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Transactions. 



Manukau Harbour that penetrates to Otakuhu — indeed, in most of the 

 harbour's ramifications — similar evidence is available. These silts are now 

 being cut back rapidly by wave-action at high-water,* and present low cliffs 

 that rise to no great height above high-water level. 



V^"Watte ?n g-ta>.3eo6s 1-yV 



r^b^^^rbrfcL^VL. 



Fig. 2. — A. Manukau Harbour. B. Waitemata Harbour (Grafton Gully continuation). 



The story they unfold is briefly as follows : After their deposition, uplift 

 over the whole Auckland area occurred, of which local evidence is found 

 also in the Waitemata Harbour. | Following the uplift the silts were dissected 

 by the various streams emptying into the Manukau Harbour, such as the 

 Waiuku, and the present channels thus formed. Depression soon followed, 

 admitting the tidal waters into the stream-courses. (See fig. 2, A.) 



Mutual Relations of the Areas North and South of the Waikato River : an 



Hypothesis of Major Faulting. 



It is believed that the northern shore of the Manukau is roughly coincident 

 with a fault-line running east and west, and that the Waikato River in the 

 last few miles of its course traverses another fault-line parallel with the 

 first, cutting the Mesozoic rocks at right angles to their strike. This latter 

 has been called the Waikato fault. The country between is deemed faulted 

 down at least 2,000 ft., leaving the eroded Mesozoic rocks on the south 

 standing 12,000 ft. above sea-level. 



Fig. 3. — Coast section, Waikato South Head, a', belemnite marly shales ; a, sands 

 and shales ; b, sandy limestone ; c, brown sands and silts ; d, gray clays 

 and silts ; e, red clays and sands ; /, zone of comminuted shale ; g, fault. 



Though no conclusive evidence of the faulting could be obtained, the 

 south bank of the Waikato River presents the appearance of a deeply dissected 

 fault-scarp ; and, further, at the South Head there is a nearly vertical fault, 



* Tidal interval at spring tides, 14 ft. 



f I am indebted to Mr. J. A. Bartrum for pointing this out to me, and for a 

 sketch of the continuation of Grafton Gully into the harbour, which he drew from 

 data supplied by the Harbour Board, and which is reproduced in fig. 2. B. 



