucky students found agate pebbles!
Rounding off the trip with two options: investigating igneous rocks at Clauchlands Point (left), and a hike up Goat Fell for island views.
The rest of the group hiked up from Corrie, first to North Goat Fell and then along the ridge to Goat Fell peak, where the clear weather meant we could see right across the south of the island toward the barely-visible Ailsa Craig. We then joined the other group for refreshments and ice-cream by Brodick Castle.
In the evening, trip leader Ed Tipper gave the students a talk summarising the rich geological history of the Isle of Arran, before the group retired for the evening to pack and to enjoy the gorgeous sunset.