Examples of Awesome, Unexpected Beauty in Nature

[exchemist]

Observed on my recent trip to Scotland:

[sethoflagos]

1 hour ago, exchemist said:

Observed on my recent trip to Scotland:

Spectacular stuff! Where is it?

Coincidentally, I've just been watching a bunch of YT videos on shear zones on Rob Butler's channel. They go pretty deep while still remaining approachable to the interested layperson.

[exchemist]

Just now, sethoflagos said:

Spectacular stuff! Where is it?

Coincidentally, I've just been watching a bunch of YT videos on shear zones on Rob Butler's channel. They go pretty deep while still remaining approachable to the interested layperson.

On the beach at Cove, Argyll, on the Rosneath peninsula, opposite the Knockderry House Hotel where I was staying. It’s some sort of metamorphic rock, heavily folded and then sculpted into smooth wavy shapes by the sea. Could be a Dunoon phyllite or something, I suppose, but I’m not a geologist so I’m guessing. It’s about 2km back from the Highland boundary fault, on the Highland side. There are a few limpets for scale.
 

It has a rather pleasing blue-grey colour, I find,  shading greenish in the foreground. In fact I was thinking I might blow it up as a print and frame it to hang on the wall as a piece of soothing abstract art. I used to play on these beaches as a small boy, so rocks like this bring back memories for me as well.

[sethoflagos]

2 hours ago, exchemist said:

Could be a Dunoon phyllite or something, I suppose, but I’m not a geologist so I’m guessing.

Looks to be a higher grade of metamorphism than phyllite I think, but it's had knocking on a billion years of pretty tortuous goings on and is wearing its age and experience perfectly. No problem in enjoying it simply for what it is.

 

[exchemist]

5 hours ago, sethoflagos said:

Looks to be a higher grade of metamorphism than phyllite I think, but it's had knocking on a billion years of pretty tortuous goings on and is wearing its age and experience perfectly. No problem in enjoying it simply for what it is.

 

Yes you may be right, now that I have read more about the description of Dunoon phyllite and seen pictures. The grey-blue, smoothly eroded rock in the picture occurs in places along the beach, but most of the rocks are much rougher, darker in colour and have a slatey cleavage. From its undulating smoothness, the rock in the picture appears to be eroded more readily, as if the waves have partially dissolved it. I’d love to know what it is. But I would probably need to speak to a geologist with local knowledge.

[sethoflagos]

4 hours ago, exchemist said:

Yes you may be right, now that I have read more about the description of Dunoon phyllite and seen pictures. The grey-blue, smoothly eroded rock in the picture occurs in places along the beach, but most of the rocks are much rougher, darker in colour and have a slatey cleavage. From its undulating smoothness, the rock in the picture appears to be eroded more readily, as if the waves have partially dissolved it. I’d love to know what it is. But I would probably need to speak to a geologist with local knowledge.

Shouldn't speculate really, but the first thought that came to mind was amphibolite. Similar tones, textures, banding, and definitely not out of place for that area.

[studiot]

I am not familiar with that area but here are a couple of references.

 

http://www.spanglefish.com/northclydearchaeologicalsociety/documents/the-beach-copy.pdf

 

 

Also chapter 6 of this report

 

https://thelochsidepress.com/wp-content/uploads/2023/08/Rosneath-Peninsula-West-Community-Development-Trust-FINAL-REPORT1.0.pdf

Edited September 9 by studiot

[exchemist]

12 hours ago, studiot said:

I am not familiar with that area but here are a couple of references.

 

http://www.spanglefish.com/northclydearchaeologicalsociety/documents/the-beach-copy.pdf

 

 

Also chapter 6 of this report

 

https://thelochsidepress.com/wp-content/uploads/2023/08/Rosneath-Peninsula-West-Community-Development-Trust-FINAL-REPORT1.0.pdf

Yup that's the place all right. Unfortunately neither reference sheds much light on the rocks on the beach at Cove. Cove is further round the coast to the west from the main subject of the first reference, which is chiefly  about a beach walk in the area around Portkil, which is just - by a few hundred metres - on the SE side of the Highland Boundary Fault and thus has geology dominated by Old Red Sandstone. (In fact the map provided of the peninsula shows quite clearly the diagonal valley that marks the fault.) I was intrigued to see the spelling of some names by this writer.  He refers to the Gare Loch as Gairloch, which how is a village far to the north, north of Skye, is spelt. Also he refers to Gallow Hill, on the SE side of the fault, as Gala Law Hill.

Although he and his bevy of charming girls (grand daughters?) evidently walked round as far as Coulport in Loch Long (which is where you have to stop, at the Dr. No. style prohibited area where the UK's nuclear missile warheads are stored!), and therefore must have passed the location where I took my photo, he does not comment on the geology of the rocks in any detail.    

But there is one great photo in the reference, which seems to show the actual fault boundary: a crack with sandstone to the left and schist or gneiss on the right. So that must have been taken on the eastern side of the peninsula - a place I have never walked.

 

[joigus]

Seems like the water is battering on that rock. Is that correct? Beautiful picture, by the way.

Oh, I see you already said it.

[exchemist]

25 minutes ago, joigus said:

Seems like the water is battering on that rock. Is that correct? Beautiful picture, by the way.

Oh, I see you already said it.

Yes, eroded by the waves of the Firth of Clyde. It's below the high tide mark, as indicated by the limpets. 

[sethoflagos]

3 hours ago, exchemist said:

Yup that's the place all right. Unfortunately neither reference sheds much light on the rocks on the beach at Cove

You might be able to glean a little more from Geology of the Greenock district Memoir for 1:50 000 geological sheet 30W and part of sheet 29E (Scotland).

Quote

The north-western part of the district is crossed by the Highland Boundary Fault-system, a zone of fractures along a major tectonic lineament which forms the north-western margin of the Midland Valley of Scotland and juxtaposes metamorphic rocks of the Highlands against younger sedimentary and volcanic rocks to the south. The differential resistance of these various rocks to erosion is clearly reflected in the nature of the topography. The craggy hills of schist and cleaved greywacke which rise steeply from the ice-scoured fiords of Loch Long and the Gare Loch in the northwest part of the district are typical of the south-west Highlands....

 

Dalradian Supergroup

The Dalradian rocks in the district, consisting mainly of phyllites and cleaved greywackes, belong to the Southern Highland Group and are thought to be of late Precambrian age. Three formations have been recognised, the Dunoon Phyllite, the Beinn Bheula Schist and the Bullrock Greywacke, of which the Dunoon Phyllite appears to be the oldest. The Bullrock Greywacke is probably laterally equivalent to part of the Beinn Bheula Schist.

The rocks are mostly of sedimentary origin and were originally composed of muds, poorly sorted sands and fine-grained gravels, considered to have been laid down within a submarine fan complex. The rocks were affected by strong earth movements during the Caledonian Orogeny over a period extending from c.600 Ma to 440 Ma (p.36). They were folded, cleaved and metamorphosed and in this district they are now mainly steeply inclined.

Dunoon Phyllite

The Dunoon Phyllite consists of blue-grey and greenish grey phyllites, black phyllites with lenticular limestone bands, cleaved greywackes and minor fine-grained conglomerates. Most of the greywackes are medium- to coarse-grained sandy units but some are pebbly. The formation is best-exposed along the coast near Cove [NS 221 813] and there are also good exposures in Aldownick Glen [NS 270 850].

On the coast north of Cove, a change from blue-grey phyllites to greenish grey cleaved siltstones marks the contact of the Dunoon Phyllite with the Beinn Bheula Schist. The contact can readily be traced eastwards across the Rosneath peninsula, being offset in places by apparently sinistral movements on north-north-east-trending faults. On the east side of the Gare Loch, the phyllites do not extend as far north as shown on Geological Sheet 29, and the northern limit of the Dunoon Phyllite is now drawn through Croy [NS 260 855]. The southern boundary of the formation is taken at a rapid transition from dark phyllites with limestone lenses to a sequence of coarse, pebbly greywackes, assigned to the Bullrock Greywacke. The contact zone is seen only in Aldownick Glen [NS 270 850].

Greywackes in the Dunoon Phyllite are mainly confined to the southern part of the outcrop and usually occur as separate, graded beds. Load-cast and washout structures are common and the coarser beds in many cases carry siltstone intraclasts in their basal part. Channel bedforms with trough cross-bedding are seen at several places on the coast, for example at a locality [NS 2235 8085] near Barons Point. The pebbly greywackes contain only minor amounts of potash feldspar granules, a feature which distinguishes them from the pink-tinged, more feldspathic pebbly greywackes of the Bullrock Greywacke.

Beinn Bheula Schist

The predominant lithologies in the Beinn Bheula Schist are greenish grey cleaved greywacke and green cleaved siltstone. Generally the greywackes are fine to medium grained in the southern part of the outcrop, near the contact with the Dunoon Phyllite, but farther north they are commonly pebbly, for example in roadside exposures near the north end of Faslane Port. The pebbles are of quartz and feldspar, with a notable proportion of microcline.

Exposures along the coast, at Cove Bay, provide some of the best examples of original sedimentary structures in the Dalradian rocks of the district. The greywacke tends to occur as discrete beds showing Bouma sequences. Repeated grading and ripple-lamination are commonly seen. Calcareous lenses found locally in the greywackes probably formed during diagenesis.

Some beds within the Beinn Bheula Schist are highly chloritic, dark olive-green in colour and have a characteristic massive appearance. These 'green beds' are particularly associated with bodies of metabasite, which occur at Blair-more [NS 195 823] and Knockderry [NS 217 833]. The metabasites are cleaved compact rocks, now composed of actinolite, chlorite, plagioclase and sphene. Some bodies up to 3 m thick, possibly intrusions, clearly show relict igneous textures; others have variable grain size, appear laminated and may be of extrusive origin.

Bullrock Greywacke

The Bullrock Greywacke consists mainly of pink-weathering cleaved feldspathic pebbly greywacke, interbedded with green cleaved siltstone. East of the Gare Loch, black slates with dark grey limestones and blue slates also occur and locally form discrete mappable zones. Formerly the rocks in these zones were ascribed to what is now known as the Highland Boundary Complex, but as they are transitional with typical Bullrock Greywacke lithologies and are enclosed within them, they are now included within the Bullrock Greywacke. Farther south-west in Cowal, black slates and limestones within the Bullrock Greywacke outcrop are placed in a separate lithostratigraphical unit, the Innellan Group.

The Bullrock Greywacke is well exposed on the foreshore from Cove to Kilcreggan, on the hills above Rhu and on both sides of Glen Fruin. The greywackes characteristically occur in amalgamated sequences and do not always show grading. Load-structures and ripple-lamination are seen at some localities. The black slates and limestones are very similar to those within the Dunoon Phyllite. The limestones are recrystallised and occur as lenses about 0.1 m thick.

Conditions of deposition

The sedimentary character of must of the Dalradian rocks is consistent with deposition in submarine fans by turbidity currents and mass flow. In terms of the models proposed for submarine fans by Middleton and Hampton (1973) and Mutti and Ricci-Lucchi (1972), it is inferred that the Bullrock Greywacke was laid down in an inner- or mid-fan environment. The portion of the Beinn Bheula Schist which is present in the Greenock district may have been deposited on the outermost parts of a fan. The Dunoon Phyllite appears to have been laid down in a more distal situation, perhaps in an interfan environment.

Structure

The Dalradian rocks lie within the. Tay Nappe, a major recumbent Fl structure which dominates die Southern Highlands. The limbs of the nappe arc generally flat-lying and the structure faces to the south-east. Its hinge-zone, known as the Aberfoyle Anticline, lies within the Greenock district. A later phase of deformation has 'down-bent' the hinge-zone relative to the horizontal limbs, so that the Aberfoyle Anticline is now synformal and lies within a 'steep belt' in which the bedding and cleavages generally dip steeply inwards the south-east. This steep belt, is some 10 km wide immediately north-west of the Highland Border and includes all the Dalradian rocks of the Greenock district.

Because of the present attitude of the Aberfoyle Anticline, strata on its north-west limb are generally inverted whereas beds on the south-east limb are mainly the right way up. Cleavages are generally downward-facing, that is, the beds become younger down dip on the cleavage planes. An overall change in younging direction takes place close to the southeast margin of the Dunoon Phyllite, inverted beds predominating to the north-west and right-way-up strata being more usual to the south-east. It is considered that the southeast margin of the Dunoon Phyllite is formed by an early slide which disrupts the hinge-zone of the Aberfoyle Anticline.

From what I can make out, the beach walk north starting at the Highland Boundary Fault near Kilcreggan will cross:

• 500m of Bullrock Greywacke until junction with School Road
• 2000m of Dunoon Phyllite until just after beach crossing of Dowall Burn in Cove
• 300m of Beinn Bheula Schist to just before Knockderry House Hotel
• 100m of 'metabasalt' before continuation of Beinn Bheula Schist

This last looks to be associated with the Loch Katrine Volcaniclastic Formation situated directly across Loch Long from the hotel, which is dated to Ediacaran Age. 

Since the hotel is built on this formation I'm guessing it's a good candidate for the photograph.

Edited September 10 by sethoflagos

[exchemist]

On 9/10/2024 at 3:37 PM, sethoflagos said:

You might be able to glean a little more from Geology of the Greenock district Memoir for 1:50 000 geological sheet 30W and part of sheet 29E (Scotland).

From what I can make out, the beach walk north starting at the Highland Boundary Fault near Kilcreggan will cross:

• 500m of Bullrock Greywacke until junction with School Road
• 2000m of Dunoon Phyllite until just after beach crossing of Dowall Burn in Cove
• 300m of Beinn Bheula Schist to just before Knockderry House Hotel
• 100m of 'metabasalt' before continuation of Beinn Bheula Schist

This last looks to be associated with the Loch Katrine Volcaniclastic Formation situated directly across Loch Long from the hotel, which is dated to Ediacaran Age. 

Since the hotel is built on this formation I'm guessing it's a good candidate for the photograph.

Well done indeed for digging this out. So it's possible it is after all a metamorphosed igneous rock then! That might more easily explain the flow-like banding, I suppose. (It seems to be called metabasite rather than metabasalt, though).  I'm still intrigued by the light grey colour and its comparative softness/solubility, as suggested by the smooth way it has been eroded by sea, compared to the surrounding rocks on the beach which are darker and rougher. Perhaps the metamorphosis involved alteration by water as well as heat. 

I suspect we've got as far as we can now without a geologist familiar with the area. 

[joigus]

1 hour ago, exchemist said:

I'm still intrigued by the light grey colour and its comparative softness/solubility, as suggested by the smooth way it has been eroded by sea, compared to the surrounding rocks on the beach which are darker and rougher.

Ok, this discussion is well over my head, but the reason I asked whether the rock was constantly affected by water was precisely motivated by the colour.

You seem to rule out the possibility that the greenish colour be due to microscopic mats? I know I'm probably thinking of the obvious. A geologist's pick would settle it, of course.

As to local knowledge, againg probably thinking of the obvious, I always try to get as many information leaflets, brochures and such from the local tourism office. Surprisingly enough, you sometimes find some valuable specifics about the geological history of the area, botanicals, etc.

I'm sure you know all these things and just didn't get the chance to settle this then and there.

[exchemist]

51 minutes ago, joigus said:

Ok, this discussion is well over my head, but the reason I asked whether the rock was constantly affected by water was precisely motivated by the colour.

You seem to rule out the possibility that the greenish colour be due to microscopic mats? I know I'm probably thinking of the obvious. A geologist's pick would settle it, of course.

As to local knowledge, againg probably thinking of the obvious, I always try to get as many information leaflets, brochures and such from the local tourism office. Surprisingly enough, you sometimes find some valuable specifics about the geological history of the area, botanicals, etc.

I'm sure you know all these things and just didn't get the chance to settle this then and there.

I don't rule out microbial mats for the greenish colour in the foreground of the picture. It is the pale, bluish grey colour that I find interesting, as it seems unusual. There is no tourism office on the peninsula, though I suppose there might be in Helensburgh. When I next go back, I might see if Glasgow University has anything, or anyone, to comment on this. The Dalradian Series is pretty famous (if fiendishly complicated) and well-studied, so I'm sure the answer is there somewhere in the geology community.   

[sethoflagos]

4 hours ago, exchemist said:

It seems to be called metabasite rather than metabasalt, though

Metabasite is a broad term for a metamorphosed basic (ie. low silica) rock. If that low silica rock was originally a basalt (as in this particular case) we can be more specific and call it a metabasalt. The terms aren't exactly synonymous, but ...

A lot of these newer terms have appeared due to the modernisation of rock type systematics that the BGS has been implementing over the last couple of decades.

More at BGS Rock Classification Scheme

My crib sheet for metamorphics attached.

2 hours ago, joigus said:

You seem to rule out the possibility that the greenish colour be due to microscopic mats

Most of the outcrops in this area have been subjected to a 'greenschist' grade of metamorphism which is typically characterised by the green mineral chlorite. I'm not 100% sure that @exchemist's blue is the glaucophane blue of 'blueschist' grade, but it's possible. 

Classification of Metamorphic Rocks.pdf

[StringJunky]

[joigus]

8 hours ago, StringJunky said:

Beautiful.

Do you happen to know the species?

[StringJunky]

6 minutes ago, joigus said:

Beautiful.

Do you happen to know the species?

I think it's a Blue Whale if irrc. I pulled it off my FB feed.

Edited September 18 by StringJunky

[joigus]

7 minutes ago, StringJunky said:

I think it's a Blue Whale if irrc. I pulled it off my FB feed.

That's exactly what I thought too. Based on size and proportions and from what I've seen in documentaries...

They look kinda slender, not as bulky as other whale species.

[StringJunky]

4 minutes ago, joigus said:

That's exactly what I thought too. Based on size and proportions and from what I've seen in documentaries...

They look kinda slender, not as bulky as other whale species.

Yes, they are very graceful and torpedo-like. I like that image  because you can see it directly against a human for scale to make you feel really humble. I think of them as the cows of the sea.

[iNow]

1 hour ago, joigus said:

Beautiful.

Do you happen to know the species?

Pretty certain those are homosapiens in the boat

[joigus]

Just now, iNow said:

Pretty certain those are homosapiens in the boat

Are you sure there's not a dog with them?

[iNow]

Just now, joigus said:

Are you sure there's not a dog with them?

Did you mean canis familiaris?   

[joigus]

2 minutes ago, iNow said:

Did you mean canis familiaris?   

More specific even. A common occurrence: Haitians with a Pekingese. Impossible to rule that out.

Edited September 18 by joigus
minor correction

[studiot]

We visited Becky Falls over the weekend, which is largely made of heavily weathered Dartmoor granite.

The white rock at the top of the picture is a good example  -  Dartmoor Granite looks just like weathered and crumbling concrete with a greyish white colour.

The banded black rock is a chunk of hornblende/amphibole with quartz banding which can be found in odd places around the gorge.

The individual drinks carton in the middle is there for scale.

 

I wonder if this has any similarity to @exchemist  strata?