Vol. 69.] LOCH AWE STNCLIXE (ARGYLLSHIRE). 303 



The late Mr. Grant Wilson has pointed out [17, p. 24] that 

 ' dark crystalline limestone, accompanied by dark pbyllites, occur along the 

 eastern shores of Eilean Eigh and Eilean Macaskin in Loch Craignish.' 

 These island-exposures belong, according to their geographical 

 position, to the Shira Division, but I have had no opportunity 

 of visiting them. 



The Crinan Quartzites and Grits. 



This division consists for the most part of pebbly grits, many of 

 them sufficiently quartzose to deserve the name ' quartzite/ The 

 texture varies from bed to bed, and from place to place. Often the 

 rocks are very coarse, with large grains of blue or white quartz 

 and fresh felspar. Dr. Flett, in summarizing what is known of 

 the felspar-pebbles of the Loch Awe Group, says that microcline, 

 orthoclase (often perthitic), and oligociase are found in decreasing 

 order of abundance [18, p. 58]. The coarser grits are sometimes 

 definitely conglomeratic, carrying fragments of slate, limestone, 

 and grit. Such rocks are less frequently found in the basal 

 portion of the division, next to the Shira Limestone, than higher 

 up. Mention has already been made, however, of the conglom- 

 eratic base of the quartzite at Kilmory Bay. Grant Wilson states 

 [18, p. 65] that inland the conglomerate 



' maintains its characters for a distance of about 4 miles along the strike.' 

 Another instance of a similar nature was encountered by 

 Mr. Kynaston in a stream known as Allt Fearna. 3 miles south- 

 west of Dalmally. The base of the Crinan Quartzite, resting here 

 upon grey silvery phyllites with limestone-bands, in the Shira 

 position, is coarse and pebbly, and contains numerous fragments 

 identical in type with the underlying limestone [16, p. 28]. 



While the dominant rock in the Crinan Division is pebbly 

 quartzite or grit, there are numerous intercalations of slate and 

 limestone of varying character. As an example, one may cite 

 excellent exposures of grey slate and repeatedly interbedded fine- 

 grained quartzite and grey sandy limestone at Ardnoe Point, and 

 for 3 miles southwards along the shores of the Sound of Jura. 

 Similar beds occur along the eastern coast of Loch Craignish, and 

 have been recognized inland at many places ; but they are not 

 sufficiently differentiated to be mapped out separately as a sub- 

 division of the Crinan Quartzite. 



The Tayvallich Slates and Limestones. 



This division is connected with the Crinan Grits and Quartzites 

 by a transition-zone, in which there is marked interbedding of black 

 limestone, black slate (with subordinate grey slate), and pebbly 

 quartzite. Even in the heart of the division beds of pebbly quartzite 

 are of not infrequent occurrence, and on occasion give rise to 

 massive outcrops. The predominant rocks of the division are black 

 slate and limestone, very intimately associated — so much so that it 

 has been impossible, in many cases, to show them both on the map. 



