fRiNDLE.] GEOLOGIC SKETCH. 
Provisional tabular statement of Yukon stratigraphy. 
25 
Age. 
Formation name. 
Contact relations. 
Lithologic character. 
f Alluvium 
Flood-plai 1 1 dep< tsits. 
Fresh-water silts, sands, and 
gravels. 
Sands, clays, and gravels. 
Fresh-water sandstones 
Quaternary 
Post-Eocene: 
Tertiary 
1 Yukon silts 
Unconformity . 
(?) 
(?) 
Conformity?-.. 
(?) 
Conformity - - 
Unconformity. 
do .... 
Eocene _ . 
Kenai forma- 
tion. 
Upper Creta- 
ceous. 
Lower C r e t a - 
shales, and conglomerates. 
Fresh-water and marine sand- 
stones, shales, arkoses. and 
conglomerates. 
Fresh-water calcareous sand- 
ceous. 
Do 
stones. 
Marine, black, slaty shales, 
and thin-bedded limestones. 
Marine, massive, white lime- 
Permian 
Mississippian .. 
stones, heavy conglomer- 
ates, and gray shales. 
Marine, black slates, and thin- 
Devonian 
Pre- Devonian . . 
Do__ 
Rampart for- 
mation. 
Forty mile for- 
mation. 
Birch Creek 
schists. 
Pelly gneiss - . 
(?) 
Unconformity _ 
Conformity . - - 
Unconformity 
bedded limestones. 
Volcanic material, interbed- 
ded with limestone, slate, 
etc. 
Schists and crystalline lime- 
stones. 
Quartzites and schists. 
Gneissoid and schistose gran- 
ites. 
Archean? 
The region visited by the writer is largely occupied by the meta- 
morphic sediments called in the table the Birch Creek schists and the 
Fortymile formation, by the Devonian rocks (Rampart formation), 
by igneous intrusions, by Tertiary sandstones and conglomerates 
(Kenai), and by the Quaternary deposits. These formations will 
therefore be described, but the Carboniferous and Mesozoic horizons, 
which have not been studied by the writer, will receive no further 
consideration. 
GEOLOGIC MAP. 
Though much of the Ynkon-Tanana country has not been sur- 
veyed in detail, yet the general facts of rock distribution indicated 
on the accompanying map (PI. IV) are probably correct. The writer 
is only responsible for the geology of the central part of the area, thai 
along the Yukon being based on Collier's work, while the southeast- 
ern and southwestern parts are based on the Brooks surveys. 
It is of interest to note the general facts of distribution. A broad 
belt of gneisses and schists, termed the Pelly gneisses, stretches north- 
