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

3.1. ENVIRONMENT CHAPTER 3. SITES ASSESSMENT
outlets for other streams rising on the inner slopes of the ridge of hills occur through the
Binsgarth valley to Finstown, and by the way of the Lochs of Hundland and Boardhouse
to the sea at Birsay.’ (Wilson et al. 1935, 43)
’From the Bridge of Waith to the head of the valley above Finstown the ground rises
gently to a height of about 110 ft. in a distance of about 4 miles and then falls away
rapidly to soar level in a little over three–quarters of a mile. The present stream is only
small and cannot in any way be responsible for the erosion of the Finstown valley.
It rises in Syra Dale, flows southwards and along the foot of the hills to the Loch of
Wasdale and then turns east to Finstown, The streams that flow down the outer side of the
range of hills are ususally short and rapid and tend to run dry in fine weather. The more
important are those that feed the Loch of Swannay, the Burn of Woodwick, the Burn
of Sweenaley and the burns that empty into the Loch of Kirbister,’ (Wilson et al. 1935, 44)
3.1.2 Bathimetry
It had been suggested that a landbridge once existed but there is no bathimetrical evidence
unless historical shorelines were below todays by more than 70 m (s. Fig. 3.1). There
might have been a connection to Scandinavia and Scotland during glaciation, though (s.
Section 3.4).
Concerning lost islands of the North Sea that might have been exposed during the
Mesolithic, the Miocene volcanism in the central North Sea could explain certain simple
spikes in echo sounder traverses (Fig. 3.2).
Looking at magnetic and gravimetric anomalies, one finds associated shallow topography
W of Orkney (Fig. 3.3).
3.1.3 Geology
The Orkney Islands comprise some 376 square miles, are located N of Caithness,
Scotland and there are 90 islands counted, 28 of which are inhabited. The ground
is mostly low–lying (except for Hoy) and the hill girdle seldom exceeds 200 ft. (W
Mainland). Most of the coastline is precipitous and on the western seaboard is formed by
vertical cliffs, often exceeding 100 ft. The beds are often folded into gentle anticlines and
synclines with axes trending between NNW and NNE.
The Granite–Schist Complex is found in the vicinity of Stromness, near Yesnaby and
Graemsay with the Middle Old Sandstone laid on top.
The Lower Stromness Flags are basal breccias, conglomerates and sandstones and
purely local deposits. When traced away from the old land surface on which they rest,
they pass laterally into the normal flagstones of the group. They comprise of blue, grey
and ochreous–weathering beds with occurences of calcareous sandstone that is limy in
character and some yield fragmentary fish remains (Wilson and Knox 1936, 271-2).
The Sandwick Fish–Bed is a well–bedded flagstone that is dark, limy and contains over
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