330 Transactions. 



of the river, lower down, it is seen to consist of various types of calcareous 

 sandstone and argillaceous limestone, weathering to light-brown cliffs, and 

 is separated into two parts by a thick band of mudstones very similar to 

 the " grey marls."' The strike at the middle of the bend round to the 

 Clarence Eiver is N. 15° E., dip 45° to the west. At the junction with 

 the Clarence the strike is N. 50° E., and the dip 60° to the north-west. The 

 limestone continues down the Clarence River for about 300 yards, and is 

 here an argillaceous limestone with numerous partings, some of which con- 

 tain dicotyledonous leaf impressions. Marine fossils occur sparingly, and 

 are chiefly Oamaruian moUusca. 



Age and Origin of the Amuri Limestone. — The only fossils found in the 

 Amuri limestone of the Middle Clarence Valley are the Teredo tubes in 

 chalky limestone from the Bluff River and from the Ure Gorge, and the 

 indeterminable brachiopods found in the glauconitic partings in the flint- 

 beds of the Bluff River. The Teredo tubes are indistinguishable from 

 those of the Oamaruian Teredo heapJigi Hutton, but it is doubtful whether 

 these deserve specific recognition, and fossils of such a nature are certainly 

 insufficient for purposes of correlation. Probably by renewed collecting 

 determinable brachiopods may be obtained froni the Bluff River flint-beds 

 which will suffice to fix the age of these beds. Meanwhile, in the lack 

 of direct palaeontological evidence, the determination of the age of the 

 limestones must remain a matter of inference. A lower limit of age is 

 fixed by the underlying fossiliferous Clarentian mudstones of Sawpit Gully, 

 which contain middle Cretaceous fossils up to within a few feet of their 

 junction with the flint-beds. An upper limit is fixed by the overlying 

 phosphatic greensandstones and Weka Pass stone of the Herring River, 

 both of which contain Oamaruian fossils of at oldest Oligocene age, and, 

 in other areas where these horizons are unfossiliferous, bv the still hisher 

 "grey marls," which are Oamaruian. 



Woods (1917, p. 2) has argued from the facts that the Amuri lime- 

 stone in North Canterbury and East Marlborough is always overlain by 

 Oamaruian (Miocene) rocks, and is underlain in the former area by Piri- 

 pauan (Senonian) beds but in the latter area by Clarentian (Albian) 

 beds, that the limestone must be unconformable both to the Piripauan 

 and Clarentian. and that it is probably Eocene. 



In 1916, before I had visited the Herring River and Bluft' River sec- 

 tions, I discussed the lithology, thickness, distribution, and stratigraphical 

 relations of the Amuri limestone, including the flint-beds, and suggested 

 that it was in large part a chemical deposit. I stated mv belief that it 

 was everywhere conformable to the underlying rocks, ranging in age from 

 Piripauan to Oamaruian in North Canterbury, and from Clarentian to 

 Oamaruian in the Middle Clarence area, and that the flint-beds represented 

 a definite horizon absent from the southern area. The discovery by 

 Speight and myself of fossils in an interbedded tuft' near the top of the 

 limestone of the Trelissick Basin proved the Lower Oamaruian age of the 

 top of the limestone in this locality. A corollary of the conformity with 

 the underlying beds, by which the conclusion may be tested, is that the 

 underlying rocks of the intermediate district — viz., the Puhipuhi Moun- 

 tains — where the limestone is intermediate in thickness, must at the top be 

 intermediate in age between Piripauan and Clarentian. Unfortunatelv, a 

 spell of bad weather prevented my attempted examination of the Puhipuhi 

 Mountains in 1916, and no further opportunity of exploring this area has 

 presented itself. Meanwhile the discovery of the probable unconformity 



