Abstract
IN describing the limestones in the Gwna group of the Precambrian Bedded Succession of Anglesey, Greenly1 distinguished the Simple or “Cemaes” type from the Complex or “Llanddwyn” type. The Simple type is well exposed in a series of tectonically separated masses in the area east of Cemaes Bay (British National Grid map reference SH370940), within many of which a range of limestone varieties occur. These can be studied easily in the limestone mass forming the coastal headland north-west of Penrhyn-mawr (map reference SH37429397), which displays most of the varieties to be found in the Cemaes Bay area in easily accessible cliff exposures supplemented by sections in the walls of the now disused Gadlys quarry (map reference SH37359405). Greenly reported oolitic structure to be “not uncommon” in the Simple type of Gwna limestone, stating that it “is highly developed at Cemaes Bay where the rock is, locally, a true pisolite”. He also described a fine parallel bedding which “can sometimes be seen on the margins of the massive rock” and referred to some of the rocks as “laminated limestones”.
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References
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WOOD, M., NICHOLLS, G. Precambrian Stromatolitic Limestones from Northern Anglesey. Nature Physical Science 241, 65 (1973). https://doi.org/10.1038/physci241065a0
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DOI: https://doi.org/10.1038/physci241065a0