Rock textures at Kimmeridge Bay on Dorset’s Jurassic Coast where water runs down the cliff face. Deep orange-red iron deposits on the surface of the grey limestone are revealed by recent rock falls; and granular calcium precipitation coats rock where water falls persistently.
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There are many strange and interesting shapes and textures in the rocks on the beach at Mewslade Bay on the Gower Peninsula in South Wales. Most of them seem to be the result of weathering and erosion but these photographs show something different, unique, for that location. They appear to be preserved (fossilised if you like) ripple marks from the ancient seabed sediments of which the rocks are composed and date very approximately to about 350 million years ago. They have a distinct patterning which is very familiar from the sand and mud of present day seashores in the same area.
The rock itself is High Tor Limestone from the Carboniferous Period. Actually, It’s a bit old fashioned now to say just Carboniferous Period. Everything has changed. To be more accurate, I should say that the High Tor Limestone Formation is part of the Pembroke Limestone Group, which originated in the Visean division of the Dinantian, which in turn is part of the Mississippian sub-division of the Carboniferous Period.
What were at one time horizontal seabed surfaces have become near vertical over many millions of years of earth movements. The now-exposed surfaces of the old bedding planes are revealed in the entrances to caves at Mewslade Bay. The photographs show them encrusted with recent colonies of living acorn barnacles and occasional limpets.
Reference
Howells, M. F. (2007) Wales, British Regional Geology, British Geological Survey, Keysworth, Nottingham, UK, ISBN 978-085272584-9, pp 112 – 125.
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Patterns of iron-stained calcite deposited on the surface of quarried limestone on the Isle of Portland – which is part of the UK’s Jurassic Coast.
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For more information about Sea Belt or Poor Man’s Weatherglass seaweed – Laminaria saccharina (Linnaeus) Lamouroux – see the earlier Postings about this species on Jessica’s Nature Blog.
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In young peacocks when the adult feathers are replacing the dull downy feathers, the colours of the newly sprouted plumage seem different from those in the fully mature bird – having far more yellow and green feathers than the typical predominance of blue that you usually find in the brightly coloured parts of the adult bird. There is a lovely contrast at this stage of development, not only between the hues and patterns of the different parts of the young peacock, but also in the textures between the feathers and the down.
Details of the natural patterns, colours, shapes, and textures in cliff strata at Rhossili Bay on the Gower Peninsula. These rocks belong to the Black Rock Limestone Sub-Group of Carboniferous period strata (Tournasian, Courceyan, Pembroke Limestone Group). They are typically limestones that are dark grey, thin to thick bedded, bioclastic and dolomitic in the upper part.
The black colouration in these close-up images is superficial and created by an encrusting bio-film, probably of black lichen but maybe a cyano-bacterial film. The green colours are caused by a coating of microscopic algae. The bright red, yellow, and orange patches are areas where rock has recently broken off to reveal limestone containing iron compounds. I took these photographs because I found the abstract compositions pleasing – natural geological abstract art.
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These pictures show Caswell Bay (Gower Peninsula) Carboniferous period limestone and mudstone rocks in close-up, showing natural patterns and textures of stratigraphic layering and fracturing, coloured mineral inclusions, acid rain and wave-action weathering, and encrustations by bio-films and marine littoral invertebrates. The rocks include Caswell Bay or Gully Oolite, High Tor Limestone, and Caswell Bay Mudstone.
Click here for more pictures and information on ROCKS
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The boulder-covered shore at Monmouth Beach in Lyme Regis is mostly famous for its fossils like ammonites and petrified wood. The stretch of coastline to which it belongs is a part of the designated World Heritage Site called the Jurassic Coast….but even the boulders themselves are interesting and can show intriguing designs of fractures and cracks that are in some way related to the sediment types, although I don’t know how. Here are some examples, showing first the natural fracture pattern in a close-up shot and then the picture of the boulder on which it was found, in context on the beach.
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