Difference between revisions of "Italian Chapel, Lamb Holm to Hoxa, Orkney – an excursion"
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Latest revision as of 09:15, 13 November 2015
From: Fannin, Nigel G.T. Edinburgh Geological Society field excursion Orkney May 1991 (unpublished)
- 1 Locality 1 Italian Chapel, Lamb Holm (HY488 086)
- 2 Locality 2 Echnaloch, Burray (ND 475 966)
- 3 Locality 3 Burray Links (ND 486 974)
- 4 Locality 4 Ayre Of Cara (ND 478 952)
- 5 Locality 5 Barthwick (ND 434 865) to The Kist (ND 434 870)
- 6 Locality 6 Ossi Taing (ND 463 865) to Wind Wick (ND 457 870)
- 7 Locality 7 Sand Wick (ND 428 892)
- 8 Locality 8 Hoxa (ND 421 942)
Locality 1 Italian Chapel, Lamb Holm (HY488 086)
The Chapel was built from a Nissen hut by Italian POW's during the Second World War.
Locality 2 Echnaloch, Burray (ND 475 966)
This is an excellent example of a bay-head ayre which has closed the inner portion of Echnaloch Bay impounding a freshwater loch (oyce).
Locality 3 Burray Links (ND 486 974)
The links are formed of a well developed dune system which includes dune ridges, slacks, machair, sand hillocks and linear blow outs.
Locality 4 Ayre Of Cara (ND 478 952)
This stretch of the Churchill Barrier is of particular geomorphological interest, as it demonstrates the considerable rate of beach accretion since the barrier was constructed in 1942, when the tidal current between the islands was halted. A sandy beach now stretches for 500 m along the east side of the barrier and a large sand bank is forming offshore. The black carbonaceous siltstones of Eday Flagstone age, exposed at the Ayre of Cara contain some complex injection structures.
Locality 5 Barthwick (ND 434 865) to The Kist (ND 434 870)
At Barthwick a small, but spectacular vertical vent of sediment-breccia cuts the Rousay-Eday Transition Beds. It consits of angular, locally flow-aligned blocks of flagstone and sandstone up to 1.3m in diameter,
set in a matrix composed entirely of comminuted carbonate-rich sediment. 340m further north a poorly exposed plug of agglomerate contains many rounded to sub-rounded monchiquite clasts in a matrix composed largely of carbonate. Rhythmic sequences within the Transition Beds will be studied along this coast.
Locality 6 Ossi Taing (ND 463 865) to Wind Wick (ND 457 870)
A continuous section of Lower Eday Sandstone and Eday Flags is exposed. The Lower Eday Sandstone is of the medium-grained cross-bedded facies, with mud-flake breccias at the base of many units. Exposed bedding surfaces show parting-lineations and there are some aligned flute-casts.
Locality 7 Sand Wick (ND 428 892)
The cliffs along the north shore are composed of Middle Eday Sandstone, which is here a massive, bright red sandstone, devoid of pebbles, and with only rare green and red siltstone partings. Cross bedding is relatively rare, but slumping and convolution are common.
Locality 8 Hoxa (ND 421 942)
Camptonite dykes along this shore section are crowded with phenocrysts of augite and hornblende , some up to 12.5 mm in diameter.
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