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Crags of the corrie backwall Complex moraine systems at Enegars
Section A 1. 10 m clast-dominated to clast supported,
poorly sorted angular to sub-angular cobble to boulder
gravel. Near its base there are clasts of bedded sands and
laminated clays 2. 1-6 m stratified, medium, well-sorted sands
with, near the top, laminated clays 3. 1-5 m brown, matrix-supported, clast-rich
diamicton. base not seen. Section B (illustrated) 1. 1 m silty fine sand with occasional small
gravel. 2. 3 m very bouldery, clast-supported, poorly
sorted, angular to sub-angular gravel. 3. 8 m reddish-brown,
sandy matrix-supported
clast-rich diamicton. 4. 2-3 m beds of brown, matrix-supported diamicton
interbedded with stratified sands and laminated clays. 5. 1.5-2 m sandy, matrix-dominated diamicton with
cobble- to boulder-sized clasts. The clast lithologies are
dominantly sandstone but there is a significant component of
volcanic rock fragments. A proportion of the clasts are weathered. 6. weathered ashy sandstone bedrock. Section C 1. 12 m brown, sandy diamicton 2. 3 m grey-brown diamicton with frequent
volcanic rock fragments. North Hoy viewed from the N on Google Earth Enegars is the hollow on the far right
(west) of the image. The valleys of north Hoy lead in the
background towards Rackwick Bay |
Enegars CorrieSignificance: a superb corrie formed at an unusually low elevation that was last occupied by a small glacier only 11,000 years ago Enegars scallops the north side of Cuilags and faces almost due north. At its highest point the backwall is about 335 m high. The floor of the corrie is at about 100-120 m OD, an unusually low elevation for a corrie in Scotland. The lip of the corrie has probably retreated due to a combination of ice sheet and marine erosion and now falls sheer to the sea along the impressive sea cliffs that flank this part of of Hoy. Enegars may once have had an adjacent corrie to the west that has been lost to marine erosion. In the grandeur of its sandstone crags, Enegars is matched only by the Applecross corries developed in Torridonian sandstone.
Several moraine ridges lie within the corrie (Sutherland, 1993) which may relate to both a corrie glacier and a lobe of the last ice sheet flowing out of Scapa Flow. A lateral moraine (CLM1) from a former corrie glacier descends the SE side of the corrie for over 300 m. The largest moraine (LLM1) crosses the corrie lip at around 100 m OD and is up to 6 m high on its seaward margin and between 1 and 3 m high on the landward side. The moraine carries a scatter of sandstone boulders that are up to 2 m long and on which weathering pits up to 8 cm deep can be seen. Another arcuate moraine (LLM2) about 150 m long occurs on the SE slope inside the main one.
The poorly sorted, coarse to very coarse gravels at or just below the surface in Sections A and B are considered by Sutherland to be the sediments that comprise the moraine ridges. The stratified sands and clays that immediately underlie these sediments in Section A are water lain and may relate to ponding at the margin of an ice lobe during ice sheet deglaciation. The upper till at C, the two units overlying the basal till at B and the bottom till at A all resemble other tills observed in the north of Hoy. The presence of erratics of volcanic rocks shows that these tills were deposited the last ice sheet. Sutherland (1991, 1993) suggested that the most likely age of the corrie glacier advance was during the Loch Lomond Stadial when other minor glaciers reoccupied corries elsewhere in the Highlands and Islands. This has been confirmed by recent reports of cosmogenic exposure ages (Ballantyne et al., in press).
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