On egg-shaped stones dredged from Wick Harbour

Abstract

FROM time to time, rounded, mammillated, and egg-shaped stones have been dredged from the bottom of Wick Harbour, many of which are remarkably symmetrical in form. They vary in diameter from four or five inches to about a foot and a half. These stones have attracted the attention of many persons in Wick interested in natural science, and were brought to my notice by Bailie D. R. Simpson, of Wick, who has a large collection of them in his garden (Plate XII.).Bailie Simpson has suggested that their occurrence in the boulder-clay in the bottom of the harbour is due to transporta tion eastwards by the pr'eglacial Wick River. He attributes their peculiar shape to grinding in potholes in the preglacial river bed. He also notes that the sandstone of which they are composed is not seen in situ near Wick, so that they must have been brought from a distance.After a close inspection of the stones in Bailie Simpson's garden, I have come to a different conclusion for the following reasons. First-all the stones without exception are composed of the same rock, a yellowish or greyish micaceous sandstone. If they had been a collection of pothole stones carried by a river from a distance, we would have expected some variation in their composition. Secondly-though some are egg-shaped and smooth, others are not so, but show peculiar projections in dicating that their form cannot have been acquired by grinding in potholes. One specimen in particular shows a number of concentric sunken lines, and one at least is mammillated in the fashion often seen in calcareous sandstones.These facts in my opinion indicate that their outward form is due rather to concretionary action than to grinding in potholes.These stones are composed of a light greyish or yellow sand stone, unlike any of the Old Red Sandstone rocks seen in situ in the neighbourhood, or in the very perfect coast sections north and south of Wick; but it does resemble a sandstone containing Jurassic fossils found in the boulder-clay all over the east coast of Caithness. Attention to the glacial phenomena of the district shows clearly that these Jurassic rocks have been July 16, 2015 at West Virginia University on http://trned.lyellcollection.org/ Downloaded from

The last glaciation in Caithness, Scotland: revised till stratigraphy and ice-flow paths indicate multiple ice flow phases

“…These erratics include large rafts at Leavad (Tait, 1912) and Wick (Tait, 1907). The source area for these erratics comprises much of the floor and western fringe of the inner Moray Firth (Figure 2).…”