sentences:  Following the end of the last ice age, sea levels rose to roughly their current levels by around 6000 years ago.Forests which had become established at or below this level were destroyed though the preserved stumps of trees in growth position can still be seen in the intertidal zone in places, as can the remains of peat deposits which again had originally formed above the high-water mark.Redistribution of glacial and fluvial sands has given rise to extensive dune systems around the Welsh coast, notably at Newborough Warren on Anglesey, Morfa Harlech and Morfa Dyffryn in Gwynedd and at Pendine and Pembrey Burrows in Carmarthenshire and at Merthyr-mawr Warren and Kenfig Burrows in Glamorgan.