COUNTRYSIDE COUNCIL FOR WALES
SITE OF SPECIAL SCIENTIFIC INTEREST: CITATION
National Grid Reference: SH317734
Site Area: 3.6 ha
This site is selected for its geological interest.
This locality provides an excellent example of small-scale, non-cylindrical folding in an Ordovician greywacke sequence. Minor folds are uncommon in the Lower Palaeozoic rocks of North Wales and the site therefore provides an important locality at which the morphology of minor folds can be compared with that of the major folds. Folds of sandstone units are demonstrably non-cylindrical on a variety of scales. Excellent cleavage fans can be observed in the pelitic units surrounding the folded sandstone layers. The Lower Palaeozoic rocks of Anglesey differ from those elsewhere in North Wales because the underlying basement (the Mona Complex) is visible. Rhosneigr provides a locality at which deformation on a variety of scales in the cover sequence can be examined.
Note: Rhosneigr SSSI is adjacent to, but distinct, from Rhosneigr Reefs SSSI. The latter is selected for its marine biological interest.