Fraserburgh – Inverallochy - Gardenstown – Boggierow Wood. Day 6. Excursion to the Banffshire Coast

From Earthwise
Jump to: navigation, search

Unpublished report prepared for the Edinburgh Geological Society Excursion to the Banffshire Coast. 14th – 21st May, 2005.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)


Inverallochy. [NK 050 648]

(Figures 41, 42, 43; Plates 32)

Park at end of road between shore and Whitelinks golf course. Walk to end of exposure of the rock platform the end of seawall. Rock platform shows nebulites and garnetiferous schollen diatexites with calc-silicate lenses and garnet porphyroblasts (now commonly altered to chlorite). Psammite beds and clasts show pressure solution cleavage. Northwest-trending (324°) ice grooves and glacial striae.

On returning to the parking, drive west to the end of the village, park and examine the psammites on the foreshore immediately below that show well-developed ‘relict’ pressure solution striping.

Cairnbulg [NK 034 655]

(Figures 41, 42, 43; Plates 30, 31)

Drive past harbour to shore west of jetty. Park in open space overlooking the beach.

Proceed by coast path 200 m to southwest. Examine good examples of migmatites, diorite and cross cutting Cairnbulg Granite (Johnson et al, 2001). Complex relationships are well seen. Rarely, lenses of sillimanite-rich pelite can be found.

Kinnairds Head, Fraserburgh [NJ 998 677]

(Figure 41; Plate 29)

Park at the lighthouse museum. Examine the rock section at the top of the foreshore below the foghorn by the lighthouse. Calcareous semipelites, calc-silicate rock and impure metalimestones of the Kinnairds Head ‘group’ (Crinan-Tayvallich Subgroup can be seen. Excellent D3 folds and retrograded andalusite; locally with sillimanite. Vertical face c.15 m northeast of the foghorn shows a classic refolded fold with tight F1 and stepped F3. The metasedimentary rocks are cut by white leucotonalite veins and sheets up to 2 m thick.,

Gardenstown (1) [NJ 803 651]

(Figures 38, 39, 40; Plates 25, 26)

Go to east end of town and park at shore near picnic tables. Walk along shore to The Snook. The basal part of the Mid Devonian Gardenstown Conglomerate Formation is well exposed in the cliff. Its unconformable relationship with the underlying Early Devonian Seatown Sandstone Member of the Pennan Sandstone Formation (Crovie Sandstone Group) can be traced along the shore. In parts small- and medium-scale faults obscure the contact.

Gardenstown (2) [NJ 799 648]

(Figures 38, 39, 40; Plates 25, 27)

Walk or drive to west side of the harbour. A good section is exposed directly below the wall in the Early Devonian West Harbour Sandstone Member of the Pennan Sandstone Formation (Crovie Sandstone Group). Near a concrete block, good ripple marks, cross bedding, convolute bedding and mudclasts are seen. 22m out from centre of the stone jetty wall trace fossils with Beaconichnus (arthropod tracks) are found. Beaconites and good mud cracks can also be found immediately on the foreshore just to the west.

Boggierow Quarry [NJ 575 652]

(Figure 31)

Park at the old lay-by west of Portsoy and walk carefully along the A 98 to enter the wood. The disused quarries show foliated and augened Portsoy granite, now dated at 600 Ma. Semipelitic screens are abundant and xenoliths common. Selected bibliography

At all times follow: The Scottish Access Codeand Code of conduct for geological field work