On the Marine Fauna of the Boulder Clay

On the Marine Fauna of the Boulder ClayAuthor(s): Joseph WrightSource: The Irish Naturalist, Vol. 11, No. 11 (Nov., 1902), pp. 270-272Published by: Irish Naturalists' Journal Ltd.Stable URL: http://www.jstor.org/stable/25522226 .

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270 The Irish Naturalist. November,

ON THE MARINE FAUNA OF THE BOULDER CLAY.

BY JOSEPH WRIGIT, S.G.S.

He had examined microscopically I I2 samples of Boulder clay from

various places in the British Isles and in Canada; 47 of these were from

Ireland, 27 from England and Wales, 22 from Scotland, I from the Isle

of Man, and 14 from Canada. In 7I of the British and 9 of the Canadian

samples Foraminifera were found. The specimens of the clay had been taken from various altitudes, some few of them from localities over r,ooo

feet above the sea. Almost all the forms found were referable to species

which at present lived at moderate depths off our coast, and most of

them had the fresh appearance of these species. Notnionina depressula was

often met with in great profusion, fully one-half of the entire specimens found being referable to this species. One hundred and thirteen species had been found in the clays of Ireland, 72 of those in the Isle of Man, 66

in England and Wales, 40 in Scotland, and Is in Canada. In 31 of the

gatherings no Foraminifera were met with, whilst in some of the others they were very rare. The absence or the scarcity of specimens in some

of the samples might be due, in part at least, to the circumstances that

it was only the first floatings from the clays that were examined, and

also that these minute organisms were liable at times to be overlooked

when the material was being examined. To ascertain how far floatings

could be relied on for giving conclusive results, xoz. troy of the Boulder

clay from Woodburn, near Carrickfergus, was examined with the utmost

care. The first floating was found to contain I,400 specimens, the floating process being repeated twenty-five times before specimens ceased to come up; upwards of 6oo additional specimens were thus obtained. What re

mained of the clay was then examined in detail with the microscope,

and 67 more specimens were got from it. In the Bculder clay at Knock

Glen, near Belfast, 79 species were obtained, many of them being very rare forms, 6 being only known as recent British species froni collections on the west coast of Ireland, two of these also occurring off the west coast

of Scotland. The presence of these microzoa would lead them to infer that the clay at this place was probably deposited in deep water, when

the land stood at a much lower level than at present, and when the

marine conditions must have been somewhat similar to what now pre vails off the west coast of Ireland. At Woodburn, near Carrickfergus, the clay was very similar to that at the Knock Glen, being very fine andi comparatively free from stones. Here also three of the west of Ireland

foraminifera occurred, also an exceptionally large specimen of Cornu sjira involvens. It was many diameters larger than any specimen seen by the author from recent British gatherings. In size it closely resembled an allied form of Cornuspira carinata, taken in dredgings off the west of

Ireland. Some of these west of Ireland forms have also been found in

Boulder clay at other places. Lagena fimbriata was found at five other localities besides those of Knock and Woodburn, one of these being at

Larch Hill, County Dublin, 8oo feet above the sea, and Polyseomle/ja subnodosa was got in Ayrshire at I,071 feet elevation.



190. The British Association in Belfast. 271

Mr. G, W. LAMPLUCH said they were all under a deep debt of grati

tude to Mr. Wright for his address with reference to the organisms of the

Boulder clay. They knew how devoted he was in his work, and if they

did not quite agree with his conclusion it did, not diminish their appre

ciation of his labours in that field of inquiry. With this statement he would go on to criticise. MrWright's conclusions were that the Boulder clay beds were marine because of the presence of the little organisms they contained. In his view Boulder clay was not in the strict sense of the term sediment; it was rehash of beds already in existence. They had the Boulder clay in this neighbourhood made up largely of the characteristic rock over which the breaking-up agency passed, and they

must expect to find in it the same class of organisms. The general study of the drifts showed them that Boulder clay was derived from the action of an ice sheet. Some of the areas referred to by Mr. Wright as instances in support of his theory came within the area of the work of the Geological Survey last year, and in the Dublin beds wherever

they found shells they also found fragments of Ailsa Craig eurite. They were only beginning with the Belfast area, but already they had come across similar phenomena. On the top of Divis Mountain, the Belfast

Naturalists'Field Club had found a fragment of Ailsa Craig eurite, where Mr. Wright had discovered traces of Foraminifera. The other evidence of the glaciation of this region one could scarcely find time to refer to, but the main point he would make was that the arrangement of the drifts was incompatible with the marine theory. The body of evidence in favour of the glacial origin of these deposits was so weighty that they need not hesitate to accept it.

Prof. W. BoYD DAWKINS said Mr. Wright had drifted into a very complicated and extremely important question. He quite disagreed

with Mr. Lamplugh. It was for him much easier to believe that clay containing marine materials had been accumulated under marine condi tions than to imagine that it had been deposited on the land from melting ice. There were several difficulties in the way of the land ice theory.

The first that had to be met was the motive force. Where did the vast field of ice get its motive force from so that it could override elevations up to 1,300 feet? It seemed to him there was no evidence of any such

motive power that could bring ice all the distance from Scandinavia to Ireland. The next difficalty was if the glaciation was from the sea to the land then the land would be glaciated from the sea. But that was not what they found; they found that the conformation of the rocks showed glaciation from the higher to the lower levels. This difficulty so far had never been grappled with by any one belonging to the land

glaciation school. Then the organisms were as perfect as they could be, Would this be so if they were to suppose that such delicate things as

those were fished up from the bottom of seas and carried by the

stupendous impact of masses of ice to the elevation of 2,000 feet ?

He was not one who shared the views of the younger school of geolo

gists and chipped away the views of Lyell and others as of no account.

B 2



272 The fish Naturalist. November,

Prof. P. F. KENDA4L (Yorkshire College) said a challenge had been given on that subject year after year, and were it not that Professor Dawkins had gone out to attend another meeting, he would have seen it fought out to the end. Marine organisms were always found in the

Boulder clay associated with transmarine erratics. This was the one thing in favour of the glacial origin of the Boulder clay, but a weightier argument was the fact that in those beds they found fragments of various formations, which could not possibly have been there had they been a later marine deposit. Mr. H. W. MONCYT0oN wished to know if such delicate fossils as the

organisms found in Boulder clay could travel long distances without being damaged.

Mr. LOMAS said it was more reasonable to believe that the Boulder

clay was an ice deposit than to believe that it was formed by marine action.

A member of the audience replied to Mr. Monckton's question. He

said in the mammal beds near Cambridge he had got Chalk Forminifera which were in excellent condition, although they had been denuded

from the surrounding hills. Mr. WiiuAM GRAY said those were siliceous Foraminifera. The member who had giventhe reply did not think Mr. Gray was right. Mr. WRIGHT briefly replied, maintaining the view he had taken in his paper.

REPORT OF THE COMMITTEE1

APPOINTED TO EXPLORE IRISH CAVES.

This Report, illustrated by lantern slides, was brought before the Section by Mr. R. J. USSHnR.

IN I90I, the Committee directed their energies to exploring a series of caves situated on the slope of Keishcorran Mountain, fifteen miles south of Sligo. The caves occur along the foot of a range of low cliffs, with a steep talus below them. The first cave explored (Coffey cave) showed a surface layer with remains of Red Deer and of man similar to those

found in raths and crannogs, under which was a breccia with bones of

small mammals, among which the Arctic Lemming, hitherto unknown as an Irish species, was abundant. This bed overlay clay which also

yielded bones of Lemming. A second cave (Plunkett cave) was dug; the upper stratum yielded a stone celt, iron saw, two bronze pins,

mussel and oyster shells, and abundant remains of domestic animals; also a metatarsus of Reindeer, associated with charcoal, and many bones

of Brown Bear and Frog. Under this was a thick bed of clay, almost

devoid of remains of domestic animals, but full of Brown Bear remains, with Fox, Red Deer, Rabbit, Wolf, and Lemming, Frog and Field

I Dr. SCHARFF (Chairman), R. LbC PRAOEGRR, G. CorYrY, Prof. Cox,rc, Prot. CUNNINGHAM, G. W. LAMPIUGH, A. McHZNRY, and R. J. UssHza.



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On the Marine Fauna of the Boulder Clay