THE GREAT MARLBOROUGH CONGLOMERATE 355 



Ure valley showed that the great majority, at least, of the bowlders 

 of igneous rock in the bed of that river were brought in by tributaries 

 from the northeastern end of the Kaikoura Range where they are 

 present in place. McKay states definitely that these rocks are 

 present throughout a great part of the length of the outcrop in the 

 Middle Clarence Valley^ and notes their absence only at the south- 

 west end of the strip.^ 



The writer, however, has been forced to conclude, from the 

 results of his own examinations, in which Dr. J. A. Thomson kindly 

 assisted, that igneous rocks of the Tapuaenuku type are absent 

 from the conglomerate at all the points in the Clarence Valley at 

 which it was examined. No such statement can, of course, be 

 made with reference to the conglomerate at the source of the Ure. 



The absence of these rocks from the conglomerate in the Dee 

 gorge is especially significant since the intrusions are now exposed 

 in the immediate vicinity and supply the bulk of the bowlders in the 

 bed of the Dee. 



The constituents of the conglomerate in the Dee and Mead 

 gorges, as noted by the writer, are as follows: 



In the gorge of the Dee. — Small well-rolled pebbles of pre- 

 Cretaceous or "Maitai" rocks, both graywacke and jasperoid, are 

 very abundant. Much rarer are lumps of Amuri Limestone of 

 irregular, angular shape, up to the size of a man's head, and there 

 are some pieces of flint, apparently derived from the flint beds which 

 replace the basal part of the Amuri Limestone; Still more rare 

 are lumps of very fossiliferous Tertiary sandstone, and of Cre- 

 taceous sandstone containing fragments of Inoceramus; these 

 range up to i ft. in diameter. The largest blocks, generally several 

 feet in diameter, are of crumbling, sandy marl or mudstone exactly 

 agreeing, lithologically, with the upper beds of the Grey Marl 

 present in place immediately below the conglomerate. All the 

 larger blocks are arranged with their largest flat surfaces parallel 

 to the stratification. There are present also some spherical con- 

 cretions, I ft. to 2 ft. in diameter, resembling those in the Grey 

 Marl. Igneous rocks are represented by bowlders of coarse-grained 



^ A. McKay, op. cit. {iSgz), p. 4. 

 ^Ibid. {18S6), p. 121. 



