* 104 

 TABLE OF FORMATIONS. 



1. Quaternary Sands and gravels, 



stratified clay, 

 boulder clay. 



2. Ordovician-Farnham Black slates, 



conglomerate. 



3. Cambrian-Sillery Red and green slates 



and sandstones. 



LTslet Quartzose, grey schists 



and quartzite. 



4. Pre-Cambrian ? Porphyries and green- 



stones. 

 Intrusives — Post-Sillery ; in part, 

 at least, later than Ordo- 



vician — Thetford series.. . .Peridotite, altering to 



serpentine, pyroxenite, 

 gabbro, diabase, por- 

 phyrite, granite and 

 aplite. 

 Post-LTslet — Broughton 



series Serpentine, soapstone, 



greenstone schists. 



THETFORD SERIES. 



The rocks of the Thetford series make up the greater 

 part of the serpentine belt. In this district they extend 

 southwesterly from Broughton mountain, in the township 

 of Broughton, through Thetford, Coleraine, Ireland, 

 Wolfestown, and Garthby townships to Big Ham mountain. 

 After an interval of 4 miles (6-4 km.) they reappear in 

 Little Ham mountain, and continue in a southwesterly 

 direction to Danville, and thence to the St. Francis river. 

 Diabase covers the largest area of any rock of the series, 

 peridotite and serpentine the next. Gabbro and pyroxenite 

 also form considerable masses, while granite and aplite are 

 of relatively small extent. 



Peridotite and Serpentine. — Serpentine forms the 

 country rock of all the mines, and, with less altered perido- 

 tite, makes up many of the larger hills in the mining 

 district. The hills near Little Lake St. Francis, near Black 

 lake, in the southern part of Ireland, and between Belmina 



