108 Transactions. 



oyster-shells, sharks' teeth, and small indeterminate shell-fragments, under- 

 lain by a thick layer of calcareous sandstone, very similar lithologically 

 to that in the bed of the Opuatia Stream four to five miles farther east. 

 A short distance to the west the Mesozoic rocks of the watershed rise 

 100 ft. to 200 ft. higher. 



An examination of the upper parts of the valleys of the Maretai, the 

 Huruwai, and the Waikawau Streams reveals the same phenomenon as the 

 Opuatia Valley — namely, that the Notocene suddenly appears deep down 

 in troughs in the Mesozoic older-mass. The lowest beds there observable 

 are calcareous sandstone, passing upwards into a hard, scantily fossiliferous, 

 platy limestone, which changes in facies with great rapidity. Again at the 

 Waikato South Head there is a downfaulted block of the Notocene beds 

 which owes its preservation to its resistant character. (See fig. 3.) 



No shore-line deposits have been found in these valleys or depressions 

 to support the view that the Notocene beds were laid down in deeply eroded 

 valleys into which the sea penetrated when the land was depressed, although 

 fragments of Mesozoic rocks were found in a basal bed of the younger-mass 

 near Orairoa Point, half a mile south of the Huruwai Stream. The upper 

 Notocene beds are often of hard, pure limestone, and must have been 

 deposited in deep, clear water at a distance from land. Having in view 

 the fact that the Notocene beds have suffered very considerable erosion, the 

 final conclusion is that they covered the whole area — even the more elevated 

 tracts occupied by the Mesozoic rocks, where now no trace of them is left. 

 They covered a broadly truncated surface of the Mesozoic rocks, and when 

 later uplift set in would be removed most readily from the uplifted areas. 

 As pointed out, the Notocene beds in several places occupy valley-like 

 depressions in the Mesozoic strata, either as the result of faulting or owing 

 to involvement in the folding of the Mesozoic older-mass that occurred 

 subsequent to the deposition of these younger-mass beds. The latter 

 supposition appears the more probable explanation, although a more careful 

 examination of the district is needed to settle the point. 



The Younger -mass (or Notocene) Beds. 



The beds of the younger-mass dip slightly to the south along the coast, 

 and their sequence from their lowest upwards is not easy to determine. 

 The following is the probable upward sequence :- — 



(1.) At the base algal tabular limestone. It contains angular fragments 

 of the underlying Mesozoic rocks where it rests on the latter at 

 Orairoa Point, north of Huruwai Stream. This limestone seems 

 to rest on still lower blue sea-muds, and to lose both its tabular 

 and brecciaceous character. 



(2.) Grey calcareous sandstone, 300 ft. thick in places such as the 

 Opuatia Stream valley and the upper Waikawau, changing to a 

 blue sea-mud at the base of the outcrops on the coast between 

 the Waikawau and Kawa Streams. 



(3.) Tabular limestones. At the Waikawau and the Ruahine Streams, 

 and along the northern half of Waiwiri Beach, the upward suc- 

 cession is of alternating calcareous sandy beds, and thin, hard, 

 marly limestone, all becoming tabular, sandy, or even shelly 

 limestones farther back from the coast and south from the 

 Ruahine Stream. They appear as a pure, hard, coarsely crystal- 

 line limestone in a large cave two miles from the coast on the 

 north bank of the Waikawau Stream. Half-way up this series 

 of thin beds a discontinuity occurs in the Waikawau section. 



