Last weekend we (Emma, John and I) drove down the coast to get out and about and see some geology. The weather was fantastic (as my scorched red, peeling neck will testify), and we got to have some fun running around on beaches.
Location 1 – 55°5.18′ N 5°0.992′ W: Pillow Lavas approximately 1.5km down coast from Ballantrae.
Our first stop of the day was the furthest down the coast, away past Ballantrae. Here we parked at a graveyard and walked down through a farm with some incredibly scary cows which chased us halfway to the ocean. A short walk along the coast brought us to this:
Pillow Lavas!
A great big outcrop of pillow lavas! Not only that, but beneath our feet was an eroded surface which displayed a sectioned mass of pillows with their way-up obviously visible.
Pillow Lavas with Hammer for Scale
Other parts of the outcrop showed overturned pillows where the iron rich minerals of the basalt had been oxidised by the seawater:
Oxidised Overturned Pillows
These pillow lavas were originally deposited in the Iapetus Ocean and then obducted onto the land during the Caledonian Orogeny when the Iapetus closed at somewhere around 440-420Ma. This ophiolite is (somewhat unsurprisingly) known as the Ballantrae Complex and also includes Black Shales, Cherts, Gabbros, minor Granitoids, Serpentinite and some metamorphic rocks (Lawson et al. 1992).
Location 2 – 55° 9.82′ N 4° 56.877′ W: Varyag Monument, Lunch and Boulders.
We stopped for lunch further up the coast just shy of Lendalfoot, at the Monument to a Russian Cruiser which the Russians lost to the Japanese, took back, then got nicked by us, sold to Germany and which we then accidentally sunk in the Firth of Clyde (you can’t make this shit up!). Disrespectfully we posed for photos on the anchor.
Varyag Anchor - John and Emma
After lunch we had a nosey around on the beach to see if we could find anything exciting. The first thing we spotted was this boulder (or possibly outcrop, rather difficult to tell as it was partially buried):
Boulder
Looking closely you can see that this boulder is of mixed composition, with a finely grained rock on the top half, and a coarser grained intrusion at the bottom of the picture. You can even see the coarser grained forcing its way into a crack in the finer grained material, halfway to making a little xenolith. A third composition, even coarser grained also appears to be intruding at the bottom of the image.
We also found an interesting looking greenish boulder which Emma took back to the department and chopped up, revealing what we think is a hydrothermally altered Harzburgite:
Harzburgite (on 1cm graph paper for scale)
Also at this location we found veins of fibrous Pectolite, which I don’t have a photo of to hand, because Emma has the sample.
Location 3 – 55° 9.830′ N 4° 56.62′ W: Boathouse and Dykes. A short walk up the Coast.
Location 3 was slightly along the coast, by an old boathouse. This boathouse was propped up against a nice big dyke. This dyke also displayed an interesting mixed composition; with two distinct compositions in contact with each other. In places small dykes spread off from the main mass, the cross-cutting relationship indicating the order of the intrusions:
Mini-Dyke! (close examination shows chilled margins).
Location 4 - 55° 13′ N 4° 52′ W (Location Approximate): Walk Down coast from Car Park at South Edge of Girvan (next to old folks’ home).
Supposedly there are fossiliferous beds in this area which contain Trilobites, Brachiopods and Graptolites. We couldn’t find any of them. We did however find some excellent examples of various sedimentary and structural features:
Soft Sediment Deformation
Foreground: Faulting. Background: Folding. Emma's Pockets: Stuffed with Rocks
Emma and John (spot the desiccation cracks!)
With that we headed back up the coast to the car, stopping off to collect one more rock sample:
Granite
A nice chunk of Granite that I hammered off of a dyke (albeit a man made one. OK fine, I ‘borrowed’ it from the wall of a field).
With that, we headed back up the coast, stopping off at Troon to continue our field trip tradition of getting Fish and Chips for tea on the way home.
Tags: Ayrshire, Geology, Ordovician, Silurian