Button. — Geology of North-eastern Otago. 425 



here it is quite evident that the gravels have shpped with the 

 silt, and that both retain their relative positions. North of 

 Oamaru many road sections show the silt to be distinctly inter- 

 stratified with gravel beds, but I observed no fossils in them. 



Hampden District. 



Sedimentary Rocks. — Onekakara Bay lies between the Penin- 

 sula of Moeraki and Lookout Bluff, just south of the mouth of 

 the Otepopo Kiver. Hampden is a little to the south of the 

 centre of the bay (Section VI.). The sedimentary rocks consist 

 of blue clay (Onekakara clay), overlain by a soft dark volcanic 

 sandstone, or rock-saud, which weathers greenish ; the whole 

 being covered by beds of gravel and silt. The sandstone is 

 found chiefly north of Hampden, but it also occurs at Moeraki, 

 It is in the blue clay, south of Hampden, that the Moeraki 

 septaria are found. 



The sandstone consists largely of well-rounded volcanic 

 debris, and is black on first breaking, but soon turns greenish. 

 A similar soft sandstone is largely developed in the banks of the 

 Otepopo River, near the railway ; it differs in being almost 

 entirely a volcanic sand, and in weathering to a distinct green 

 colour. The sandstone here is also underlain by blue sandy 

 clay, with dark soft sandstone again below it. It is this latter 

 sandstone which occurs at the Herbert tunnel. Small beds of 

 lignite are associated with it, which were explored by Mr. Fen- 

 wick in 1875. 



As I have already mentioned, the age of these beds is a 

 matter of difference of opinion. In 1884, Mr. McKay divided 

 them into three divisions, all of which he considered to belong 

 to the cretaceo-tertiary or Waipara System. The stratigraphi- 

 cal evidence he produces in favour of this view is the mistaken 

 idea that they are overlain by the tuffs below the Ototara lime- 

 stone in the Waireka Valley ; this relation depending entirely 

 on the supposed equivalence of the volcanic rocks of Mount 

 Charles and of Kakanui. Of palseontological evidence, Mr. 

 McKay adduces none, for he gives no list of fossils ; but to get 

 rid of the evidence in favour of their miocene age, he makes two 

 most extraordinary statements : — 



(1.) Previous collectors have " imperfectly collected at 

 points where slips have mixed them [fossils] with 

 the recent shells of the coast-line." 



(2.) Previous paleontologists have examined a mixture of 

 cretaceo-tertiary and recent shells, " hence possibly 

 one reason why these beds have been by some pre- 

 vious observers referred to the miocene period."* 



• " Rep. Geoh Expl.," 1883-84, p. 62. 



