On the Carboniferous and Silurian Formations of the neighbourhood of Bussaco in Portugal

Abstract

The Palaeozoic deposits of Bussaco are bounded on the west by newer deposits, which have been partly described by Mr. Sharpe: before entering upon the principal subject of this memoir some remarks are added which serve to connect his observations with those which follow here. Jurassic Series.—In the Val de Gorgorao, half a mile north of Coimbra, is a limestone with many species of shells, the same as those of Mealhada, which probably belongs to the Inferior Oolite†. This rests on the limestone of Montarroio in Coimbra, in which were found the carapace of a Turtle and many shells absolutely different from those of the Jurassic rocks of this district; but it contains neither Ammonites nor Belemnites. The shells have some analogy to those found at Chao de Lamas and Cinco Villas, ten and eighteen miles south of Coimbra, which will be mentioned presently, one of which resembles Posidonia minuta , while others are probably Mytili . Immediately below the above and resting conformably on the Red Sandstone, with which it contrasts strongly in colour and mineral characters, is a group of beds not exceeding five metres in thickness and of limited extent, observed at Lordomao, one mile north-east of Coimbra, in the Quinta di Varzea, and at Pereiros on the side of the road to Thomar, three miles south of Coimbra: the lowest beds are of a coarse grey sandstone, covered by a series of thin beds of fine calcareous sandstone of a dark yellow colour, alternating with yellow marl and