T1IK AIICH. KAN I;o< KS 17 



The (Jrampiau Series of Eastern Islay comprises the following 

 UK -inhere in descending order : 



4. Islay limestone. "I _ 



Slack slates and phyllites j = Ballachull8h Intone and slates. 



J. I'hyllites with thin quartzose bands (=Striped Series). 

 1. Quartz-schists ( = Appin quartzite). 



This series is overlain unconformably by quartzites and shale** 

 which greatly resemble those of the Cambrian in Skye, but as no 

 fossils other than worm-tracks and annelid -bur rows have been found, 

 the correlation is not proved. These newer quartzites liave a con- 

 glomerate at the base which contains pebbles of all the older rocks 

 in the island, and includes many of the Islay limestone. 



In Islay, therefore, not only is the Grampian Series brought 

 into apposition with Hebridean and Torridonian rocks, but there 

 is evidence which amounts to a strong presumption that it is of 

 pre-Cambrian age. It is, moreover, a noteworthy fact that nothing 

 comparable to the Moine Series has been found in the island. 



The Geological Survey has not yet ventured to record any 

 definite conclusion with respect to the relative ages of the Moine 

 schists, the Torridonian, and the Grampian Series. In the absence 

 of any official declaration it is only possible to indicate the tn-ml 

 of the evidence, so far as it has been published in the Report* 

 and Memoirs of the Survey. Reviewing this evidence one cannot 

 fail to be struck with the fact that on the western side of the 

 great thrust-planes, where the succession is clear and post-Cambrian 

 disturbance is 'small, only two Archaean Series are found, i.e. 

 the Hebridean and the Torridonian. On the other hand, in the 

 much larger area to the eastward there are at least three such 

 series, Hebridean, Moine, and Grampian ; further, it seems very 

 probable that both of the two last are newer than the Hebrideau, 

 and also that both are pre-Cambrian, but the relative age of the 

 Moine schists is still a matter of doubt 



Two alternatives present themselves, either (1) the Moine Serin 

 may be a separate intermediate system, or (2) they may be n 

 sheared and metamorphosed Torridonian deposits of the Skye 

 facies. 



If they are to be regarded as a separate Meearduean s. 

 (either with or without the Grampian Series), two awkward 

 questions have to be answered, (a) what has become of the 

 Torridonian strata east of the Moine thrust ? and (6) why is there 

 nothing in the western, except the Torridonian, that is comparable 

 to the Moine schists ? The evidence recently disclosed enables us 

 to assume that the Moine schists were originally a series of 



