XXXIV.—The Geology of South-Eastern Kincardineshire

In 1804, Lieutenant-Colonel Imrie communicated to the Royal Society of Edinburgh a paper entitled “A Description of the Strata which occur in ascending order from the Plains of Kincardineshire to the Summit of Mount Battoc, one of the most elevated points in the Eastern District of the Grampian Mountains.” He pointed out that, in a short stretch of six miles in the North Esk section, “we pass from the secondary horizontal strata of the newest formation to the vertical, contorted primary strata of the oldest date, and terminate with granite, the primitive rock in the conception of many geologists.”

An Early Devonian lake and its associated biota in the Midland Valley of Scotland

ABSTRACT

The Tillywhandland fish bed of the Lower Old Red Sandstone in the Strathmore area of the Scottish Midland Valley accumulated in a lake, here called Lake Forfar, which was created suddenly following a period of fluvial deposition. Lake creation may have been due to basin faulting or the disruption of drainage patterns by contemporaneous volcanic activity. The fish bed laminites accumulated in a hydrologically open lake under a seasonal climatic regime. When fully developed, laminites comprise repeated quadruplets of clastic silt/carbonate/organic/green clay–shale laminae averaging 0·5 mm in thickness. Following 2000 years of laminite deposition an increasingly silty succession with thin current-rippled sandstones provided the lake-fill.

The fish fauna is dominated by Mesacanthus and Ischnacanthus with rare Euthacanthus, Parexus, Climatius, Vernicomacanthus and Cephalaspis. Most fish carcasses were partially decayed before deposition in the laminites on the poorly oxygenated lake floor. Abundant coprolites are the result of predation on Mesacanthus and small Ischnacanthus, probably by larger Ischnacanthus. Arthropods present include eurypterids (Pterygotus), washed in as near complete exuviae and fragments, and millipeds which were washed in from surrounding terrestrial environments along with plants, of which Parka and Zosterophyllum are common. Bioturbation indicates that conditions were not permanently anoxic during deposition of the laminites.

Comparison of our collections with the Mitchell Collection accumulated in the 19th century indicates that Tillywhandland Quarry was the main source of specimens in laminite lithologies labelled ‘Turin Hill’.