The Top Twenty Geological Sites in the Isle of Mull, by James Westland MSc (Part 2)

Posted by True Highlands in Kit and Caboodle | 6 comments

Whether you’re a keen geologist or just interested, there is no doubt that geology fascinates.

These geological sites are simply the author’s choice of interesting places to visit. They are listed in the order of an itinerary, starting at Tobermory, travelling west and south and ending up in Iona.

Part 1 of The Top Twenty Geological Sites in the Isle of Mull, by James Westland MSc can be found here.

11. Fossil Tree

The famous Fossil Tree, sometimes called McCulloch’s Tree after the geologist who first described it lies at the very point of the Ardmeanach peninsula, on the Burg Estate, owned and managed by the NTS. The tree is one of several that were caught up in a Palaeogene lava flow 60 million years ago. Some of the original wood still exists but most of what is visible is the cast of the trunk. Spectacular. Note the walk to it is rough long and very steep in places. Care needs to be taken.

12. Carsaig fossils

Carsaig Bay lies on the south coast of Mull and is easily reached by a steep road from Pennyghael. There is so much interesting geology in this one area , it is difficult to know where to start.  On a rocky platform, to the east of Carsaig Pier and accessible by a sometimes muddy track, there are numerous casts of ammonites to be seen, some of them quite large. Ammonites, now extinct, were found in the Jurassic seas when dinosaurs roamed the land. Further west in Carsaig Bay, the beach is littered with Gryphaea or “devils toenails”. In the same area, belemnites, which look like small bullets can be found. A fascinating place.

13. Carsaig Arches

This involves a long and strenuous walk from Carsaig Pier. Not for the unfit or faint hearted! There are two arches, one of which is a large cave, the second a sea stack. Columnar basalt overlying ash beds can be readily seen here.

14. Ardtun

Ardtun is famous for its fossil leaf bed which dates back to Palaeogene (early Tertiary) times. Although the leaves are not so easy to find these days, the location is spectacular and the columnar basalt formations are superb. Great care is needed in approaching this area – the ground is boggy and the leaf bed is down a steep gully. The gully is called “Slochd an Uruisg” – the goblin’s hollow!

15. Ardalanish Bay

Aralanish Bay is famous for its metamorphic rocks and the unusual minerals that are found there. Kyanite and Tourmaline are both to be found, but this is an SSSI, so no hammering please! Large garnets are also found, in a rock called amphibolite. However, they are not of gem quality unfortunately!

16. Ross of Mull Granite contact

This is beautifully exposed just west of Ardalanish Bay and clearly shows how the granite has intruded and broken up the Moine schists. Great slabs of schist appear to float in the granite – one can imagine the process at work as the molten granite invaded these metamorphose sedimentary rocks and split them asunder by a process known as “stoping”.

17. Ross of Mull Granite at Fionnphort

Just south of the slipway at Fionnphort, the granite is beautifully exposed – here a secondary  intrusive rock is seen which rejoices in the name “porphyritic microgranodiorite” – a darker rock which cuts across the pink granite and. Pieces of the granite are found enclosed by the PMD and vice versa.

18. Iona Glacial erratic

Iona is covered in erratic boulders, that is great lumps of granite that have been carried westwards by the glaciers that once covered the area. All the errratics are found west of the granite, not east, thereby indicating the direction of ice flow.

19. Iona Columba’s Bay

A great spot – the colourful rocks and pebbles that make up the shingle beach where St Columba supposedly landed after sailing from Ireland, are a delight. Search the beach at the waters edge and see if you can find any of the yellow-green serpentine marble stones that are common here. Dont confuse them with the much more common epidote-green pebbles which are much more common. The Iona marble is yellowish; the epidote is pistachio green!

20. Iona Marble Quarry

A piece of industrial archaeology. Located in the south east of the island, this is a wild spot where the marble was once worked. Much of the old machinery is still lying about and hug blocks of pure white marble abound. The marble is a very pure form of metamorphose limestone, over 2000 million years old.

Grid References

11           Fossil Tree                                            NM403277

12           Carsaig – Fossil Ammonites           NM556210

13           Carsaig Arches                                    NM495184

14           Ardtun                                                  NM379247

15           Ardalanish                                            NM373186

16           ROM Granite contact                        NM367179

17           ROM Granite Fionnphort                  NM298232

18           Iona Erratic                                          NM283233

19           Iona Columbas Bay                             NM263216

20           Iona Marble Quarry                            NM266216