Observations nouvelles sur le Tufeau de Ciply et sur le Crétacé supérieur du Hainaut

Abstract

IN view of the stratigraphical gap that exists in this country between the Chalk with Belemnitella mucronata and the Thanet Sands, the papers thus re-issued in a collected form have an interest considerably beyond the district with which they immediately deal. The value of passage-beds being that they blur over the hard-and-fast lines laid down by our earlier conceptions, it may seem ungrateful to define the exact upward limit of deposits such as those which close in the Danian series. The observations of the authors, however, go to show that the Tufeau de Ciply of the Mons basin, which has been hitherto referred to the Maestrichtian—a fact incorporated in ordinary textbook information—is in reality intimately connected with the Montian. A close examination of 3000 kilogrammes of the conglomerate that forms its base has yielded rolled Thecideæ and Cretaceous Bryozoa; but the principal fauna, as indicated by casts of unrolled shells, is of distinctly Tertiary type, containing such representative forms as Cerithium montense, Voluta elevata, and Turritella montensis. The beds near St. Symphorien, correlated with those of Ciply by MM. Cornet and Briart, are divided by the authors into the true Tufeau de Ciply, with its conglomeratic base, and the “Tufeau de St. Symphorien,” with Belemnitella mucronata, Thecidea (Thecidium) papillata, &c., which is seen to rest, also with the intervention of a conglomerate, on the Senonian. The lower of these horizons is incontestably Maestrichtian; it remained to show that the Tufeau de Ciply, on the other hand, passes up continuously through the Cerithium limestone of Cuesmes into the Calcaire de Mons. To outsiders, unfortunately, the evidence is not complete. The junctions in the field are still obscure, and even the lack of parallelism between the Tufeaux of Ciply and St. Symphorien is mainly based on palæontological arguments, both beds alike resting in places on the uppermost Senonian, The sharp distinction of the two faunas leaves, however, little room for doubt; and the alliance of the Ciply beds with the Montian is still further emphasised by the occurrence in them of large Cerithia, of which the authors record two new species, appropriately named corneti and briarti. It is probable, then, that when, by fortunate excavations in this phosphatic area, the necessary junctions become exposed, MM. Rutot and Van den Broeck may be congratulated on having added beyond recall some 20 or 30 feet to the Tertiary beds of Europe.