Man and the Glacial Period

by G. Frederick Wright

In North Wales the Vale of Clwyd contains numerous caves which were occupied by hyenas in preglacial times and with their bones are associated those of the mammoth, the rhinoceros, the hippopotamus, the cave-lion, the cave-bear, and various other animals. Flint implements also were found in the cave at Cae Gwyn, near the village of Tremeirchon, on the eastern side of the valley, opposite Cefn, and about four miles distant. We have already given an illustration of the Cefn cave (see [page 148]). It will be observed that this valley of the Clwyd opens to the north, and has a pretty rapid descent to the sea from the Welsh mountains, and was in position to be obstructed by the Irish Sea glacier, so as to have been occupied at times by one of the characteristic marginal lakes of the Glacial period. It is evident also that the northern ice prevailed over the Welsh ice for a considerable portion of the lower part of the valley; for northern drift is the superficial deposit upon the hills on the sides of the valley up to a height of over 500 feet. From the investigations of Mr. C. E. De Rance, F. G. S.,[DC] it is equally clear also that the northern drift, which until lately sealed up the entrance of the cave, was subsequent to its occupation by man, and this was the opinion formed by Sir Archibald Geikie, Director General of the Geological Survey of the United Kingdom, as the result of special investigations which he made of the matter.[DD]

[DC] Proceedings of the Yorkshire Geological Society for 1888, pp. 1-20.

[DD] See De Ranee, as above, p. 17; and article by H. Hicks, in Quarterly Journal of Geological Society, vol. xlii, p. 3; Geological Magazine, May, 1885, p. 510.

From the caves in the Vale of Clwyd as many as 400 teeth of rhinoceros, 500 of horse, 180 of hyena, and 15 of mammoth have been taken. A section of the cave deposits in the cave at Cae Gwyn is as follows:

“Below the soil for about eight feet a tolerably stiff boulder-clay, containing many ice-scratched boulders and narrow bands and pockets of sand. Below this about seven feet of gravel and sand, with here and there bands of red clay, having also many ice-scratched boulders. The next deposit was a laminated brown clay, and under this was found the bone-earth, a brown, sandy clay with small pebbles and with angular fragments of limestone, stalagmites, and stalactites. During the excavations it became clear that the bones had been greatly disturbed by water action; that the stalagmite floor, in parts more than a foot in thickness, and massive stalactites, had also been broken and thrown about in all positions; and that these had been covered afterwards by clays and sand containing foreign pebbles. This seemed to prove that the caverns, now 400 feet above ordnance datum, must have been submerged subsequently to their occupation by the animals and by man. In Dr. Hicks’s opinion, the contents of the cavern must have been disturbed by marine action during the great submergence in mid-glacial times, and afterwards covered by marine sands and by an upper boulder-clay, identical in character with that found at many points in the Vale of Clwyd. The paleontological evidence suggests that the deposits in question are not preglacial, but may be equivalent to the Pleistocene deposits of our river-valleys.”[DE]

[DE] H. B. Woodward’s Geology of England and Wales, pp. 543, 544

If the views of Professor Lewis and Mr. Kendall are correct concerning the unity of the Glacial period in England, the shelly and sandy deposits connected with these Clwydian caves at an elevation of 400 feet or more would be explained in connection with the marginal lakes which must have occupied the valley during both the advance and the retreat of the ice-front; the shells having been carried up from the sea-bottom by the ice-movement, after the manner supposed in the case of those at Macclesfield and Moel Tryfaen. If, therefore, the statements concerning the discovery of flint implements in this Cae Gwyn cave can be relied upon, this is the most direct evidence yet obtained in Europe of man’s occupation of the island during the continuance of the Glacial period.

In all these caves it is to be noted that there is a sharp line of demarcation between the strata containing palæolithic implements and those containing only the remains of modern animals. Palæolithic implements are confined to the lower strata, which in some of the caves are separated from the upper by a continuous bed of stalagmite, to which reference will be made when discussing the chronology of the Glacial period. The remains of extinct animals also are confined to the lower beds.

The caves which we have been considering in England are all in limestone strata, and have been formed by streams of water which have enlarged some natural fissures both by mechanical action in wearing away the rocks, and by chemical action in dissolving them. Through the lowering of the main line of drainage, caverns with a dry floor are at length left, offering shelter and protection both to man and beast. Oftentimes, but not always, some idea of the age of these caverns may be obtained by observing the depth to which the main channel of drainage to which they were tributary has been lowered since their formation. But to this subject also we will return when we come specifically to discuss the chronological question.

The Continent.