UPTHRUST MARINE MUDS 267 



low elongated mound with occasional conical projections. One of these is shown in 

 Plate LXXXVII. The raised beach proper is capped by angular blocks of moraine 

 material, chiefly formed of quartz and felspar porphyry, with thin greenish crusts of 

 epidote. Associated with these blocks were fragments of apatlte-allanite-granite, 

 these fragments being mostly smaller than those of the quartz- and felspar- 

 porphyries. Some of these pieces were striated, others showed evidence of having 

 been crushed, apparently by ice pressure. Occasional blocks were observed of a 

 very curious porphyritic granite with singly twinned orthoclase crystals up to 

 4 inches in length. Fig. 62 illustrates the mode of occurrence of this raised beach, 

 or more probably upthrust marine mud. 



From this it will be seen that the top of the cone is formed of breccia, composed 

 of blocks of granite, quartz-porphyry, &c. This rests on the french-grey marine 

 muds, and these in turn repose on a conical mass of ice. The base of the cone is 

 surrounded, as shown in the sketch, by the larger blocks of the moraine. It was 

 a great surprise to us to find a foundation of ice underneath the raised beach. We 

 tested this ice and found it was slightly saline superficially, but not as salt as 

 typical sea ice. We observed that some of the serpula^ tubes were attached to the 

 blocks of quartz- and felspar-porphyry as well as to the granite. It may be argued 

 that such tubes probably became attached to these blocks below present sea-level, 

 and that the blocks had subsequently been pushed u^j by ice pressure up to their 

 present elevation of about 20 feet above sea-level. This explanation is slightly more 

 difficult of application to the large delicate siliceous sponge attached to the granite 

 block, and shown in the sketch. (B enlarged. Fig. 62.) 



This sponge was about 2 feet long and 1 foot wide, built up of delicate siliceous 

 fibres woven into at least sixteen distinct sacks, as shown In the sketch. The whole 

 structure was delicate and fragile, and yet perfectly preserved. It was obvious 

 to us that this sponge was in position of growth, and that the block to which it 

 was attached must have been under the sea at the time. This block was only a few 

 feet above sea-level, but was evidently part of the raised marine muds, which, as 

 already stated, ascend to a little over 20 feet above sea-level. Thei'e is here a somewhat 

 difficult jDroblem. How ai-e we to account for the existence of a raised marine 

 deposit over a surface of ice ? The Ice on the whole appears to be laud ice, with 

 its surface rendered saline by submergence in sea water. How can ice, which is 

 so much lighter than water, be held under the water so as to admit of marine 

 deposits being formed on top of It ? Much light has recently been thrown on the 

 subject of so-called Ealsed Beaches In Arctic areas by an important paper by G. W. 

 Lamplugh, F.R.S.,* as well as by Professor A. G. Nathorst.f 



Professor De Geer has also given a very interesting account of the glacial 



* " On the Shelly Moraine of the Sefstrtim Glacier and other Spitzbergen Phenomena illustrative 

 of British Glacial Conditions." Proc. Yorkshire Geol. Soc, vol. xvii,, part 3, 1911. 

 t Bull. Geol. Instit. of XJpsala, 1910, vol. ix. pp. 261-415. 



