﻿384 THE MIOTIC EOCKS OP MONMOUTHSHIRE. [May 1905. 



which, without indicating an actual unconformity, points to an abrupt change 

 of physical conditions. Taken in connection with the sudden appearance above 

 it of the Ehaetic fauna, it suggests the first complete invasion of the area by the 

 Khgetic sea.' l 



Mr. Strahan also observed that the invasion ' seems to have been 

 sudden.' Probably the phenomena which suggested this view are 

 due to the Rhaetic ocean spreading with comparative rapidity over 

 what were — previous to its ingression — flats of ' Tea-Green Marl.' 

 To the south, around Cardiff, lay a stretch of water, either an 

 extension of the Keuper inland sea which had been reduced by 

 evaporation ; or a lake, which would imply that evaporation had 

 caused a still greater reduction in the volume of water in the 

 Keuper sea, and probably had produced isolated patches of water. 

 In these areas deposition would have proceeded continuously, and 

 therefore in such the most complete sequence from the Keuper to 

 the Rhaetic should be observable. 



The notation adopted in this paper for the various beds is similar 

 to that which I employed when describing the sections in North- 

 West Gloucestershire, Worcestershire, and Sedbury Cliff, but it 

 must be understood that the correlation of the beds seen in the 

 several sections is only approximate. 



The upper surface of the Cotham-Marble equivalent at Goldcliff 

 is conspicuously waterworn, and at the base of the superincumbent 

 shales are pebbles of limestone derived from this bed. There is 

 certainly a non-sequence here ; between the paper-shales and the 

 Cotham-Marble equivalent should come the White Lias. 



For assistance in the field-work my thanks are due to my friend 

 Mr. E. Talbot Paris. 



EXPLANATION OF PLATE XXXII. 



Vertical section at Goldcliff, near Newport (Monmouthshire), 

 on the scale of 4 feet to the inch. 



Discussion. 



Mr. Steahan said that he wished to testify to the value of the work 

 accomplished by the Author, in identifying the various paheonto- 

 logical horizons in the Rhsetic group in localities where that had not 

 yet been fully done. He was unable to agree that there was any 

 overlapping of the 'Tea-Green Marls ' by the Avicula contorta-shales. 

 Those marls varied but little in thickness over the whole region. 

 He had been unable to identify the ' Grey Marls ' of Etheridge, 

 and doubted whether any such subdivision of the ' Tea-Green 

 Marls ' could be made. This, however, in no way impaired the 

 value of the palseontological part of the paper. 



1 Mem. G-eol. Surv. ' The Geology of the South-Wales Coalfield ' pt. i : ' The 

 Country around Newport ' 1899, p. 71. 



