I'JUU 



iiart2' cAunoMi i;u«n s li niksionk or s. walks ( oai.fi i;i,i». 1-1 



At till- Wfstcrn »'n<l nf tlic district li.-iv (l«'alt with, annuid 

 l{utliiii. l\'nlliiu*, ami Llansannor, i\\v total thifUness of the C'ar- 

 hoiiifi'ious Limestone Serit-s probaldy apin'oxiiuatos to 27'iO fivt, 

 made uy a> follows : 



U (D, and (r) D., in part 



S- ""'" ^Miiin Liiin-sione. 



c,+s, 

 c; .. 



j^ ^ (rj^oO Lower Limestone Shal. 



Total .i7r)0 



The thickness here assigned to K is conjectural. The otlier 

 lii,'nres may be regarded us fair approximations. A cover (.f Trias 

 conceals the junction of the Main Limestone with the Millstone 

 Orit. I) has n(>t been ree»)gni/ed, and, if rejjresented, it is most 

 probably incomplete. The Lower Limestone Shales, in so far as 

 thev are exposed, jnvsent a normal facies of limestones and shales. 

 The Main Limestone is com])osed essentially of undolomiti/ed 

 crinoidal limestones and oolites, with a standard fauna. The 

 upper ijjirt of S,, however, shows the lagoon-phase dejiosits which 

 are so characteristic of that horizon ^ over most of the South- 

 western Province; and eontem])or.ineous (lolomitizati«»n of the 

 limestone is imj)ortant at two levels: (I i in Z, and (2) in ('-the 

 Lfiminoau Dolomite. A Mfnlio1n i)hase at the base of C..«letected 

 at Miskin, about 1- miles away to the ea>t, may be )»resent. but has 

 not bt-en ])roved. 



At the north-eastern extremity of the area liere described, that 

 is, in the Kbbw valley at Hisea, the total thickness is reduced to 

 about S(X) feet, made u)* as follows : 



C.-I-Si] /•''•''. 



C* L C)?.") Main Liniestone. 



z' J 



j( \'l't Lower LiniGHtone Shales, 



Total ^"'" 



There the Main Limestone is almost wholly d<.lomitii-. It- lower 

 iM)rtion, alwrnt 1(K) feet thick, consists entirely of crystalline <lolo- 

 mites representing,' contemporane<»usly-alteri'd standard limestones, 

 in which occasional erinoi<l-ossicles are pnictically the only 

 stirvivini; fossils. Its upper jjortion. about ^T') feet thick, is 

 composi'd almost wholly of dolomite-mudstones with intercalated 

 bands of crvstalline dolomite. b\it includes a very small thickness 

 of calcitic oolite and calcite-mudst«»ne near the summit. In this 

 u|)per iM»rtion, the d(domitie beds are barn-n, but the calcitic betls 

 e<»ntain ostnic«)ds and foniminifeni : this is essentially a thick 

 Moilinlii phase. eharaeteri/e(l by a i,Mvat develoi>ment of dolomite- 



' K. E. L. hiv.n (H.w.T |.a|MT. |.. .M L 



