460 Transactions. — Geology. 



(a.) At Lake Takapuna (Wairau Creek), about 30 ft. 

 above the outcrop there of the coarse bed, are the black- 

 banded Wairau tuffs. At St. John's College black-banded 

 tuffs, apparently the same, occur some 70 ft. below the fine 

 bed. Neither section is completely exposed, but I could see 

 no sign of a break. 



(b.) At the Manukau Harbour, where the occurrence of 

 these beds does not seem to have been hitherto observed, 

 two outcrops occur, a quarter of a mile apart. One is a 

 coarse bed with fossils, ten species of the Bryozoa being also 

 found at Cheltenham, as well as Pecten burnetti and Bhyn- 

 chonella nigricans. The other is a fine-grained bed, in every 

 way resembling the bed at Parnell, except that its fragments 

 are slightly smaller and its thickness rather less. The 

 coarse-grained bed has larger fragments than at Cheltenham, 

 which is natural enough if the Waitakerei vents were the 

 source ; so that the difference in texture between the two beds 

 is accentuated (Plate XXXYIIL, fig. 1). 



The section cannot be seen in a direct line since two 

 small bays occur at x and y ; but there is no break possible 

 except at one point, the head of the inlet at y, where there 

 has been a fall of debris, so that no section can be seen. 

 This slip may mark a line of fault, but as the beds have the 

 same dip on both sides of it and are similar, and there is no 

 sign of distortion of the strata, there seems no reason to 

 suppose one. The coarse bed is here about 30 ft. thick, the 

 other perhaps 12 ft. 



I wrote that the evidence was cumulative — i.e., the strati- 

 graphy and the palaeontology both point to two beds. In 

 fact, it seems to me improbable that .so many fossils should 

 be preserved invariably in the coarse bed and never in the 

 fine ; that the texture should vary so rapidly ; and that the 

 stratigraphical relations given above, sometimes fairly clear, 

 sometimes obscure, but always indicated, should be always 

 misleading. 



Accepting, then, the conclusion that the beds are two 

 distinct formations of different date, it will be well to con- 

 sider them separately ; and, first, the Cheltenham breccia, 

 because it is the older. 



5. The Cheltenham Breccia. 



The Cheltenham breccia presents usually a bedded ap- 

 pearance, due to the arrangement of fragments of approxi- 

 mately the same size in roughly parallel bands. The 

 coarsest band is usually about a third of the way from 

 the bottom, and the angular fragments scattered through 

 this band are as large as apples. These fragments are im- 

 bedded in a matrix of smaller debris, which forms the rest 



