XXIX.—On the Geology of the Thracian Bosphorus.

Abstract

During a short residence at Constantinople, in March 1836, I made some researches into the geology of its vicinity. A very cursory examination sufficed to show, that the district was unexplored, and that the brief geological remarks, which exist in the works of other travellers, are very unsatisfactory. I therefore communicate my observations to the Society, in the hope that, though slight, they may serve as a guide to those geologists who may hereafter be induced to explore this interesting district*. The formations in the neighbourhood of the Bosphorus may be classed as follows:— 1. Silurian schist and limestone. 2. Igneous rocks. 3. Tertiary limestone. 4. Ancient alluvium. 1. Silurian Schist and Limestone. This formation occupies both sides of the Bosphorus for about three quarters of its length, and extends thence towards the W.N.W. and E.S.E., to an unascertained distance in Europe and Asia. It may probably form a great part of the Balcan range, of which the hills above the Bosphorus are a continuation. The formation may be described as a mass of argillaceous schist, compact brown sandstone, and compact dark blue limestone, passing into each other by insensible gradations. The argillaceous schist predominates greatly over the other two rocks, and frequently exhibits an oblique or slaty cleavage. The whole formation bears a close analogy to the lower Silurian and upper Cambrian series, exhibited in Wales and Devonshire. From its resemblance to the type of northern Europe, Andreossy* and an American traveller† referred it to the transition series on