Hill End to Spaniard Rocks & Back: Step-by-Step Part 7

Walking back from Spaniard Rocks now, I took a route closer to the dunes where the character of the shore is quite different from the wet sand and strandlines between high and low tide levels. Here there are pebbles. Rhossili’s pebbles intrigue me. I love scrambling over the banks of stones at the very top of the beach. The colours are lovely pastel shades with pinks and blues and overall reminding me of sugared almonds. A total delight. Many rock types are represented. Some have interesting patterns.

I like the way that the numbers of beach stones seem to increase or decrease depending on how they are pushed around the shore between one visit and the next, and how the sand changes its level and distribution throughout the year and the transition from season to season. This time the wooden ribs and keel of the shipwrecked ketch Anne were only just visible above the sand and pebbles. I like the way that pebbles are arranged partly buried in the damp sand that quickly dries to a different hue and texture. The pebbles underlie the tall sand dunes of the Llangennith Burrows. The dunes have been scooped out by stormy seas and footsteps in many places to demonstrate that even wind-blown sand is stratified; and marram grass roots exposed to air show how deep they penetrate the soft fine sediments to bind them together and stabilise the dunes.

Beach Stones with Iron at Rhossili

A beach stone made of iron on the Gower Peninsula in South Wales

When you visit a place often enough, you think you have seen all there is to see. For all the photographs of rocks and pebbles that I have taken over the years, I don’t think I had ever noticed so many stones made of iron as I did on my last trip to Rhossili on the Gower Peninsula, South Wales. Mostly they were lying in the narrow strip of pebbles, cobbles, and boulders that is exposed on the upper reaches of the sandy shore, right at the base of Rhossili Down.

Some of these iron stones appear to be made entirely from iron (maybe iron carbonate) while others were sedimentary rock with a solid iron centre, or with groups or bands of small iron nodules. One stone was stratified with black and rust layers. All of them were very heavy and many exhibited concretionary layers. I know very little about these stones. Their forms of iron are distinctly different from the haematite form that I have previously shown in other blog posts about Gower geology, and from the iron pyrites nodules I have featured from Dorset’s Jurassic rocks. Those stones with groups or layers of smaller nodules look like the siderite form of iron that I photographed at Joggins in Nova Scotia. Iron is recorded in Lower Carboniferous rock strata and also in the Coal Measures higher up in the geological sequence, so iron stones on this Gower beach make general sense but they may have been transported there from another location. Clearly more investigation is required.

More pebbles at Rhossili after storms

More pebbles are visible on the beach at Rhossili on the Gower Peninsula since last winter’s storms. Of course, they were always there but not so many on show. Lots were hidden beneath the sand. The greater number of pebbles is noticeable as soon as you arrive at the beach via the path through the dunes from Hillend campsite. Looking north towards Burry Holms, and south towards Worms Head, a wider band of pebbles than usual is immediately noticeable at the top of the shore.

As you walk towards Diles Lake, which is the stream that flows across the shore from Llangennith Marshes, the pebble layer deepens into a wide bank that more or less dams the stream. This place is subject to frequent change as a result of changes in weather, tides, and currents. It can sometimes be difficult to cross, especially in winter. Right now though, crossing is easy because the stream mostly runs beneath the pebbles, with only a narrow watercourse visible on the surface. It is clear that not only are more pebbles around because sand has been washed away from them but also the pebbles have been pushed up the shore with great force.

Rhossili pebbles in a basket

Pebbles with white lines from Rhossili: Assortment of mostly striped pebbles from Rhossili, Gower, South Wales, showing appearance when dry (1)

An assortment of pebbles found on the beach at Rhossili on the Gower Peninsula, showing the significant difference between the appearance of the pebbles when they are wet and when they are dry. This selection of pebbles contains varied rock types but I chose them for display because of their mostly striped markings.

Wet striped pebbles in a basket: Assortment of pebbles, mostly with striped patterns, from Rhossili, Gower, South Wales, showing appearance when wet (2)

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Rhossili pebbles on a plate

Rhossili pebbles: Assortment of pebbles from Rhossili on the Gower Penisula with a common coarse-grained sandy textured, smooth flattened shape, and subtle colours of grey, beige and pink; possibly Millstone Grit from the Upper Carboniferous Period.

A selection of pebbles from Rhossili Beach: rounded but flattened, with a coarse sandy texture, and in subtle shades of grey, beige and pink, displayed on a sea-green glazed plate. I think these might all be derived from Millstone Grit rock which is part of the Carboniferous Period strata which make up the  landward portion of the Gower Peninsula. I am thinking that they could all have been washed around the coastline from their point of origin, or even brought to the tip of the peninsula by the action of the ice sheets that once almost entirely covered Gower.

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Pebbles at Rhossili Part 3

wet pebbles on the beach: Wet multi-coloured pebbles on Rhossili beach, Gower, West Glamorgan, South Wales, UK (11)

Another selection of the marvellously varied pebbles at Rhossili Beach, Gower.

Rhossili pebble: Patterned pebble on Rhossili Beach, Gower, West Glamorgan, South wales, UK (12)

Patterned pebble with ironstone nodule on Rhossili Beach, Gower, West Glamorgan, South Wales, UK (13)

Gower pebble: Yellow and white conglomerate pebble on Rhossili Beach, Gower, West Glamorgan, South Wales, UK (14)

Patterned pebble: Grey limestone pebble with red and yellow markings on Rhossili Beach, Gower, West Glamorgan, South Wales, UK (15)

Red sandstone pebble with grey and rusty bands on Rhossili Beach, Gower, West Glamorgan, South Wales, UK (16)

Striped pebble: Wet grey limestone pebble with white stripes on Rhossili Beach, Gower, West Glamorgan, South Wales, UK (17)

Gower pebble: Wet grey and ochre stripey limestone pebble on Rhossili Beach, Gower, West Glamorgan, South Wales, UK (18)

Patterned Gower pebble: Rusty patterned grey limestone pebble on Rhossili Beach, Gower, West Glamorgan, South Wales, UK (19)

Coloured pebbles on Rhossili Beach: View at Rhossili looking towards Burry Holms, showing bank of multi-coloured pebbles at base of the dune system called Llangennith Burrows, Gower, West Gamorgan, South Wales, UK (20)

 Revision of a post first published 2 March 2010

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Pebbles at Rhossili Part 2

 Pebbles at Rhossili Bay: Rain-spotted multi-coloured pebbles at Rhossili, Gower, West Glamorgan, South Wales, UK (1)

The pebbles that lie at the base of Rhossili Down in Gower, and extend along Rhossili beach at the foot of the sand dunes known as Llangennith Burrows, are amongst the most colourful and varied that I have ever encountered.

They are mainly quite large but not exactly cobble sized. They range in colour from reds and pinks, orange and yellows, to buffs and greys – many blue-greys. The rocks from which they are composed include limestones, sandstones, grits, and conglomerates. Some come from local strata of the Carboniferous and Devonian periods.  Others could possibly originate much further afield and have arrived embedded in massive sheets of ice that once covered most of the Gower Peninsula.

The pebbles range from the smooth and glossy to fine and coarse grained. Occasionally you find ones made up of many smaller chunks and pieces of all types, textures, and hues. The shapes vary from the very irregular to approximately geometric shapes such as circular, spherical, discoid, rectangular, square, and cuboid. Patterns in and on the stones can include stripes, layers, lines, and abstract designs. The pebbles are endlessly interesting and beautiful. These photographs are part of a series showing their immense variability.

The weather was unsettled when I took these pictures; the raindrops of the first shower account for the speckled egg-like appearance of the shots at the top and bottom of the post. After that, the rain came down more steadily and worked in some ways to my advantage by intensifying the colours and imparting a gloss to the surface of the stones.

Red and yellow pebble: A smooth, red and yellow coloured pebble on Rhossili beach, Gower, West Glamorgan, UK (2)

Sandstone pebble: A rounded grainy textured pebble with regular fine brown stripes at Rhossili, Gower, West Glamorgan, South Wales, UK (3)

Patterned pebble: A rounded buff-coloured sandstone pebble with an irregular pattern of rusty rings and patches from Rhossili, Gower, West Glamorgan, South Wales, UK (4)

Pebble with red and yellow yin-yang design: A smooth rounded sandstone pebble, with a red and yellow design looking like the yin-yang symbol, from Rhossili, West Glamorgan, South Wales, UK (5)

A conglomerate pebble with circular outline and incorporating small red, pink, and white chunks of various rocks, at Rhossili, Gower, West Glamorgan, UK (6)

Gower beach pebble: A sandstone pebble with a pattern of concentric lines in shades of pink and orange at Rhossili, West Glamorgan, UK (7)

rain-speckled beach pebbles: A general view of the pebble bank at Rhossili, Gower, West Glamorgan, South Wales, UK showing the multi-coloured stones speckled by rain-drops. (8) 

Revision of a post first published 22 February 2010

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Pebbles at Rhossili Part 1

Pebbles with pastel colours like sugared almonds on the beach at Rhossili Bay, Gower, South Wales, UK (1)

Looking like lots of pastel-coloured sugared almonds, these pebbles from Rhossili Bay reflect not only the immediate solid geology of the area but also the surface geology relating to former glaciation events.

The pale blue-grey smooth stones are Carboniferous Limestone which outcrops in the two headlands of the bay at Worms Head and Burry Holms. The pink and red relatively coarse-grained stones are derived from the Old Red Devonian Sandstone which forms the basis of Rhossili Down at the head of the bay. Other stones of all sorts, originally from places far away, have been delivered to the location as they melted out of the bottom of an ice sheet or glacier over 10,000 years ago.

Pebbles like candy on the beach: Pebbles with pastel colours like sugared almonds on the beach at Rhossili Bay, Gower, South Wales, UK (2)

Revision of a post first published 26 March 2009

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Rhossili pebbles (1)

Rhossili pebbles: Pebble with a pattern on Rhossili Beach, Gower, South Wales, UK (1)

The pebbles on Rhossili beach in Gower are not only attractive objects worthy of attention and interest because of their wonderful variety of colours, shapes, patterns and textures – but also because they are important clues to the geology of the region. I have been fascinated by them for years but I am only slowly getting to understand what they represent. I’m actively challenged in trying to identify the different rock types and origins whilst still admiring and photographing them for their aesthetic qualities.

The pebbles in this post were all photographed on the strip of pebbles exposed at the top of the sandy beach on Rhossili Bay – at the foot of the Rhossili Down solifluction bench to the south, and at the base of the Llangennith dunes to the north.

Their grainy texture makes me think they are all composed of sandstone of some type (with the possible exception of Pebble 4 which is much finer grained like a limestone). The colour is grey or beige. They all have patterns of lines and concentric circles in a darker rusty colour which probably represents staining by iron. The pebble patterns indicate that the rock from which they are formed is made up of layers or strata (sedimentary rock). The way the broken pieces of rock have been rolled around the beach by the waves over thousands of years has worn and weathered them to a smooth, rounded shape at the same time as revealing the delightful patterns.

Working out exactly which bedrock series the pebbles came from is complicated on Rhossili beach. The pebbles may not only have originated in the immediately adjacent land forms – like the headlands of Burry Holms, Worm’s Head, and Rhossili cliffs which are made of Carboniferous limestone; and Rhossili Down which is made of Old Red Devonian sandstone – but also may have been brought around the coast from other parts of the Gower Peninsula where Millstone Grit or Coal Measures are the main bed rocks. In addition to this, ice sheets periodically covered much of Gower in the past (though not as far as Rhossili beach itself) and the ice brought with it rocks from far afield, which were deposited when the ice melted and the ice sheet retreated. So some stones on the beach may be completely foreign to the area and brought around the coast by the tides.

Furthermore, within each of the main locally occurring rock types, there is a series of sub-types which would have been laid down in differing environmental conditions. For example, The Old Red Sandstone in West Gower includes quartz conglomerates, brown-stones, and red marls – which vary enormously in composition and appearance. Millstone Grit apparently consists of a varied and variable group of sandstones, grits and shales from very coarse to very fine in texture.

My best guess, at the moment, is that the pebbles shown in this post are derived from the Millstone Grit sequence…but I am very open to correction if any reader could advise me.

Patterned pebble: Pebble with a pattern on Rhossili Beach, Gower, South Wales, UK (2)

Rhossili pebbles: Pebble with a pattern on Rhossili Beach, Gower, South Wales, UK (3)

Patterns in nature: Pebble with a pattern on Rhossili Beach, Gower, South Wales, UK (4)

Rhossili pebbles: Pebble with a pattern on Rhossili Beach, Gower, South Wales, UK (5)

Rhossili pebbles: Pebble with a pattern on Rhossili Beach, Gower, South Wales, UK (6)

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Sand-covered pebbles at Rhossili

Sand picture: Sand-covered pebbles at Rhossili Bay, Gower, South Wales, UK (P1430216aBlog1)

The dynamics of sediment movement on beaches intrigues me. Every time you visit a favourite beach it looks different. The tides, currents, wind and weather all play a part in the transformations. The structure of the seashore is sometimes hidden and sometimes revealed. Last autumn the pebbles at the foot of the soft red cliffs beneath Rhossili Down on Rhossili Bay in Gower, South Wales, were in the process of being covered up by sand.

The texture and distribution of the sand showed that it had first been a wind-blown accumulation; then had been consolidated by rain; and at that particular moment it was drying out and beginning to crack over the curved surfaces. The images illustrate the contrast in textures and colours between the sand and the pebbles. The surface of the sediment layer mimicks the pebble shapes below. The overall effect is one of softening of the appearance of the pebbles as if they had been covered by a light blanket of drifting snow.

Gower beach picture: Pebbles coated by drifting sand at Rhossili Bay, Gower, South Wales, UK (P1430219aBlog2)

Sand texture photograph: Wind-blown sand covering a pebble bed on Rhossili beach, Gower, South Wales, UK (P1430221aBlog3)

Pebbles and sand picture: Pebbles partially covered by wind-blown sand at Rhossili Bay, Gower, South wales, UK (P1430155aBlog4)

Picture of pebbles and sand: Pebbles from Rhossili Bay, Gower, South Wales, UK, covered with wind-blown sand (P1430159aBlog5)

Rhossili Beach picture: View looking north along Rhossili Beach showing sand-covered pebbles at the base of the soft red cliffs of Rhossili Down (P1430158aBlog6) 

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