On the Series of Upper Palæozoic Groups in the Boulonnais

Abstract

In May 1852 I accompanied Prof. Edward Forbes, Mr. Prestwich, and Mr. Morris in a geological excursion into the Boulonnais and part of Belgium: the examination which we were enabled to make of the district about Marquise, though brief, was sufficient to satisfy us that the Palæozoic group there had not been described with sufficient precision and detail. I therefore visited it again in the autumn of the same year, and on that occasion I was joined for several days by Mr. Daniel Sharpe. The Lower Boulonnais is a district of the province of Artois, which has for its natural limits the escarpments of the chalk formation: its breadth from north to south, as from Wissant to Verlinctun, is about fourteen miles; and its length, from Boulogne to Lottinghen, about twelve. This district has been of interest to the English geologist, since its physical features were first noticed by MM. Conybeare and Phillips, as it constitutes the eastern extension of our Wealden denudation. In the extreme north-east angle of this area, a little beyond the village of Marquise, and at the very base of the chalk escarpment, there is a very limited tract, which is the subject of the present communication.See Map, Plate X. The palæozoic rocks of the Boulonnais were described by M. Rozet in his general memoir on that district, and they occupied much of the attention of the French and English geologists during the Réunion Extraordinaire at that place in 1839. M. Rozet attempted to place the