442 DALE— CAMBRIAN MANGANESE DEPOSITS OF [April 25, 



Early Cambrian Physiography. — In all probability the area 

 occupied by Trinity, Conception, Placentia, and St. Marys Bays, the 

 included land and the western and eastern margins including the 

 present known Cambrian outcrops, was a continuous body of water 

 shortly after the beginning of the Cambrian transgression. West 

 and east of this Cambrian sea were high and extensive pre-Cam- 

 brian land areas. The great crustal movements which threw the 

 pre-Cambrian into mountain ranges probably converted the portion 

 now occupied by the four bays and adjacent land into a narrow 

 basin. The main topographic features of the southeastern part of 

 Newfoundland during the beginning of the Cambrian were two land 

 areas of great relief separated by a comparatively narrow trough 

 which had a general north-south direction. 



Whether this trough was a closed one or not, it would be difficult 

 to prove, but from the requirements of the problem it is necessary 

 to postulate a more or less closed basin or coastal shoals or lagoons, 

 Concentration of manganiferous soluble salts could go on satis- 

 factorily only in a more or less restricted shallow sea where the 

 water was comparatively quiet. The facts that ripple marks occur 

 occasionally in the deposits such as at Manuels and that a shallow 

 water fauna abounds such as trilobites are sufficient indication that 

 there was a shallow sea at this time. 



Nature of Deposited Sediments. — Into this trough during 

 early Cambrian times great quantities of mud were brought by rivers 

 draining the pre-Cambrian land masses and to a lesser extent by 

 the action of the waves on the shore line. As has already been 

 stated the greater thickness of shales in the western portion of the 

 basin is due to the fact that sedimentation had been going on for 

 a longer time in that part of the basin which was in all probability 

 the deeper part. It is also quite possible that the western parts of 

 this trough were receiving more sediments than the eastern. The 

 shales are characterized by their predominant red color in the 

 western parts of the basin interbedded with shales of green color 

 and throughout the entire area by a highly manganiferous zone. 



Genesis of the Manganese Ore. — The distinctly bedded char- 

 acter of the manganese deposits and their occurrence in definite 

 horizons of limited thickness and considerable horizontal range seem 



