PETROGRAPHIC GEOLOGY AND DESCRIPTIONS. 371 



Shale. Slate.] 



this conglomerate. The finest part of the cement is apparently a consolidated kaolinic 

 mud. The entire thickness is probably about 100 feet. 



No section. 



Age. Basal conglomerate of the fragmental Keweenawan (Puckwunge). 



Remark. This conglomerate was struck in the deep well at Short Line Park, 

 where it lies below a considerable thickness of " gabbro," and is interbedded with 

 eruptive rock, some of which is apparently amygdaloidal. The age of this conglom- 

 erate is considered in vol. iv, page 567, also in this volume at page 54. N. H. w. 



No. 450. SHALE. ( 'Greenish. ) 



S. E. 14 S. E. 14 sec. 2, T. 48-16 W. North bank of St. Louis river. Underlies conformably No. 449. 

 Ref. Annual Report, x, page 12. Same as No. 1974. 



Meg. A soft, very fine-grained greenish gray shale, quite similar to No. 447. 

 When scratched with a knife blade a buff-color streak is left. There are a few 

 brownish rusty areas, probably from the decay of pyrite, as a small pyrite grain is 

 seen in the center of one of these areas. 



No section. 



Age. Archean (Keewatin). u. s. G. 



No. 451. SHALE. 



Same place as No. 450. The bedding dips southwest about 4. 

 Ref. Annual Report, x, page 12. 



Meg. A soft, purplish-gray shale or slate having a rough, imperfect slaty cleavage 

 which crosses the bedding of the rock at an angle of about 70. The bedding of the 

 rock is well exhibited by bands and lamina? of different color. This rock is in general 

 the same as Nos. 447 and 450. It has some greenish-gray blotches and streaks. 



No section. 



Age. Archean (Keewatin). u. s. G. 



No. 452. SLATE. ("Pencils.") 



Same place as No. 450. 



Ref. Annual Report, x, page 12. 



Meg. Rock essentially the same as Nos. 447, 450 and 451. It breaks into long, 

 rough prisms having a rhomboidal cross section. The two specimens preserved are 

 about five inches long and usually less than a half inch in width. 



No section. 



Age. Archean (Keewatin). u. s. G. 



No. 453. SLATE. (Black.) 



Lower falls of the St. Louis river; S. E. ^ sec. 10, T. 48-16 W. 

 Ref. Annual Report, x, page 12. 



