Waterland–People: On Structure and Origin of Crannogs ...

3.1. ENVIRONMENT CHAPTER 3. SITES ASSESSMENT
Figure 3.2: Height of spike like features on echo traces in the northern North Sea (Flynn 1973,
52). Some spikes can be seen to the NW of Orkney Mainland and Rousay which could be volcanic
masses.
those in the Upper Old Red Sandstone times and they are sandy and marly bands which
is lithologically identical to material from the Trias (Wilson and Knox 1936, 273).
The Upper Old Red Sandstone in Hoy overlies a sequence of earthmovements, a period
of denundation during which 10 000 ft of strata were removed and Volcanic outbursts
of explosive character with ashes overlay the lands surface along with a 200–300 ft.
thick sheet of basic lava and a slaggy top of 50 ft. It was leyd down after another short
period of denundation and is contemporary to the Dunnet Head Standstones in Caithness.
Occurences vary in pink, red and yellow and are 3500 ft. thick (Wilson and Knox 1936,
273–4).
Over 200 Intrusive Igneous Rock dykes cross Orkney in various parts and directions.
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