326 Transacfions. 



that McKay described the Weka Pass stone in the Mead and Dee Gorges 

 also as a calcareous sandstone, but it is certainly more argillaceous than 

 arenaceous in these localities. 



I observed the base of the flint-beds in Sawpit Gully. The junction 

 with the Clarentian appears to be perfectly conformable, though quite 

 sharp. The lowest flint-beds are dark throughout, and contain no dolo- 

 mitic exteriors. The up])ermost Clarentian beds contain mucli pyrite in 

 nodules, and show a yellow efflorescence. Microscopic examination of the 

 lowest flint-beds suggest that they are replacing rocks in part clastic. 



Isolaled Hill Creek.— In the Ure Gorge the sequence of the various beds 

 of the Amuri limestone is difficult to interpret, owing to the complex folding 

 and faulting that has taken place. Tlio flint-beds at the base are, however, 

 well exposed in the Isolated Hill f'reek, which has cut a gorge through 

 them (Plates XXVII, XXVIII). They appear to be much thinner than in 

 the Chalk Eange, and not much more than 500 ft. in thickness. The junction 

 with the underlving Clarentian rocks is well exposed, and is not only con- 

 formable, but appears to show a transition between the two groups of 

 rocks. Near the base black flints in hand-size nodules and lenticules lie 

 in a coarsely crvstalline dolomitic matrix, and the flints themselves contain 

 many crvstals of dolomite. Followed downwards, the flints contain fewer 

 and fewer crystals, and at the same time become less pure and lighter 

 in colour till they can hardly be distinguished from hardened mudstone, 

 while the matrix also alters gradually into a grey micaceous mudstone. 

 The above transition takes place within 2 ft. of rock. Forty feet below 

 this transition there is a thin layer of im]uire flints and dolomite, the 

 crvstals of dolomite being relatively large. In the intermediate 40 ft. of 

 mudstone there are large concretionary masses, 3 ft. in length and 18 in. 

 across the bedding, consisting of lenticules of black flint in a crystalline 

 dolomitic matrix. 



It might be argued that the flint is secondary and has invaded the 

 uppermost beds of the Clarentian. obscuring the true junction. But even 

 if the flint-dolomite is secondary it is replacing calcareous rocks, and the 

 transition in this case is from Clarentian mudstone to limestone by the 

 intermediarv of calcareous concretions, and I see no escape from the 

 conclusion that the Amuri limestone is here conformable to the Clarentian. 



Upper Ure V((lle>/. — In the upper inverted limb of the overturned 

 syncline behind the Chalk Range the Amuri limestone forms a hogback 

 ridge, cut through on the northern side of the Ure River from Limestone 

 Hill to the White Bluffs by several goi'ges. From the smaller width and 

 height of this hogback riclge it appears at first sight that the limestone 

 is here considerably thinner than in the Chalk Range, on the lower limb 

 of the synclinal, t observed the basal beds, here lying uppermost, in the 

 large tributarv from the Blue Mountain, but could not penetrate down 

 the gorge to observe the upper beds. The beds are here striking in a 

 north-east direction, and dipping at angles of 40° to 60° to the north-west. 

 The sequence wiH be described as if the beds were not overturned. The 

 Clarentian mudstones are followed perfectly conformably by thin lenticular 

 flint-beds with mudstone intercalations, passing u]) into greener fiints with 

 dolomite crystals, the whole being some hundreds of feet thick. These 

 are followed by hard chalky limestone with reddish-brown blobs of flint, 

 also several hundr(>d feet thick, and these again by limestone with black 

 flint lenticules. beyond which the section could not be followed. The total 

 flint-beds do not seem nuich inferior in thickness to those of the Chalk 



