Drumhollistan
Significance: a site on the north coast with thick till sequences enveloping geos and cliffs.
Drumhollistan
Significance: a site on the north coast with thick
till sequences enveloping geos and cliffs.

Drumhollistan

Significance: a site on the north coast with thick till sequences enveloping geos and cliffs

This important site has been described by Omand (1973) who summarises the stratigraphy as:

4. Periglacial slope deposits 1 m thick

3. Brown sandy till, with shell fragments near its base. Up to 21 m thick.

2. Sand and gravel, with some sub-rounded boulders. Up to 3.5 m thick and locally calcite-cemented.

1. Grey till. More than 3 m thick.

The lower till contains stones of migmatite and gneiss, derived from the south and west. The upper till is dominated by Devonian debris and probably derives from the SE. Its reported shell content marks it as the westernmost representative of the shelly till.

Gordon (1993) points out intriguing questions that remain about this site:

A. What are the ages of the tills?

B. What is the significance of the sand and gravel? – this site is unusual in having an intervening layer between the inland and shelly till units. The sand and gravel could relate to melt out of glacier ice, meaning that the two tills are of broadly similar age. Alternatively, the sand and gravel could mark a period of ice retreat from this area prior to the arrival of the shelly till ice.

Calcite-cemented gravel on the western flank of the gulley
The upper till, with abundant ORS debris

We can add:

C. How many different stratigraphic units are present in these thick sequences?

D. How does the upper till relate to the moraines found on the cliff tops and just inland?

E. How old are the coastal landforms – cliffs and geos – which lie buried beneath this substantial accumulation of glacial deposits?

A section in a moraine ridge ~1 km inland. Thin layers of red diamict occur intermittently in the uppermost part of the deposit

Drumhollistan – thick sequences of till left by the last ice sheet moving over the north coast

Key geomorphological sites