222 James Neihon — Old Red and Carboniferous of Arran. 



VI. — On the Old Eed Sandstone and Carboniferous Eocks of 

 the North-east of the Island of Arran. 



By James Neilson, 

 Vice-President of the Glasgow Geological Society. 



{Continued from the April Number, p. 161.) 



IN the Transactions of the Edinburgh Geological Society (vol. v, 

 p. 316) will be found a notice of a section at Lochrim Burn, 

 a quarter of a mile south of Corrie, where is exposed a bed of 

 red sandy shale containing marine fossils. The catalogue contains 

 fifteen species (certified by Mr. John Young, LL.D.), and every one 

 of these is common in the Carboniferous Limestone series of the 

 "West of Scotland. This bed is overlain by another bed containing 

 abundant plant-remains, of which a list of seven species is given. 

 The Bev. D. Landsborough, of Kilmarnock, found here another, 

 viz. Carpolithes sidcatus, L. and H. ("Fossil Flora," pi. ccxx), 

 which Mr. Kidston considers to be characteristic of the Calciferous 

 Sandstone series. It seems to me, however, that the evidence is 

 rather in favour of these beds belonging to the Limestone series. 

 Then, as already noted, there are the fireclays, of which I have 

 observed several distinct beds along the Corrie shore. There is 

 also a bed of fireclay in the old quan*y behind Corrie Hotel (within 

 100 feet of the Productus giganteus limestone) ; this overlies a bed 

 of fine white sandstone. Fireclays also occur in the gap between 

 the northern and the great eastern cliff. 



So far as I am aware, fireclays have not hitherto been recorded 

 from Arran, but they have an important bearing on the question 

 presently at issue. Let us again quote Geikie (pp. 806-814) : 

 " Fireclay or shale, through which rootlets branch freely in all 



directions They appear to be the soil in which the coal 



grew." 



These Arran fireclays differ in no respect, except that some of 

 them are redder or whiter than those I am so familiar with near 

 Glasgow, being crowded with rootlets, while here and there the 

 usual Stigmaria ficoides is to be seen. Some of these fireclays 

 show the peculiar slicken-sides so well known. 



These Eed Sandstone strata not only contain fireclays, but 

 also ironstone, which occurs as nodules (in the fireclays and shales) 

 varying in size from half that of pin-heads upwards to about a foot 

 in greatest diameter. There are also regular bands of ironstone, 

 which may be seen at Corrie, both on the shore and in the old 

 quarries already refei'red to, and also on Maoldon and the mill 

 burn at Brodick. The ironstone is nearly all in the state of 

 peroxide (hematite iron ore), which is doubtless the colouring 

 material of all the red rocks of Arran ; in fact, we have con- 

 cluded that the nodules and possibly the seams of hematite are 

 simply segregated out from the abundance of this material : one very 

 striking instance being; that of a nodular band about one inch thick 





