DETAILED RECORDS. 241 
Feet. 
Hard gray limestone 990-1, 020 
Hard gray sandstone; water 1, 020-1, 024 
Nery hard white gritty limestone 1 , 024-1 , 045 
Soft white sandstone ; water 1 , 045-1 , 060 
w ery har.d white limestone 1 , 060-1 , 075 
Medium hard gray sandstone 1, 07.5-1, 160 
Hard gray limestone 1, 160-1 , 190 
Soft brown shale 1, 190-1, 214 
wery hard white limestone with iron pyrite 1, 214-1, 226 
Soft gray sandstone ; very strong flow of water , 1, 226-1, 234 
Soft brown shale; shells 1, 234-1, 236 
[lard white limestone 1, 236-1, 340 
Drilling stopped by water breaking in at bottom of casing. Rig used, cable. Casing 
feed, 13-inch, 24 feet; 10-inch, 341 feet; 8-inch, 904 feet; 6-inch, 1,330 feet. 
1039. Well near Altyn, Teton Comity. 
[Well begun in June, 1904; drilling stopped March 14, 1905. Authority, W. A. Leonard, driller. Sam- 
ples preserved.] 
This well was put down near the eastern edge of the great series of pre-Cambrian (Algon- 
:ian) rocks, shales, sandstones, quartzites, and limestones that constitute the mass of the 
?ront Range of the Rocky Mountains in the northwest corner of Montana. These rocks 
,re nearly horizontal, but are known to overlie at depth rocks of much later age (Cretaceous), 
his inverse relation being due to a great thrust fault. Seepages of oil at various points 
lave caused many oil claims to be located and have led to some deep drilling. All the 
ocks penetrated by this well arc probably of Algonkian age. 
Record of well 8 miles southeast of Altyn. 
Feet. 
)ark-gray gritty shale. 20- 150 
)ark-gray limestone, sandy from 300 to 350 feet 150- 400 
>ample missing 400- 500 
)ark-gray shale and white limestone _ 500- 800 
jlard black shale 800- 840 
loft gray shale 840- 850 
lard gray limy sandstone 850- 870 
lard brown limy sandstone; slight show of oil 870- 880 
fcample missing 880- 890 
lard dark-gray and brownish sandstone 890- 900 
loft brownish-black sandstone ; a little oil 900- 920 
()ark-gray sandy shale . 920- 930 
loft light-brown limestone and dark-gray shale 930- 965 
Hard black limestone; formation broken, full of crevices 965- 990 
bard dark-gray shale 990-1, 010 
lard light-gray limestone and dark-gray shale 1, 010-1, 040 
lard gray gritty limestone. 1 , 040-1 , 075 
ftard gray and brown sandstone 1 , 075-1 , 085 
flard gray limestone, upper layers gritty 1, 085-1 , 120 
flard gray magnesian limestone and red shale 1, 140-1, 160 
Hard light and dark-gray limestone 1 , 160-1 , 170 
Sample missing 1 , 170-1 , 180 
|4ard light and dark-gray limestone and shale 1 , 180-1 , 190 
o sample 1, 190-1, 200 
edium hard gray sandy limestone 1, 200-1, 220 
Bull. 298—06 16 
