The Volcanic Rocks of the Forfarshire Coast and the Associated Sediments

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Abstract
T he earliest description of the volcanic rocks of Lower Old Red Sandstone age, which are so admirably exposed on the coast of Forfarshire, we owe to the Rev. John Fleming, whose observations were in a remarkable degree unprejudiced by the theories prevalent at the time when he wrote. A fuller account of the rocks as they appear in the field is given by Sir Archibald Geikie in his ‘Ancient Volcanoes of Great Britain;’ but no attempt has been made, up to the present, to describe the rocks of this locality as they appear under the microscope, although similar rocks in adjoining areas have been so dealt with. The Geological Survey 1-inch maps clearly indicate the occurrence of a great anticline, a continuation of the Ochil Axis, which runs in a general east-north-easterly direction, passing out to sea near Montrose, where exposures of the oldest lavas may be seen. On following the coast southwards from Montrose, one meets with higher beds in the volcanic series; these extend as far as the Lunan-Bay sands, beyond which a newer and higher series of lavas forms the promontory that juts out eastwards on the south side of the Bay. These lavas are succeeded by sandstones, all dipping consistently south-eastwards. Broadly speaking, therefore, the field-relations of these rocks are quite simple. When, however, we descend to detail, the petrological similarity of the different lava-flows, their lenticular character, as, also the lenticular character of the conglomerates and sandstones which are found among them, make it very

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