Garron Point – Sandend Bay West and East – Portsoy West. Day 3. Excursion to the Banffshire Coast

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Unpublished report prepared for the Edinburgh Geological Society Excursion to the Banffshire Coast. 14th – 21st May, 2005. Leaders: John Mendum, Douglas Fettes, David Stephenson and David Gould (British Geological Survey)

Sandend West [NJ 556 666]

(Figures 23, 24, 25, 26; Plates 10, 11)

Drive to northwest end of village and park. Walk northwestwards across shore section and along a narrow path and over outcrops to near Garron Point. The first part is in calcareous semipelites and metalimestones of the Sandend Harbour Limestone Member (Mortlach Graphitic Schist Formation) and towards the base of this unit are prominent white limestones interbedded with dark grey to black, schistose graphitic pelite with abundant pyrite. This unit passes with brief transition into pale and mid green-grey, calcareous, micaceous psammites and semipelites of the Garron Point Tremolitic Flag Member (Cairnfield Calcareous Flag Formation). Tremolitic schists with garbenschiefer are seen on small crags. This represents a major change in sedimentation at the junction of the Lochaber and Ballachulish subgroups. In suitable lithologies in the Sandend Harbour Limestone Member tight folds and linear fabrics are seen. On returning to the vehicles we will walk to the east side of the harbour and down the rocky shore adjacent to the village. Metalimestone and semipelite-pelite units show open and tight folding and two phases of folding can be recognised.

Sandend East [NC 560 660]

(Figures 25, 26)

Drive to Glenglassaugh distillery and park at back between new and old buildings. Walk round old building and take the good path down to the shore. Devonian conglomerate is seen by the track. The shore exposes metalimestones and semipelites of the Fordyce Limestone Formation (Blair Atholl Subgroup). Tight folds are common with some fold interference structures. The section lies close to the Devonian unconformity and patches of breccia and conglomerate are common. In one instance a large pothole is infilled with Devonian material. By the cliff path grey silts of the Kirk Burn Silt Formation are exposed. The silts were deposited in a proglacial lake adjacent to the coast.

Portsoy West - St John’s Well [NJ 579 668]

(Figures 27, 28)

Drive to swimming pool around back of Campbell Hospital. Park in the open space at the top of the cliffs. Walk along the cliff top to the west and descend cliff path to St John’s Well. Examine contact between the near vertical and strongly lineated and tightly folded psammites and quartzites (Durn Hill Quartzite) and the overlying and graphitic schistose pelites and semipelites. This locality spans the contact of the Durn Hill Quartzite Formation (Islay Subgroup) and Castle Point Pelite Formation (Easdale Subgroup). It also marks the start of the Portsoy Shear Zone, although deformation is high in the top part of the Durn Hill Quartzite. Polyphase deformation is readily seen in the politic rocks.

Selected bibliography

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