The Nevern Estuary anomaly

One of the big igneous erratics on the foreshore of the Nevern Estuary

https://earthwise.bgs.ac.uk/index.php/Caradoc_Series,_Ordovician,_Wales

"In south-west Wales, extensive dark grey, silty, graptolitic, pyritous mudstone is Caradoc in age, and indicates that relatively deep water and low energy conditions had persisted since late Arenig times. However, in north Pembrokeshire and south Cardiganshire, the sedimentation was influenced by movement on the Newport Sands Fault. South of the fault, sedimentation was mainly of mud, which now comprises the Pen yr Aber and Cwm yr Eglwys mudstone formations. North of the fault, the upper part of the Cwm yr Eglwys Mudstone Formation interdigitates with and is overlain by turbiditic sandstone, mudstone, slumped beds and conglomerate of the Dinas Island Formation (P662414), which is well exposed in the cliff sections between Dinas Head and Poppit Sands."

According to the records, the Penyraber mudstone formation rests more or less conformably or discomformably on the complex rocks of the Llanvirn Fishguard Volcanic Group.  But according tom the geologists there must have been a long time interval between the accumulation of volcanic materials and the accumulation of the deep sea sediments above them.

Anyway, the Penyraber mudstones are typically black or dark grey, and they outcrop in the Nevern estuary  in the north side of the river, inside the sand dunes and along the shore as far as the "iron bridge".   There are no signs of interbedded or underlying volcanic deposits, and I am still pondering on the origins of the cluster of igneous erratics on the foreshore, between the high and low tide marks.  They still remind me o the strange igneous outcrops in Ty Canol Wood, but if the erratics come from there, the ice must have travelled northwards from Mynydd Preseli, and the jury is still out on that one.........

What I noticed yesterday, on one of our estuary walks, was a high concentration of stained quartz fragments, some of them quite angular, littering the beach surface near the Riverslea boat house.  There also seem to be two parallel alignments.  I must go back and examine them when I am not threatened by an incoming tide -- is there an outcrop of something interesting just beneath the beach surface?  Watch this space.......