WEGA in the North West Highlands Geopark

Day 2 – Monday 29th April 2019

Our first stop was at Achmelvich where we were to look at the Lewisian. But what we looked at first was the wonderful beach. It looked its wonderful best – blue skies, blue sea, white sands. And the temperature was reasonable!

The group on Achmelvich Beach

We were headed towards some Lewisian Gneiss with a cross-cutting Scourie Dyke. The gneiss is about 2,400Ma, the dyke “only” 2,000Ma.

The dyke textures remain unaltered but there is some minor shearing along the edges.

The Scourie dyke. The two outer persons are on the Lewisian Gneiss.

After observing  (or being observed by) some Sea Eagles we walked over the headland to look at some more Lewisian.

Lewisian Gneiss
Lewisian Gneiss
The path to the beach - an eroded out Scourie dyke with Lewisian gneiss on both sides. Sediments being laid down.

We then moved on to Clachtoll where we came across a formation which was new to me – the Stoer Group. This is a rock very similar to Torridonian but which underlies it and is 200Ma older.

It lies unconformably on the Lewisian, with its lowest members being a basal breccia.

Stoer Group basal breccia lying on Lewisian. The contact may be steeper than it was when laid down but probably not by much.
Stoer Group basal breccia lying on Lewisian. The contact may be steeper than it was when laid down but probably not by much.

We went from the bottom of the Stoer to something a bit higher in the succession but passed a lovely Heilan Coo on the way.

Highland Cow

What we were going to see was the earliest signs of life so far discovered in the British Isles! Admittedly the signs are not very spectacular but they are there!

They are the remains of cyanobacteria (which used to be known a blue-green algae) which enjoyed life as scum on a pond, occasionally sinking to the bottom and forming the structures we see below.

Stromatolites in the Stoer Group, Clachtoll.

Our final stop for the day was on the coast, near Stoer village to look at the Stac Fada formation.

The latest interpretation for this formation is that it is an impactite – a rock formed from the debris of a meteorite impact. If you believe THIS REPORT the meteorite struck the earth near Lairg. And if you believe THIS REPORT it impacted in the Minch

The Stac Fada formation. Note the glassy green fragments.
WEGA on the Stac Fada member.
The Stac Fada formation forms the long spit with the islet near its tip.

We then headed back to Ullapool to prepare for our next excursion.

But we had a view of Suilven on our way back to the van.

View of Suilven from Stac Fada.