Vol. 67.] THE CARBONIFEROUS SUCCESSION IN GOAVER. 



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ported a rich calcareous fauna 

 belonging to standard groups, 

 chiefly crinoids and brachiopods ; 

 the remains are found in both the 

 shales and the subordinate lime- 

 stones. In Gower, as in the 

 South- Western Province generally, 

 the conditions, for some reason, 

 were unfavourable to tho forma- 

 tion of chert and dolomite. The 

 thick limestone in the middle of 

 the zone, which is widespread, 

 consists partly of oolite, and may, 

 therefore, have resulted from a 

 temporary shallowing (fig. 8). 



(iv) The change from K 

 to Z. — Probably in Gower, and 

 certainly over the western part of 

 the South- Western Province, this 

 change of fauna Avas accompanied 

 by a rapid and long-enduring 

 lithological change, from a domi- 

 nantly argillaceous to adominantly 

 calcareous facies of sedimenta- 

 tion : for there the junction of the 

 zones is the junction of the Lower 

 Limestone Shales with the main 

 limestone-mass of the Carboni- 

 ferous Limestone Series. This 

 widespread change in fauna and 

 rock-type probably resulted from 

 some important physiographic 

 event elsewhere, but apparently 

 it was not accompanied in Gower 

 by change of depth, for the Z 

 limestones closely resemble the 

 thin limestones in K. It is note- 

 worthy that ' contemporaneous ' 

 dolomitization and the formation 

 of chert practically came in at 

 the period of the change ; chert 

 is especially frequent near, but 

 not below, the junction. 



(v) Conditions during the 

 two sequences : (1) Z, C l and 

 the Modiola phase at the 

 base of C 2 ; and (2) C 2 & S. 

 — A close parallel may be drawn 

 between these two sequences, es- 

 pecially in South- Western Gower 

 where the lithological series is 



