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examined this ditch in 1850. The deposit is from one to three feet below the surface, and traceable one or two hundred yards. An excavation about seven feet in depth was made, and the section presented irregular layers of unctuous clay, of a dark brown colour and soapy feel, and so tough and adhesive as to render it a work of considerable labour to dig it out. Interstratified with this clay were thin layers of a compact sandstone. These layers of sandstone were not continuous ; they graduated into each other, thinned out, disappeared, and reappeared, most confusedly. They were very much inclined, dipping towards the south. The whole mass had much the appearance of having been drifted; although, from the nature of the matrix, and the state of preservation in which the shells are found, it does not appear as if it could have been transported far. The sandstone is tough and soft when newly dug, but hardens on exposure to the air, and becomes light-coloured in drying. When wet it presents a mottled appearance, the colouring being greenish; when dry, this almost disappears. The exterior surfaces are quite reddened with iron. Many of the remains are casts, and are on the outer surfaces of the fragments of sandstone as well as in the interior of the masses. Of the remains themselves, flattened spatangi are most abundant. Mr. Salter and Mr. Baily have named twenty species from my specimens, and Mr. Salter considers these clearly conclusive that this fragment belongs to the “Upper Greensand.” Some of the species are new.
Flints, as you are aware, are found in the highest beds of the cretaceous group, and they seem to be invariably formed around some organic body. I do not enter to-night into the various theories (principally those of Dr. Buckland and Mr. Bowerbank) as to their origin, but will only quote Mr. Ansted's remark regarding them: “They are,” he says, “equally puzzling to the geologist, the chemist, and the zoologist." I may add, when they are found, as in Buchan, overlying the granite, they form a geological problem about as hard to solve as their own substance.
From our brief survey of the surrounding country, we saw that the predominating rocks are the crystalline and the stratified unfossiliferous. Only in one instance did we find a limestone with organics (an ammonite), which might consequently belong to a later formation. Old red sandstone occurs at Aberdeen, again certainly at Gamrie, but it has not been positively seen at any point between, although it has been supposed that it may nevertheless envelope the primary rocks along the coast beneath the sea level. Oolite and wealden beds occur in the neighbourhood of Elgin. The distance between these beds at Llanbride and the flints of Buchan cannot be less than fifty or sixty miles. Water-worn fossils of the Lias occur at Blackpots, near Banff, but there they are manifestly in a drifted clay. The old red sandstone is the newest rock that is known to occur over all Banffshire, consequently the whole of that county comes between the deposit under consideration and the newer formations of Morayshire.
This newly-determined greensand of Cruden is the only rock at all approaching, in the geological sequence, the chalk beds from which the chalk flints must have been derived. We have been forced to conclude concerning it, that if it is not in situ, it is at least not far removed from it.
The question then arises, How came the flints there, and whence?
Mr. Hugh Miller, cautioning the young geologist against concluding that because he finds a rock resting upon gneiss it is therefore low in the geologic scale, instances, as an example of the error such a conclusion would lead to, the flints and chalk fossils of Banff and Aberdeen lying immediately over it in these counties; and adds, “It is probable that the
denuded members of the cretaceous group once rested upon it there."
Dr. Jameson, too, in the Edinburgh Philosophical Journal for 1831, states the same opinion, adding that it will probably be found in some of the hollows of this part of Scotland.
This is one theory: That the lower beds, and the chalk of this very bed itself, have been removed by denudation, leaving the flints resting upon the granite.
Opposed to this theory is the fact that the flints are invariably water-worn. True, even according to it they would have presented some such appearance, but hardly to the same extent; and it seems as if a denuding agency, sufficiently powerful to produce the rolled effect noted, would have removed them, as well as the other beds and their chalk matrix, especially as they occur not so much in hollows as on the sides and summits of hills.
Mr. Nicol states his opinion thus: “Probably these recent secondary formations once existed here, or may still be covered by the sea, and connected with the similar beds on the Moray Firth. This opinion is confirmed by the occurrence of lias containing coal at Hogenaes, in the south of Sweden, where it rests on gneiss, and is covered with chalk."
This leads on to another theory which has been suggested to account for these flints-namely, that however such secondary beds may have once existed here, these individual waterworn flints owe their origin to a transporting agency, which has brought them from the chalk formations of the Northern Continent.
The volcanic and tidal agencies operate in a direction between south-west and north-east. All the mountain ranges and great formations of our island assume in the general that direction. The great mountain range of Norway assumes the same. I am not sufficiently acquainted with Norwegian geology to connect it skilfully with Scottish. At
Christiania there is a group belonging partly to the lower and partly to the upper Silurian rocks. True chalk with flints has been clearly determined in some parts of Denmark. This Danish group may have been continued into Norway at one period, and afterwards removed by denudation, the same agency transporting the flint nodules to our own shores.
It may bear against such a supposition of transportation, that the direction of the currents seems usually to have been from south-west to north-east, and that for this theory it requires to have been reversed. It may be suggested, 'Might not the elevation of the great northern mountain ranges of the Continent have been sufficient to cause a tidal wave or current from its shores to these of ours, capable of exercising the transporting power required? The presumption is, however, against such a supposition.
Standing on the ridge of the hill of Kinmundy, and looking towards the south and east, there is spread out before the eye a wide expanse. Slightly to the north of eastward the ridge is continuous to the sea at Buchan-ness. Westward it undulates, receding northwards, and again stretching out a promontory to the south. Beyond this there is
gorge narrow and deep, and again the hill rises, stretching away westward and northward, and running out in a series of high grounds by Dudwick towards Turriff and Delgaty, and so onwards to the sea at Boyndie. Between this ridge and the sea, on the east and south-east, there stretches out, from the sort of bay described, a breadth of five or six miles of levelish country, presenting inequalities of surface and some rising grounds, but in the main levelish till it reaches the sea, with a coast line elevated one hundred and eighty to two hundred feet above the sea level. It is over this valley that the calcareous sands (crag) occur. It is near its centre that the greensand lies; and standing, as I have said, on the hill ridge, and marking, as one cannot fail to mark, the band of flint boulders that line near their highest, and at an equal elevation, the various bays and promontories, it requires no great stretch of imagination to conceive of the waves of the German Ocean as having once rolled even hither, bearing with them, and depositing on their innermost bounds, the rounded flints that mark their ancient shore.
But it may be argued, The greensand beds lay right in the way,
and must have suffered also from the denuding power of the waves.
If future examination shows that these beds are in situ, we must yet look for another theory.
I have already stated that the shores of the little bays near Peterhead present large quantities of the rounded flints. These may have been either brought down by streams, or cast up from the sea. I have also inferred, from the condition of my specimens of organic remains from the Cruden greensand, that that formation is either in situ, or at least not far removed from its original position, —not presenting any evidence of being water-rolled, and not capable of undergoing without destruction that process.
I wish to connect these two facts with an idea hinted at by Nicol, as already quoted, and additional grounds for which have been pointed out to me by Mr. Hugh Miller. Across the southern districts of England, we have a certain sequence of geological formations, including in regular succession, the lias, oolite, and wealden, succeeded by the cretaceous group. Across that portion of Scotland immediately to the north of the district at present under consideration, we have part of the same sequence, commencing with the lias. This formation at Cromarty is considerably to the west of the first appearance of the same formation in England: but this results naturally from what was before mentioned of the geological formations, running not east and west, but north-east and south-west, not right, but diagonally, across the country. We have then lias, at Cromarty; and a lower oolite, near Elgin