374 Reviews — The ArbovAoi Copper Mines at Cardross. 



west, with its downthrow side to the north, and these movements are 

 correlated with the Middle Ordovician disturbances of Scotland and 

 North America. The Upper Series derived its material from the 

 highland south of the fault, which was a pre-Cambrian area, in part 

 belonging to the land barrier, with remnants of the lower dolomite- 

 bearing series. 



The tillites occur at two horizons. The lower is a local deposit 

 resting upon a grooved j^avement, and containing ice-scratched 

 boulders of gneiss, granite, and sandstone. Associated con- 

 glomerates contain pebbles of "chert, and dolomite with oolitic and 

 stromatolitic structures. The upper tillite contains ice-scratched 

 boulders, but is of a different character ; it is of very even thickness, 

 extends over a wide area, and passes downwards into the even- 

 grained ungrooved sandstones beneath, thus indicating a glacial 

 deposit laid down under water from floating ice. The lower tillite, 

 on the other hand, is of a continental type. 



Dr. Holtedahl refers the tillites to some period between the Lower 

 Ordovician and Upper Silurian, and lays stress upon the fact that 

 they do not necessarily indicate a climate as cold as that of northern 

 Norway at the j)resent day. It is to be hoped that fossils will soon 

 be found in these beds, and their exact age established beyond doubt. 

 Their non-discovery uj) to the present is not incompatible with the 

 age postulated, for considerable thicknesses of the Durness Limestone 

 are barren, and limestones of undoubted Cambro-Ordovician age 

 in North America of the same petrographical character have failed 

 to yield fossils. Dr. Holtedahl's researches indicate that the tillites 

 were formed before the Caledonian deformation attained its - 

 maximum, which was in Lower and Middle Silurian times, and that 

 no general climatic change is to be inferred from them. 



L. Hawkes. 



TfiE Arbouin Copper Mines at Cardross. By L. C. Ball. 



Queensland Geological Survey, Publication No. 26L pp. 69. 



Brisbane, 1918. 

 rpiIE Arbouin Copper-mines are situated in North Queensland, 

 -^ about 20 miles west of Mungana, the terminus of the Chillagoe 

 Railway. Geologically the Cardross district is composed entirely of 

 pre-Silurian schists and gneisses, and only to the east, about 

 Mungana, are these overlaid by Silurian shales and limestones. 

 The schists and gneisses have been invaded by an old series of basic 

 dykes, now in the condition either of amphibolites or diorites, and 

 later, probably at the time of the intrusion of the Permian granites 

 by pegmatites and elvan dykes, accompanied by metalliferous 

 lodes. 



There are several belts of mineralization, and the trend of these 

 and of the individual lodes is about north-east and south-west. 

 The elvans, though having a trend generally at right angles to the 

 lode direction, are evidently closely connected with the ore bodies, 



