246 REPORT UNITED STATES GEOLOGICAL SURVEY. 
Section on Bull Lake Fork. 
No. 1. Archean. 
No. 2. Primordial quartzitic sandstone. 
No. 3. Quebec limestone formations. 
No. 4. Buff or drab reddish stained limestones, apparently fonning a 
distinct horizon underlying the buff magnesian limestone, as seen in the 
great cliff exposures in the cafion walls. This limestone holds the hori- 
zon of the Niagara, but it is regarded as probably belonging to the Car- 
boniferous. 
No. 5. Carboniferous magnesian limestone, 300 feet, +. 
No. 6. Drab and gray rusty-weathered limestones, more or less cherty, 
with magnesian layers 400 feet +. Contains characteristic Carbonif- 
erous fossils, and is here referred to the lower division of the series of 
which it forms the upper member. 
No. 7. Middle Carboniferous division, light gray, reddish buff, weath- 
ered, even-bedded sandstones, 400 feet, +. 
No. 8. a, buff or light-gray limestones, with occasional shaly layers 
and bands of chert, with calcite and gypsum, 40 feet, +; b, chert 
band with fibrous gypsum, 4 feet; c, gray limestone, with cherty layers 
in middle containing nodules of chalcedony with a black bitumen min- 
eral and calcite geodes, 15 feet, +; d, dark and light-gray limestones, 
cherty and nodular, alternating with shaly layers, with a 6-inch layer 
charged with black bitumen or carbonaceous matter, contains obscure 
fossils, 15 to 20 feet ; e, gray limestone, with calcite, 8 feet. 
No. 9. Drab clays and brown indurated shales, 50 feet, +. 
No. 10. Gray magnesian (?) limestone, with calcite 15 feet, +. 
No. il. a, gray nodular limestone with clay partings, and chert, nu- 
merous fossils of same species occurring in No. 14, 35 feet, + ; b, blue 
nodular limestone and shales underlaid by indurated dark drab calea- 
reous Shales containing cavities lined with calc. spar, 40 feet, +. 
No. 12. Chert band, made up of uneven layers, 8 feet, +. 
No. 13. Gray limestone, in places brecciated, with flint nodules, con- 
tains Chetetes (?) Bryozoa, &c., 20 to 30 feet. 
No. 14. Permo-Carboniferous horizon; a, light-drab clays with nod- 
ules of fiint and calcite, and thin layers of gritty brown and gray lime- 
stone containing casts of a small Plewrophorus, Bakevillia, &e., and in 
lower part thin irregular layers of limestone alternating with clays con- 
taining numerous fossils, Productus costatus ? P. punctatus (2) Spirifer, 
two species, &e¢., 65 to 70 feet; b, gray, thin-bedded, gritty limestone, 
more or less coneretionary and magnesian (?) with ripple markings, 25 
feet + ; dip 15° to 20° northeast. 
No. 15. Light-drab clays with thin indurated layers, imperfectly ex- 
posed, 30 to 50 feet. 
No. 16. Triassic red sandstones and arenaceous shales, with thin gray 
sandstone layers 1,000 to 1,400 feet; dip to the northeast, and at angles 
of 15° to 20°. 
No. 17. White gypsum, more or less regularly bedded, including one 
or two thin layers of sandstone, the outcrop somewhat fractured by ten- 
dency to joint structure. This bed shows a thickness of 25 to 40 feet, 
forming the crest of an outlying spur-ridge in the north side bluffs, some 
distance above the head of Bull Lake. : 
No. 18. a, red, greenish, and chocolate-colored shales with thin layers 
of white gypsum, and gray and drab indurated layers; b, red and gray 
banded shales, the outcrop presenting a beautifully variegated band 
wherever seen, 100 feet, +. 
No. 19. Drab, fragmentary limestone, 6 feet, + ; dip 23°, N. 42° H. 
