ANALYTICAL ABSTRACTS. 54 1 



The trappean rocks of the district consist of (i) extensive masses, together 

 with many of smaller size, incorporated with the other Huronian rocks, and 

 probably contemporaneous with them ; and (2) dikes which cut through all the 

 members of the series. There are nearly fifty areas of diorite, two principal 

 belts of diabase, and a belt of slaty, greenish diorite, which in places becomes 

 brecciated, and includes fragments, from large boulders down to small peb- 

 bles, consisting principally of quartzites, granites, and syenites. 



Very numerous details are given, which cannot be summarized. 



Comments. — The conclusion of Bell, that the Huronian is divisible into 

 two divisions which are probably unconformable, corresponds with the more 

 recent conclusions of those who have studied the Huronian of the Lake Supe- 

 rior region and the original Huronian of the north shore of Lake Huron. The 

 area reported upon being a continuation of the Lake Huron Huronian, it is not 

 surprising to find the dual character of this series continue. 



No light is given upon the character of the floor upon which the earliest 

 sedimentary rocks must have been deposited. That at several places are 

 found water- deposited conglomerate which bear well-worn pebbles and 

 boulders of granite, syenite, etc., which in one case are said to be exactly like 

 the granite found in situ, seems conclusive evidence that granite and 

 syenite existed in the region in a consolidated condition before the Huronian 

 members containing this detritus were laid down. A part of these conglom- 

 erates clearly belong to Bell's older division of the Huronian, but this series is 

 not divided into formations, consequently we have no information as to 

 whether or not these conglomerates are at the bottom of the series. 



Williams, 2 gives microscopical notes on various rocks from the Sud- 

 bury district. The sedimentary rocks are found to include those which are 

 plainly clastic, those which are clastic but partially re- crystallized, and those 

 which are highly crystalline, but probably derived from elastics. In the 

 last division are placed felsite, gneiss -conglomerate, and gneiss. The erup- 

 tives, including various acid and basic deep - seated and surface rocks, also 

 show extensive metamorphism and re - crystallization. Placed among the 

 highly crystalline rock, probably derived from the elastics, are certain felsites, 

 gneiss -conglomerates, and gneisses. Certain granites, gneisses and schists 

 are of uncertain origin, but give no indication of clastic derivation. 



C. R. Van Hise. 



2 " Notes on the Microscopical Character of Rocks from the Sudbury Mining Dis- 

 trict, Canada," by George H. Williams. Annual Rep. Geol. & Nat. Hist. Sur. of Can- 

 ada for 1889-90, vol. V, Part F, Appendix I, pp. 55-82. 



