TWO '^ SLATE CONGLOMERATES." 89 



beds of coarser quality pebbles of red or gray syenite occasionally occurred; small red 

 jasper pebbles were observed in one or two places, imbedded in wbite quartz rock, 

 but they were by no means numerous, and were confined to the upper portion of the 

 formation. Some of the quartzose sandstone beds were of a deep orange red, but 

 this seldom extended far. The slates were gray, green or blackish in color, and were 

 usually more or less silicious, and frequently very micaceous. Some parts of the 

 formation, being the more schistose portions, were almost exclusively composed of 

 mica, generally of a gray color, but sometimes tinged with iron-brown, and the par- 

 allel layers into which the rock was divisible presented on their surfaces small, sharp 

 corrugations. Some parts were marked by small shining specks of chlorite, and, in 

 some places, the slates contained imperfect crystals of epidote, occasionally arranged 

 along planes of the bedding, but more frequently along cracks or joints. In these 

 epidotic slates the prevalent color of the rock was gray, and the epidote a dingy 

 brownish green and sometimes disseminated, gave to smooth weathered surfaces the 

 appearance of belonging to a slate conglomerate." 



So much, touching the slates, evidently relates to the lower portion of the 

 formation holding what was afterward called the "lower slate conglomerate." 

 But the following clearly relates to the " upper slate conglomerate " : 



" The more purely argillaceous portions of the slate were generally black, or of a 

 very dark brownish tinge, and, in these, a very symmetrical jointed structure, divid- 

 ing the rock into rhombohedral forms of considerable regularity, was frequently 

 recognized. The slates were very often observed to pass into a conglomerate holding 

 pebbles of granite or syenite chiefly, varying in diameter from an eighth of an inch 

 to a foot, and imbedded in a black argillaceous matrix. The limestones observed, 

 though of minor importance as regards thickness, were of a marked character, and in 

 most respects bore a strong resemblance to those found associated with the quartz 

 rock formation at the western end of the north shore of Lake Huron. They consisted 

 of calcareous beds of a dark-blue color interstratified with layers in which lime appears 

 to be altogether absent, the composition of these being almost purely silicious or ar- 

 gillaceous. The outcropping edges presented alternations of thin, sharp ridges and 

 grooves." 



Mr. Murray, in review, makes enumeration of the following constituent 

 members of the series (p. 39) : 



Pure massive beds of white, associated with thin beds of gray quartz rock 

 and beds of greenstone, underlaid by less massive beds of greenish white, 

 gray and red quartz rock, sometimes of a slaty structure, which, in all, 



amount to a thickness of about 4,000 feet. 



Black argillaceous slates and conglomerates, with syenitic pebbles 800 " 



Limestone band . 500 " 



Micaceous slates, interstratified in parts with gray quartz rock, all the 

 lower visible portions near the granite consisting of chloritic and epidotic 

 greenstone 5,140 " 



Mr. Murray does not estimate the thickness of the lower member by itself, 

 but he states that "the total thickness can scarcely be less than 10,000 feet." 

 The formation thus described lies along the valley of Spanish river. 



