part 2' cAHnoMi i:iMi N mmhsthnk <»r s. wai-Ks comj iki.d. \'2'> 



Kast of tlie Taff. 



A twofold division of tlio Lower Liiiu'stoiie Shales, un lithological 

 irrounds, was estaMisliod by Dr. A. Stralian in this outcrop, and 

 represented uj)on tlu' ( i(M(l(io^ifal Survey inaj)J Our own oliscrva- 

 tions lead us to reeo;4;nizi' three divisions. 



Lower Limeetone Shales between the Ebbw and the Taff. 



Geological Sikvey. Present Classification-. 



■hales with thin bands 

 and nodules of linie- 

 citone. 



in( tidal limestono, 

 often oolitic. 

 Lower Limestone.) 



'.i. shales witii tliui 

 limestones. 

 50 to 100 feet. 



K ,. Subzoiie nt >itinj'u-in(i 

 orfopliratu (J. de C. Sow- 

 er by) mut. /3 Yaughan. 



2. Crinoidal limestone 

 and oolite, 

 to to 100 feet 



K, or K_. 



1. Limestones and 

 shales. 

 30 to (r) 60 feet. 



Kj. — Snbzone of Productxii>\ 

 bdissiis Vanghan. 



Our lower division (1) consists mainly of limestone in the Ebbw 

 valley, but includes almost as much shale as limestone in the 

 TafF valley. A })artial establishment of J/o^//V;/r/- phase conditions 

 is indicated by several features of this lower <^roup, namely, 

 seams of caleite-mudstone with Srrpiihi. limest^incs of o-ty|)e,- an<l 

 limestones with a mixed fauna of erinoids, brachiopods, ostracods, 

 and thin-shelled lamellibrauehs. 



The famias of om- lower and u]>per divisions (I v'c ^i) wan-ant 

 the refen-nee of these two i^roups to K, and K,^, respectively, but 

 the scanty faima of the middle i,n'(»u|) of limestones (2 ) affords 

 no i^rounds for correlation with one sub/one rather than the other. 

 It is interestiuiJ: to nt»te. in this connexion, that both in (Jower 

 and in I\Mnbrokeshire a band of oolitic limestone att'onls the be.st 

 Inmndary K'twecn K, and K^.-^ 



Along much of the outcrop between the Kbbw and the Taff the 

 miequal resistance to denu<lation of thr limestones forming the 

 Miiddl*' division of the Lower Limestone Shales, and the shales of 

 the u]>per division, is strikingly ex]>resscd in the surface relief. 

 The limestones give rise to a l(»w escarpment-ridgc, sejKirated from 



Newport Memoir. 2nd e<l. p. 19. and New|)ort sheet. 

 • That is. limestones oonsistinjr essentially of erinoid-ossieles and bryoztw, 

 broken and nmnded by roljinfr. reddened with Inematite. and eemented by 

 elear gnmular ealeite. On the character and significance of such limestones, 

 nee E. E. L. Dixon. Gowcr paper, p. 515. 



' ?]. E. L. Dixcm. Gower paper, pp. 197-98, an<l 'The Country around 

 Haverfonlwest ' Mem. <{eol. Surv. 1914. pp. \'.\'t 'M . 



1 o 



