342 Ernest W. Skeafs 



with certainty the age of the igneous rocks and their relations 

 to the bedded series. The sharp break between the foliated 

 diabase at the south end of Red Hill and the diabasic fragmental 

 rocks which pass upward into normal Ordovician shales, may be 

 intea-preted as oin unconformable junction of an older series, the 

 diabase, with a younger one largely composed of detritus from 

 it. Even granting the unconformity, the relations might be 

 explained if Lowct Ordovician submarine volcanic tuffs were 

 piled up so that at this place they became sub-aerial and with 

 further eruptions pairt of the material was deposited on land and 

 part falling into the sea near the shore line, became more 

 bedded. Subsequent lateral pressure would impart foliation to 

 the subaerial series and tilt the submarine series at a high 

 angle. The strike of the foliation of the diaibase differs from 

 that of the bedded series, but both dip at almost the same 

 angle, 70 deg.-80 deg. 



An alternative, and, I think, on the whole a more probable 

 explanation, is that the junction between the two rocks at this 

 place is a fault junction. The line of junction runs northerly 

 from here in almost a straight line, and it seems probable that 

 the beds to the west have been let down, a.nd discontinuity 

 produced in what was formerly a continuous series. 



Evidence from the northern part of the district rather supports 

 this hypothesis, for the Dinesus Beds aind also the black cherts 

 (maiking allowances for subsequent alteration) have a strong 

 resemblance to submarine bedded tuffs passing upwai'ds on the 

 cessation of volcanic activity into more normal sediments. The 

 bosses of diabase, diorite, felspar-porphyrite arid micro-granite 

 are somewhat later intrusions from the diabase magma, 

 and in most cases are intrusive into the diabase series. Some 

 part of the acid rocks, however-, come into relation with the 

 clierts and cherty Ordovicians, and, as far ais can be obsen'cd, 

 have not effected any marked alteration of the sediments. In 

 view of their probable comparatively stiperficial origin and low 

 temperature of consolidation, this is not surprising. 



While much of the diabaise was of the character of a tuff, 

 undoubted massive lavas and intrusions occiu-, and if the diabase 

 were pre-Ordovician one would expect in places where the Ordo- 

 vician shore line camo into relation with massive diabases that 



