Transactions of the Geological Society, 1st series, vol. 4/Geological Remarks on the Vicinity of Maestricht
By the Rev. W. E. HONY, Fellow of Exeter Coll. Oxford.
member of the geological society.
[Read 16th December, 1814.]
The interest excited by the magnificent specimens which have been discovered at different times in the neighbourhood of Maestricht, induced me when in the Low Countries in the summer of the present year, to go somewhat out of my way in order to visit so celebrated a spot. I am sorry that my stay there was necessarily so short that I could take only a very hasty survey of that country. I am induced however to lay before the Society a short sketch of what I saw, because I believe that though so much has been written and said on the subject of the fossils of Maestricht, but little is known in England as to the relative situation of the strata containing them. The mountain of St. Pierre commences about a mile south from the town of Maestricht, and extends in a direction towards Liege for nearly three leagues. It is an insulated hill forming a ridge, the sides of which are for the most part very steep. The subterraneous quarries must have been worked from a very early period, and are said to extend through its whole length. The hill presents an almost perpendicular escarpment towards the Meuse, and it is in walking on this side of it that the strata are seen to the greatest advantage.
About a league from Maestricht you obtain a good section of the lower beds of the hill, and these are decidedly chalk, containing beds of flint nodules from two to three feet distant from each other. The chalk appears to contain fewer fossils than that which we have in this country, but in the nature of these fossils, and in every other respect, completely resembles it.
Above these are beds resembling the chalk in colour, but more hard and gritty to the touch.
Above these again lie a succession of beds of the calcareous freestone of which the mass of the hill is composed, and it is in these that the quarries are situated. This stone is of a yellowish colour, and so extremely soft in the quarry that it may be easily cut with a knife; it becomes however of a lighter colour and more hard by exposure to the air. Here and there is found a thin stratum completely made up of fragments of marine substances; these are chiefly species of corallines and madrepores mixed with shells. In these thin strata the remains are much less perfect than in those which contain fewer of them, and their substance is so extremely tender that it is very difficult to obtain a specimen which does not break to pieces immediately. Such parts of the rock, though of course unfit for building, are not useless, but are broken down, and in that state conveyed by the Meuse to Holland as a manure for the meadow land.
The whole of these beds from the chalk to the top of the hill are separated from each other by beds of flints, which exactly resemble those found in the chalk, presenting like them the usual appearance of having been formed on corallines, &c.
The beds of flints in the chalk and lower strata of freestone, as has been mentioned, are at a distance from each other of not more than two or three feet, but as you ascend, the distance between them is greater, and towards the upper part of the hill is as much as eight or ten feet.
These flints frequently contain organic remains; of these the most common is the belemnite; shells also and silicified wood are not uncommon.
The height of the hill above the Meuse is I should imagine about 150 feet.
To the eye the strata appear to be perfectly horizontal. As however, I found the chalk gradually rising as I proceeded in a direction nearly south, it is probable that there may be a very slight inclination towards the north. My stay was too short to enable me to give any account of the numerous fossils of this rock. I may however mention that those which I found most common were various species of corallines and madrepores, (particularly the fungites;) belemnites; numulites; several species of echini, amongst others, a small one having the mouth in the centre of the base and vent lateral; several kinds of oysters and pectines. I was also fortunate enough to find a very beautiful baculites with turrited articulations, but this I believe is very rare. It is described in the 3d vol. of Parkinson's Organic Remains, p. 142.
The top of the hill is covered by a bed of gravel, in some places of considerable thickness, containing rolled pebbles of flint, white quartz, graywacké containing veins of quartz, and a red sandstone. I believe that this gravel rests immediately on the strata which compose the hill, and that the beds of sand which M. Faujas de St. Fond thought he perceived under the gravel are only a part of the rock in a state of decomposition.
It is rather extraordinary that this celebrated naturalist should have described the freestone rock of Maestricht as “ un grès quartzeux faiblement lié par un gluten calcaire.” It appears that it is almost wholly calcareous, containing little or no siliceous matter.
Geologists will of course be anxious to learn whether these beds, occupying a situation similar to that of the Paris strata, are identical with any of them. I am myself too little acquainted with the latter to form any opinion on the subject. I am inclined to think however that the Maestricht rock differs from all the beds which form the Paris basin.
It would be departing too much from common language to call it chalk; but the gradual transition of the chalk into the freestone, and the separation of the strata from each other by parallel beds of flint, seem to be sufficient reasons for including it in the chalk formation.
When nearly at the southern extremity of St. Pierre I crossed over to the right bank of the Meuse to examine a rock which rises very boldly near a little town called Visé. This rock I found to resemble the limestone of Derbyshire, containing all the fossils characteristic of that formation, and like it frequently passing into chert. The fossils most abundant are several species of anomiæ and entrochi: the latter are more particularly abundant in the chert. In some pieces I also found that species of coal which is called anthracite included in veins of calcareous spar.
In the country round Liege, distant about two leagues S.W. of this place, there are (as is well known) extensive collieries.