Black Rock Limestone at Rhossili

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.