46 Cu DAKE 
Fort Union( ?).—Since there is some uncertainty as to the age 
of the formation described under this name, and since upon this 
formation more than on any other depends the dating of the fault 
in question, it seems worth while to give a detailed description of 
its relations and lithologic character. 
TABLE I 
TABLE OF FORMATIONS 
. 98 Thickne 
System Formation Characteristics aa "Eee 
Quatennany eee |e een Glacial till and terrace gravels ? 
Mertianyer ioral tetcruce cate spen tens Andesitic breccias and lavas ? 
Cretaceous or 
Tertiary....| Fort Union(?) | Buff to yellow sandstones, conglomerates, 300-++ 
red and gray shales 
Codyeee een se Gray to black shale, sandy near top 2,000 
Bromblersears nie Gray sandstones and shales, with ben-| 500 
tonite 
Cretaceous... .|{_ Thermopolis 
-and Mowry..| Gray and intensely black shales, with| 900 
sandstone and bentonite 
(Cloverly........| Gray cross-bedded sandstone and shales} 110 
Jurassic or 
Cretaceous..| Morrison...... Variegated red, gray, maroon (etc.), 500 
shale, and sandstone 
jurassic Sundance...... Greenish-gray shales and sandstones and| 500 
thin fossiliferous limestones 
Permo-Trias...| Chugwater.....| Red sandstones and shales with gypsum| 750 
imalbateaerc see Massive gray limestone. 100 
Tensleep...... Massive gray sandstone and brown 100 
Carboniferous.. quartzite 
Amsden....... Red shale and red to gray limestone 150 
Madison.......| Massive gray limestone, conglomeratic] 1,000 
at the base in places 
Ordoviciana | Bighormesn se Massive gray limestone 300 
Cambrian.....| Deadwood.....| Conglomerates, sandstone, and limestone 800 
iBre-Cambriany| sae eerie Red granite, gneisses, and schists ? 
It consists of an unmeasured thickness of alternating beds of 
yellow sandstone with red and white or gray clays. 
The sandstones 
vary from buff to bright yellow, and occur in several beds from 2 to 
20 feet thick. They are cross-bedded on a large scale, and contain 
many concretions of brown sandstone varying from a few inches up 
to 10 feet or more in diameter. The concretions are harder than 
the matrix and weather out in large numbers, occurring abundantly 
over the surface of the ground. At many places the sandstones 
are finely conglomeratic, the pebbles averaging between one-fourth 
