THE GREAT MARLBOROUGH CONGLOMERATE 359 



The continuity of the conglomerate in the Middle Clarence 

 Valley throughout a line of outcrop thirty miles in length indicates 

 that it was there deposited as a piedmont alluvial plain and not as 

 isolated fans. A somewhat similar feature now in course of 

 formation by several rivers, between the Seaward Kaikoura Moun- 

 tains and the sea, in the vicinity of Kaikoura, constitutes the 

 Kaikoura Plain/ 



It may be noted that both Hector"" and McKay^ expressed their 

 conviction that the conglomerate was of fluviatile origin, but both 

 regarded it as the work of a single river system. 



HYPOTHESIS TO ACCOUNT FOR THE PECULIAR FEATURES OF THE 



CONGLOMERATE 



From the description in the preceding pages it is apparent that 

 the Great Marlborough Conglomerate, in the Middle Clarence 

 Valley, rests conformably on the Grey Marl, and yet is largely 

 made up of material derived from that series and the beds con- 

 formably underlying it. Much of the material, moreover, agrees 

 exactly in facies with the beds upon which it rests, and undoubtedly 

 has been transported only a comparatively short distance. 



In order to account for the supply of this material it is neces- 

 sary to assume that a neighboring area was differentially elevated 

 to the extent of perhaps as much as twelve thousand feet (the 

 maximum thickness of the Amuri and Grey Marl series, as exposed 

 in the neighboring Coverham section being estimated by McKay"* 

 at that amount), without seriously disturbing the horizontal atti- 

 tude of that portion of the Amuri^ and Grey Marl series, which, a 

 little later, had the conglomerate deposited upon it, and which, 

 as shown in Fig. 2, is, in part, still preserved. 



Of the exact nature of this uplift no information is to be obtained, 

 at least in the present state of our knowledge, from the pre- 

 Cretaceous rocks in the vicinity, for their structure is obscure, nor 



'See McKay, op. cit. {1886), p. 126. 

 = Sir James Hector, op. cit. {18S6), p. xxxvi. 

 3 A. McKay, op. cit. (18(12), pp. 4-5. 

 1 A. McKay, op. cit. {1886), p. 90. 



5 The Amuri Series as here understood includes the whole of the "Lower Green- 

 sand" and " Cretaceo-Tertiary " of Hector's Survey. 



