Geological and Mineralogical Map of Sutherland

Abstract

ANYTHING relating to the Geology of Sutherland has a great interest for British geologists. It was there that the battle of the “North-West Succession” was fought out by Murchison, whose conclusions have been acquiesced in by most geologists. Notwithstanding the evident simplicity of the structure of the country, there have always been some who have demurred from his interpretation, and who, discovering a few inaccuracies in his work, have endeavoured to invalidate its general results. The last phase of this dissent has just appeared in the form of a geological and mineralogical map by Prof. Heddle, and accompanying papers on the Geognosy of Sutherland, published in the Mineralogical Magazine. The map clearly shows a lower gneiss separated by the wreck of a wide-spread unconformable formation of sandstones and conglomerates from a higher group of quartzites, limestones, and schists. Thus far it corroborates Sir Roderick. The author however tries to prove from the evidence afforded by chemical analysis that the Durness limestone with its lower Silurian fossils has no relation to any other rocks in the country, and consequently that there is no evidence of any other part of the Highland rocks belonging to the Silurian system. For this information we require to have recourse to the “papers,” as the map only indicates that the Erribol and Assynt limestones, which Murchison and most geologists have identified with those of Durness, are dolomitic. They are therefore expressed by different colours. The physical and palæontological evidence, however, appears to be entirely against this notion.

Geological and Mineralogical Map of Sutherland.

By M. Foster Heddle, &c., President of the Mineralogical Society of Great Britain and Ireland.