Like the cliffy limestone member it represents a periodof lagoonal and carbonate bank deposition. The terrigenous beds of the u p p e r solution zone may reflect earlypulses of the regional uplift that occurred prior to deposition of the overlying Amsden Formation

T h e Bull Ridge contains a limited fauna of corals (Syr-ingopora, Diphyphyllum, Canadiphyllum?, a n dVesiculophyllum), brachiopods, and foraminifers of earlyMeramecian age

Bull Ridge Member — The highest member in theMadison Limestone consists of cliffy, medium- to thick-b e d d e d cherty limestone that overlies a t h i n - b e d d e ddolomitic siltstone and shale interval (upper solutionzone) which is brecciated at some localities. The memberis 85 to 100 feet thick in the Beartooth segment of theWyoming Province; the solution zone at its base is about30 feet thick. Like the cliffy limestone member, the limestone beds of the Bull Ridge consist of bioclastic debrisin a fine-grained matrix. Brecciation of the limestonesrelated to post-Madison karst development is a commonfeature, and red sand, silt, and clay from the overlyingAmsden cycle is present in sinkholes and solution cavities

The cliffy limestone member represents a short period of evaporite deposition in a lagoonalenvironment followed by carbonate deposition on shallowoff-shore marine banks

At the base of the cliff-forming unit is a solution breccia(Figure 5) about 15 to 35 feet thick that r e p r e s e n t s aleached interval of evaporites, carbonates, and terrigenoussediments (lower solution zone

mainly crinoidal)in a micrite matrix. A moderately diversified fauna ofbrachiopods (mainly large spiriferoids), corals (Syr-ingopora, Vesiculophyllum, Homalophyllites), a n dforaminifers indicates an Osagean age.

Cliffy limestone member— This member consists predominantly of cherty, medium- to thick-bedded limestoneabout 160 to 175 feet thick that forms prominent cliffsa n d flatirons t h r o u g h o u t t h e area s t u d i e d . At somelocalities many of the limestone beds are partly or completely dolomitized. The limestone consists principallyof commonly oolitic bioclastic debris

The cherty dolomite member appearsto represent a restricted marine facies, perhaps lagoonalin origin. Extensive brecciation and shattering may bethe result of leaching of thin evaporite beds throughoutthe sequence. The age of the member is Osagean by virtueof its position above and below beds dated paleontologi-cally as Osagean

Fossilsare rare; the fauna consists of a few scattered solitary coralsand brachiopods

Cherty dolomite member — Above the Woodhurst isa cherty carbonate sequence about 185 to 225 feet thickthat consists mostly of dolomite and dolomitic limestoneand subordinate limestone beds

T h e Woodhurst is interpretedas an alternation of shallow-water off-shore marine limestone and shoal-water limestone periodically interruptedby minor influxes of terrigenous sediment

Cottonwood Canyon Member—This member consistsof interbedded quartzose shale and mudstone and quartzsiltstone from about 40 to 50 feet thick. It was studiedat only two localities (sections 1 and 5)

at section 5 it consists of cherty, thinb e d d e d dolomitic limestone and dolomite (Figure 3).Megafossils are rather rare in the dolomite member; thefauna consists mainly of corals (Vesiculophyllum, Syrin-gopora, Cyathaxonia, Zaphrentites?), small brachiopods,and conodonts of Kinderhookian age (Siphonodella cre-nulta Zone). These fossils are more abundant at the morenorthern localities. The lower dolomite member appearsto represent a dolomitized shoal-water sediment that wasdeposited in clear waters that d e e p e n e d northward.

T h e Woodhurst contains an abundant faunathat consists principally of corals, brachiopods, and gastropods; foraminifers and conodonts are also present. Burrowing and bioturbation by benthonic organisms is a dis-

tinctive feature. The fauna includes the corals Rylstonia,Michelinia, Lithostrotionella, Vesiculophyllu,Homalophyllites, and Zaphrentites mainly indicative ofOsagean age