362 C. A. COTTON 



the supply of coarser waste. It is probable that the old land had 

 previously been reduced to senile relief. SHght regional uphft 

 would account for some contemporaneous erosion of the Grey 

 Marl/ as it would bring the landward margin of the deposits into 

 the zone of erosion, but it is possible that this is to be explained by 

 sKght differential uphft heralding the somewhat later uphft that 

 supplied the material of the Great Marlborough Conglomerate. 

 At this stage the maximum thickness of the accumulations in the 

 geosynchne had reached about twelve thousand feet.^ 



According to the writer's hypothesis, a normal fault was next 

 initiated approximately along or parallel to the line of the great 

 reversed fault previously referred to (see Fig. 2), that was formed 

 during a later period of folding, and now bounds the Clarence 

 Valley on the northwest side, separating the conglomerate from the 

 pre-Cretaceous rocks of the Kaikoura Range. The earlier normal 

 fault, being a line of weakness, may have determined the position 

 of the later reversed fault. 



Uplift of the block northwest of the fault plane took place, 

 initiating a period of active denudation along the fault scarp. 

 Some portion of the old land appears to have participated in the 

 uplift, and its revived streams no doubt kept up the supply of 

 well-rolled "Maitai" pebbles which are common in the con- 

 glomerate. Some of these, however, may be a rewash of the basal 

 conglomerate of the Amuri Series.^ The streams from the old 

 land, in their lower courses, crossed the uplifted younger rocks, 

 and, as they emerged from young gorges in the fault scarp, built 



' Thomson, op. clt. ^ McKay, op. cit. 



3 Since the above was written the writer has had an opportunity of reading a paper 

 by A. C. Lawson entitled "The Petrographic Designation of Alluvial Fan Forma- 

 tions" {Bull. Dep. Geol., Univ. Cal., VII, No. 15, 1913), in which the nzxae fanglomerate 

 is proposed for the class of deposit to which the Great Marlborough Conglomerate 

 belongs. Lawson regards all rounded pebbles in fanglomerate as derived from older 

 conglomerates, and, if it were possible in this case to regard them all as a rewash, 

 both the amount of uplift and the area of the uplifted block that it is necessary to 

 assume would be considerably less than on the hypothesis that they are derived from 

 pre-Cretaceous rocks in place. The writer is not, however, prepared to admit that 

 all the small well-rounded material is so derived, although a possible source of supply 

 is the Cretaceous conglomerate (McKay, op. cit. [1886], p. 90), which locally, at 



