Barmouth Hillside

Also within

Gwynedd County

Geology & landscape

Geological Period: Cambrian

Birds & fish recorded

Birds

Description

Description A nationally important geological site which exposes an almost continuous rock section from the upper part of the Rhinog Grits, through the Hafotty Formation (Manganese Group), Barmouth Grit and into the Gamlan Formation, all belonging to the Harlech Grits Group of probably upper Comley Series -lower St. David's Series (Lower-Middle Cambrian) age. The locality is of interest for its clear demonstration of the thick clastic sequence, but which also includes the chemically precipitated manganese beds, which appear to allow a general correlation with the St. Tudwal's area and Newfoundland. Many horizons are rich in sedimentary structures (convoluted bedding, grading, flow-marks, groove casts, load casts), and trace fossils also occur. About one third of the site is occupied by woodland. On an exposed, west-facing slope this sessile oak Quercus petraea dominated wood is severely wind-stunted, much of the canopy being only 3-7 m high. In the acidic and well drained parts of the wood, oak is accompanied by downy birch Betula pubescens and hazel Corylus avellana with species such as wood sage Teucrium scorodonia and bluebell Hyacinthoides non-scripta in the ground flora. Localised nutrient enrichment due to the presence of manganese shales results in a more lush flora including ramsons Allium ursinum and cuckoo-pint Arum maculatum with ash Fraxinus excelsior often abundant. The woodland has a varied breeding mammal and bird population; lesser spotted woodpecker is recorded. Wood ants also occur. Remarks: Within the Snowdonia National Park.

Species mentioned