Streetmap extract

Crags of the corrie backwall

Complex moraine systems at Enegars

dwarfie hamars    flaga Loch Lomond Stadial

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 Corrie

Significance: 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.

Stream sections reveal some of the sediments that form the moraines. Section A described by Sutherland (1993) and listed here is beneath the inner part of LLM1 and Section B is seawards of this, close under the outer part of the moraine.  To the east of the corrie at the head of the Bay of Tongue there is a drift ridge that extends from the foot of Lounders Fea to the coast where it is truncated by the marine cliff.  A poorly exposed section at the top of the cliff (HY20650470) has been described by Sutherland (1993) as Section C.

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).