Thomson. — Geology of Middle Clarence and TJre Valleys. 327 



Range, and it is probable that the hogback is formed of these alone, and 

 that the softer marly limestones succeeding do not form a salient in the 

 relief, so that the total thickness of the whole series may be equal to that 

 of the Chalk Kange. 



Middle Ure Valley. — In the Urc Valley above Waterfall Creek the river 

 runs obliquelv across the strike, and the following rocks were observed 

 in ascending order : (1) Hard mudstones, (2) hard sandstones, (3) gap in 

 succession, (4) thick red decomposed volcanic lava, (5) gaj) in successon, 

 (6) limestojies. much folded and puckered, with dip and strike constantly 

 changing, forming tlie river-banks as far as the Ure Gorge. Fi-om some 

 green bands in the lower end of the gorge I collected sjiecimens of Teredo 

 tubes indistinguishable from those of Teredo heaphyi Zittel. 



From the section in the Blue Mountain Stream which enters the Ure 

 along the red volcanic rock, it a]ipears probable that the above succession 

 is reversed. The lava is in this stream followed (apparently) by white 

 mudstones or marls with poor plant fossils, and these by about 150 ft. of 

 limestone, mostly a white or reddish, fine-grained, rather chalky variety, 

 with oiven bands and much tufaceous material. The limestone is in turn 

 followed by sheared mudstones or muddy sandstones, and may be separated 

 from the latter by a fault. Then follows a further series of similar limestone 

 overlaid bv the Clarentian rocks already described, with ]:)ebbly mudstone 

 near the apparent top. 



If, as I suppose, the succession is here reversed, the volcanic lava follows 

 some part of the Amuri limestone, and quite probably occupies the same 

 position as the tuffs in the Herring River section — i.e.. between the Amuri 

 limestone and Weka Pass stone ; but some earlier volcanic activity must 

 have occurred to account for the tufaceous bands in the Amuri limestone 

 itself. 



Branch, Dart, and. Muzzle Rivers. — -McKay has not made many observa- 

 tions of the Amuri limestone between the Dee and Bluff Rivers, but states 

 that the flint-beds become much thinner south-west of the Dee, have dis- 

 appeared altogether in the Dart, and are not found farther to the south- 

 west. I observed these beds, however, in the Bluff River and Gentle Annie 

 Stream, so that it is improbable that they are totally absent in the inter- 

 vening terrain. McKay states that the Branch Gorge is impassable, but 

 estimates the thickness of the limestones as 1,200 ft. in the Dart Gorge and 

 not much less in the Muzzle, though in the latter it is repeated by faulting. 

 In the Muzzle he states tliat '' there is evidence that the higher beds [i.e., 

 the Cobden limestone and Weka Pass stone] are gradually encroaching on 

 the lower and more characteristic Amuri limestone beds," and mentions 

 finding in the former fragments of a fibrous plicated shell " which probably 

 belong to Inoceramus.'" 



Bluff River. — McKay's two descriptions (1886, pp. 78 and 97) of the 

 Amuri limestone and Weka Pass stone in this section do not tally alto- 

 gether with my observations. The highest bed is. he states, a calcareous 

 sandstone, 15-25 ft. thick, containing various species of Pecten, including 

 P. zitteli, and overlies soft chalk-marls. The lower beds he describes as 

 " a compact fine-grained rock," and he states that '" in its higher beds 

 the harder limestone alternates with soft marl}^ beds, and bands of hard 

 calcareous greensandstone are of frequent occurrence. ... A little to 

 the south-west the Amuri limestone rests on the saurian beds as a gritty, 

 impure limestone." 



