THE BANNOCK OVERTHRUST 691 
UPPER MISSISSIPPIAN 
FEET 
Limestone, earthy with chert in irregular concretions and streaks 
parallelstoubed ding iu iccieh ise tel ee eRe AO Tel eon LCG a 20 
Limestone, light gray to whitish, thin-bedded; fossil collection ror... 46 
Sandstone, white, calcareous, bears large Zaphrentoids............... 14 
Limestone, dark gray crinoidal, includes a Martinia horizon, about.... 100 
Shalevand'reddish quartzite fragments,.about. 20) .....0...-....... 30 
Quartzite, whitish, outcrops small and scattered, bears small 
LO SORA GIUS & Sid tie StS to ee ees Re Re 270 
Conceal CU es yar ccs apaarors soi aie en a ret ne Nee are 200 
Limestones, gray, in 1- to 3-foot beds, fossil collections.............. 450 
Base of upper Mississippian not exposed. 
Thickness of upper Mississippian exposed 
Ato calitlaickmessrOlsSECtIOM sis. sees cists cis nts ae a. s aeed wis ashes as 3,530 
It will be noted that in this section it is possible to subdivide the 
Wells formation into three portions, an upper calcareous sandstone 
or siliceous limestone, a middle sandy series, and a lower sandy 
and cherty limestone series, the lower two of which, however, do 
not correspond with the Weber and Morgan formations in Weber 
Canyon, Utah. Dr. Girty has recently reviewed the section at the 
latter locality and states that-the order of lithologic succession is 
quartzite, calcareous sandstone, and red quartzite. 
The variations which occur in the three portions of the Wells 
formation have been studied throughout the general area under 
discussion and in brief are as follows: 
The upper limestone ranges from a maximum thickness of 75 
feet down to a feather edge. It consists of a dense gray calcareous 
sandstone grading locally to siliceous limestone, which weathers 
into white massive beds that are topographically conspicuous as 
cliff makers. Bluish-white chert occurs in it in bands 2 inches 
to 1 foot thick and locally in ovate nodules. ‘Toward the base the 
chert becomes more nodular and darker. Silicified fragments of 
brachiopods project in little crescents from the weathered surfaces 
of the limestone. This member is usually sparingly fossiliferous 
but, in the vicinity of Swan Lake, Dr. Girty reports a limited 
fauna (12a). 
