ry ▁by ▁D . B . ▁Dow ling ▁in ▁ 1 9 0 0 . ▁ ▁Lith ology ▁ ▁Sub div isions ▁ ▁The ▁St ony ▁Mountain ▁Form ation ▁is ▁divided ▁in ▁the ▁following ▁sub - un its : ▁ ▁South ▁( Will ist on ▁Bas in ) ▁Pen it enti ary ▁Member : ▁arg il lace ous ▁dol om ite ▁G unn ▁Member : ▁inter bed ded ▁cal care ous ▁sh ale ▁and ▁foss il ifer ous ▁lim estone ▁North ▁Gun ton ▁Member : ▁cry st all ine ▁dol om ite ▁Lower ▁St ony ▁Mountain : ▁arg il lace ous ▁dol om ite ▁ ▁Distribution ▁The ▁St ony ▁Mountain ▁Form ation ▁occurs ▁throughout ▁the ▁Will ist on ▁Bas in . ▁It ▁reaches ▁a ▁maximum ▁thick ness ▁of ▁ ▁in ▁the ▁sub - sur face ▁at ▁the ▁Canada / Un ited ▁States ▁border , ▁and ▁th ins ▁out ▁towards ▁the ▁east , ▁north ▁and ▁west . ▁In ▁Man it oba , ▁where ▁it ▁is ▁exposed ▁at ▁the ▁surface ▁in ▁the ▁er os ion ▁bel t , ▁it ▁has ▁a ▁thick ness ▁of ▁. ▁ ▁Rel ations hip ▁to ▁other ▁units ▁ ▁The ▁St ony ▁Mountain ▁Form ation ▁is ▁slightly ▁un con form ably ▁over lain ▁by ▁the ▁Stone wall ▁Form ation ▁and ▁sharp ly ▁over l ays ▁the ▁Red ▁River ▁Form ation ▁or ▁the ▁Her ald ▁Form ation . ▁ ▁References ▁ ▁Category : Str at ig raph y ▁of ▁S ask atch ew an ▁Category : Str at ig raph y ▁of