ELEPHANT AND CLARENCE GROUP 79 



the foot of a precipitous mountain wall rising behind the beach where he landed, and from wave- 

 rounded boulders. He gives the following brief particulars: 



The rocks are rather highly metamorphic, grey or greenish in colour, with a more or less distinct schistosity, 

 rather fine-grained, most of them, however, showing a crystalline texture well already {sic) to the naked eye. 



A grey rock is, according to Broch, a fine-grained albite-epidote-biotite-schist, with quartz and hornblende, 

 further muscovite, titanite, apatite. A chemical analysis shows an andesitic composition.' 



A greenish chlorite-schist has a basaltic composition. A grey rock, with hardly any schistosity and less fine-grained, 

 is by Broch found to be mainly made up of albite, epidote, hornblende, biotite. It probably represents a highly 

 altered basic igneous rock. 



These greenish or greyish rocks show a fairly distinct bedding that may be seen in pi. xxiii, fig. 3. The dip is there 

 rather var^'ing both as to inclination and direction. The main direction of the strike is probably south-west to north- 

 east, parallel to the north-western coast. Such a strike is at any rate typical of the extreme western part of the island. 



The strike of the rocks in Clarence Island is thus not very different from that in Elephant and 

 Cornwallis Islands, and it is to be expected that the same or similar rock types will recur in Clarence 

 Island. From the above brief description of the rocks it would appear that they are comparable in 

 mineral composition and metamorphic grade with those described by Tilley from the southern point 

 of Elephant Island. 



In the preface to his memoir Holtedahl says that his rock specimens had been assigned to O. A. Broch 

 for petrological investigation. Eventually, however, the work was taken over by T. F. W. Barth and 

 P. Holmsen.- 



In regard to Clarence Island, Barth and Holmsen give very brief descriptions of a 'common 

 schistose greenstone' and a chlorite-schist, of which analyses are given. In their Table of Analyses 

 (p. 60, op. cit.) these rocks are designated respectively as: biotite-epidote-actinolitc-albite-schist, and 

 chlorite-actinolite-clinozoisite-albite-schist. These analyses are discussed later (see Table 6, p. 87). 



DREDGED STONES FROM SOUTH OF CLARENCE ISLAND 

 Among the Discovery II material submitted to me was a box containing numerous stones dredged 

 on 23 February 1927 at St. 170 at a depth of 342 m. The exact position is long. 61° 25' 30" S., lat. 

 53° 46' W. On Chart no. 6^ a sounding of 342 m. is shown about 7 miles south-west of Cape Bowles, 

 the southernmost point of Clarence Island, but this sounding is shown on the chart at lat. 54° 15' W., 

 the longitude being the same as that given above. The position of this sounding is about 30 miles 

 east-south-east of the eastern coast of Elephant Island. 



The question of the provenance of the stones is rather difficult. It depends on the prevalent direction 

 of the marine currents near Clarence Island, both as affecting direct transport of the stones, and 

 as influencing the drift of icebergs which may have carried the stones or some of them from Elephant 

 Island, or even from more southern localities. It will be assumed that the majority of the stones came 

 from Clarence Island, some from Elephant Island, and possibly a very few from the south. 



PETROGRAPHY 

 The stones range in size from about 3 in. in greatest diameter down to half an inch. They are all 

 covered with a thick growth of calcareous marine organisms. When this is chipped or dissolved off 

 it can be seen that most of the stones consist of fine-grained grey and green schistose rocks, often 

 profusely veined with quartz. Thirty-five of the stones were sectioned for petrographic examination. 

 Four were found to be igneous rocks, three sedimentary, and twenty-eight metamorphic. 



1 This is presumably the analysis of a 'schistose rock' quoted on p. 109 of Holtedahl's memoir. 



2 'Rocks from the Antarctandes and the Southern Antilles', Scient. Res. of the Norwegian Antarctic E.xpeditions, 1927-28 

 and 1928-29, No. 18, Norske Vidensk.-Akad., Oslo, 1939, 64 pp. (Clarence Island, pp. 59-60). 



3 H. F. P. Herdman, 'Report on Soundings taken during the Discovery Investigations, 1926-32', Discovery Reports, 



VI, 1932. 



6-2 



