530 ME. E. E. L. DIXON AND DR. A. VAUGHAN ON [NOV. I9H, 



radiolarian cherts in Carmarthenshire immediately and conform- 

 ably, rests Unconformably upon S 2 ; at Ifton cavities (channels 

 and swallet-like passages) penetrating the limestone to a depth 

 of at least 40 feet below its uneven upper surface have been 

 filled with an original deposit of Millstone Grit. The un- 

 disturbed character of the Grit in the cavities shows that, here as 

 at the Haverfordwest occurrence described by Prof. 0. T. Jones, 

 the limestone was raised above sea-level and ' piped ' by subaerial 

 erosion prior to the deposition of the Grit. No direct evidence as to 

 the exact period of the elevation is available ; but the fact that the 

 change from D.,_ 3 to P has been marked by a considerable physio- 

 graphic change in the South-Western Province (p. 524) suggests 

 that the movement took place at the close of D. 1 The relationship 

 of the uplift to the hiatus between S 2 and the Millstone Grit would 

 then be analogous to the relationship of the uplift at the end of C x 

 to the hiatus between Z and S a at Pendine (fig. 7, p. 527). Outside 

 the South- Western Province, evidence of emersion between D and 

 P has been found in places by Dr. Sibly and Mr. C. B. Wedd, 

 although, as a rule, there is no such break at this horizon. 2 



It appears, therefore, that the radiolarian cherts of the South- 

 western Province have been the first deposits formed after a 

 movement of elevation which has left indubitable traces in that area. 

 Consequently, tested in this way their suggested relationship to 

 Modiola phases receives support. 



(7) Lagoon-Phases outside the South- Western, Province. 



In conclusion, it may be mentioned that the conditions under 

 which the lagoon-phases of Gower have been deposited have been 

 paralleled elsewhere and at many other horizons. Where, in such 

 cases, the sediments have a calcareous, or a calcareous and argil- 

 laceous, facies, as, for example, the Burdiehouse-Limestone Group 

 of Scotland, the Upper Bhaetic and Cotham-Marble Group, 3 and the 

 Solenhofen Slate, their origination in shallow areas or even lagoons 

 has been generally recognized, despite the fine grain of some of their 

 most characteristic rocks. It is of interest, therefore, that several 

 resemble the phases of Gower, not only in this fine grain and, 

 frequently, in a fine lamination, but also in their relation to earth- 

 movements. 



As regards the radiolarian phase at the base of P, though it is 

 not suggested that all radiolarian deposits have had a similar 

 origin, it is certain that some, at least, of those which appear, from 

 various considerations, to have been deposited in shallow water 



1 It is not, however, suggested that the movement resulted in unconfomity 

 everywhere, for in Carmarthenshire the sequence both below and above the 

 radiolarian cherts is unbroken ; see T. 0. Cantrill, ' The Country around 

 Ammanford ' Mem. Geol. Surv. 1907, pp. 72-76. 



2 Q. J. G. S. vol. lxiv (1908) pp. 63 & 81. 



3 The Lower Bhaetic appears to be less peculiar in its rock-types than the 

 "Upper. 



