10 Panorama Walk

This highly popular, short, easy walk may be used as an extension of Excursion 2 to examine the lowest parts of the Mawddach Group and some of the numerous sill-like intrusions which lie within the group. Access to Panorama Walk is from Panorama Hill, which rises steeply from the Barmouth-Dolgellau road [SH 6194 1563] near the railway bridge in Barmouth. It is well sign-posted. The start of the footpath leading to Panorama Walk (Figure 27) crosses a long, straight dry valley of glacial origin.

Locality 1 [SH 6250 1667] The road cutting, not actually on the walk, is worth a visit to examine the typical dark grey to black silty mudstone of the Clogau Formation. The dip is variable, and there is a well-developed cleavage. The Clogau is the lowest carbonaceous formation in the Cambrian succession in North Wales. In places it has yielded many fossils, though none has been found here.

Locality 2 [SH 6254 1650] Exposed on the path and on the knoll to the north are cleaved, flaggy, medium grey, laminated silty mudstone and coarse quartzose siltstone, together with some thicker greywacke beds at the base of the Maentwrog Formation.

The locally flinty appearance of these rocks is the result of contact metamorphism caused by the dolerite intrusion which forms the south-eastern face of the knoll. The sedimentary characteristics of the formation, described in Excursion 3 (p. 24), may be observed in rocks at this and subsequent localities.

Locality 3 From the gate [SH 6268 1655] to the top of Panorama Hill a typical sequence through the lower part of the south-eastward dipping Maentwrog Formation can be examined. Weathering has accentuated the sedimentary structures in the coarse quartzose siltstone and fine sandstone beds, and there are some excellent examples of parallel-, cross- and convolute-lamination and slumping.

A number of dolerite sills, some of which are coarse-grained, intrude the sedimentary rocks, and stand out as more blocky exposures usually with regular, evenly spaced joints.

A small, collapsed trial-working lies to the east of the path [SH 6270 1649]. It is one of several old workings hereabouts, all part of Panorama Mine. The trials in quartz-sulphide veins were first worked in 1887, and from 1900 to 1924 Isaac Storey put a great deal of effort and money into his search for gold in this area. The main adit was driven by him from the east into the hillside below Panorama Walk. It intersected six quartz veins containing chalcopyrite, galena, sphalerite, pyrite and pyrrhotite, but there is no record of gold having been found.

Locality 4 Near the farthest point of the path [SH 6264 1628] is a distinctive hollow, possibly classifiable as a p-form, about 10 m in length, 30 cm deep and with a smooth ribbed surface. It trends north-east (Figure 28) and was possibly carved by boulders entrapped in the ice at the base of the glacier that occupied the valley during the last Ice Age. Near the peak is a large, angular erratic of pebbly greywacke, probably derived from the outcrop of the Barmouth or Rhinog formations in the centre of the Harlech dome.

South-east of the summit [SH 6260 1634] another trial pit has been dug along two quartz veins containing small amounts of galena. From here, most of the formations of the Cambrian succession of the Harlech dome can be picked out. To the north-west the greywackes of the Barmouth Formation form the craggy summit of Garn, and the shales of the Gamlan Formation form the lower grassy slopes. The lowest ground, now followed by the minor road leading to Panorama Walk and Sylfaen, lies in soft mudstones of the Clogau Formation. South-east across the estuary, the Ffestiniog Flags Formation crops out at Penmaenpool and Fegla Fach, while the slate tips farther to the west lie in the Cwmhesgen Formation. Dolerite intrusions form the hills behind the slate workings. Beyond them the Cader Idris range is built of volcanic rocks of Ordovician age.

Along the north-west side of the circuit another small adit along the margin of the dolerite sill can be examined. Near the contact the beds are folded into a small anticline and syncline.

(Figure 56) Slumped beds.

References