Mull Geology

The Doirlinn (or Doirlinn a'Chailbhe) is the narrow channel between Mull and the Island of Calve, which is well seen from Tobermory. At the lowest of tides, it dries out and you can walk across from mainland Mull to Calve Island. Today at lunchtime was an opportunity to do just that. As a tidal feature, the Doirlinn is interesting, but the geology also has something neat about it. It is one of only a handful of places in North Mull where the underlying Mesozoic rocks can be seen - Most of North Mull is covered in volcanic rocks, mainly plateau basalts of Paleogene age, cut by numerous minor intrusions (dykes and sills) However in a few places the older rocks on which the basalts have been deposited, the Mesozoic, can be see peeping out. The other places are north of the lighthouse at Rubha nan Gall, south of Tobermory near the Guala Dhubh and north of Tobermory at Bloody Bay, where the rock was once quarried. I had a good look at this stuff today - below are some photos: ...

The final location I visited a part of my short trip to the Ross of Mull was to Torr na h-Anaid next to Bendoran Cottage near Bunessan. This is another classic locality where sillimanite is found in the metamorphosed Moine rocks close to the contact with the granite. In the Zaniewski paper I mentioned previously there are some interesting features to be seen at this location. It doesnt take long to visit as it close to the road. Last time I was on this actual site was in November 1979 as an undergraduate! Heres the view from the road (Google Streetview as I didnt take a pic of the hill: View from the road up to the hill Torr na h-Annaid is famous for the development of sillimanite near the contact. After searching about for a bit, I found some rock surfaces where it clearly forms "knots" Sillimanite knots in the Moine schist - ruler for scale There was also a small vein of pegmatite nearby:  Vein of pegmatite cutting the schist And a clos...

Final day of the short geologising trip to explore the Ross of Mull Granite. Classic locations, today's was one of the best - Knockvologan and the coast opposite Erraid Island. Bitingly cold wind but beach was deserted. After spending the morning there I went up to Bendoran Cottage to have a look at the other classic ROMG/ Moine contact on the hill behind the cottage. More of that later, but here are some pics of the Knockvologan area with some brief details (I used the VMSG 2017 Guide. I was on the VMSG field trip last year and Knockvologan was one of the places we visited. However there were a few locations that werent included then so I had a look today) First stop to look at the distinctive aplite vein running through the granite near the shore  The aplite vein runs across the rock face  In close up The granite is very coarse with large K-feldspar phenocrysts. RM2 facies The area is famous for the diorite enclaves in the granite. All sorts of interactions...

Continuing my visit to the Ross of Mull, todays walk was to Ardalanish - one of my favourite places. First visited here in Nov 1979 as an undergraduate from St Andrews on what was a wet week for field work. I have been back loads of times but what I wanted to do was to check some of the details with a couple of papers. I was interested in looking at the contact of the Moine rocks with the Ross of Mull Granite (ROMG)  - there is a GCR report on this area as well as a very good paper by Zaniewski, Reavy and Harris published in the Scottish Journal of Geology 2006. I had both of those with me for reference. Fun guy to have on a walk eh? :) Anyway, the weather was great and since a picture tells more than I can,here are some shots of the area: Still a bit hazy,Ardalanish bay. Moine rocks form the hillocks, Cliffs in the distance are Paleogene basalts near Carsaig Arches Down on the shore - this is a pic of one of the locations in the Zaniewski paper - Moine rocks on the right...