[kï^ele] mesozic clays and sands 



31 



A smaller deposit of the same type of sands occurs a short distance 

 below the foot of Long Portage on Mattagami river, in the bank over- 

 lymg the fire-clay beds. The deposit, which is enclosed in boulder 

 clay, IS limited in width but is about 40 feet thick. The sands are 

 arranged in beds sloping down stream and contain a band of grey and 

 yellow clay about a foot thick. Above the clay bed the materials 

 are yellow gravels and cobble stones. The orange sand and gravels are 

 overlaid by grey fluvio-glacial gravels with included lenses of boulder 

 . clay A solid mass of hard, grey, gritty till carrying unusually large 

 boulders, caps the bank. 



The largest deposit of orange sands in the region occurs on the 

 east bank of Abitibi river between Sextant Portage and the head 

 of Long Rapid. 



The sands here are about 30 feet thick and extend for a mile along 

 the banks under a capping of boulder clay. The sands are composed 

 almost exclusively of coarse, angular to round quartz grains, some- 

 times running as coarse as fine gravel. Angular fragments of dis- 

 integrated pre-Cambrian schist are mixed with the sand toward its 

 base. The bottom of the deposit lies below water level and was not 

 seen. 



The place in the geological sequence to which these sands should 

 be assigned cannot be easily fixed. It is difficult to regard them as 

 pre-GIacial in view of the accepted theories regarding the scouring 

 action of a continental glacier like that which passed over this region 

 Friable, unconsolidated deposits like these sands would seem to have 

 small chance of surviving such a glaciation. On the other hand 

 we are confronted with the strongly oxidized and residual character 

 of the materials in the deposits, and their freedom from glacial dirt 

 of any kind. If it is urged that the lack of cementing material would 

 indicate a recent origin it may be pointed out that there are sandstones 

 of Silurian age on Abitibi river with no greater measure of cementing 

 material present. 



It would appear that their comparative freedom from materials 

 other than quartz would give these sands economic value as a source 

 of sihca. It is probable that they contain too high a percentage of 

 iron to be used in glass manufacture although washing would no 

 doubt reduce this. As the texture of the sands is about right for glass 

 making purposes a few washing trials and chemical analyses would 

 settle the question. There are no sands so pure as these in the Glacial 

 series. 



