Gilbert. — Geology of Waikato Heads District. 107 



the same place, with those figured by Arber, a selection was made of types 

 that appeared to be new, and forwarded by Mr. Bartrum to Arber for 

 determination, but his death occurred before he was able to examine them. 

 On the banks of the Waikato River near Waimate Creek, at about 

 high-water mark, well-preserved plant-impressions can be obtained from 

 various beds, especially from one of fine white sandstone about 1 ft. in 

 thickness. Some 6 ft. above this bed occurs a bed of coal 12 in. to 18 in. 

 thick associated with a similar fine sandstone. These beds, occurring in 

 the axis of a syncline, are not less than 2,000 ft. above the belemnite- 

 beds, from which they are distant two miles- across the general strike of 

 the sequence, the effect of downthrow along the Maretai fault-plane being 

 taken into account. 



Age of the Older-mass. 



Arber (1917) classes the upper plant-beds at Oruarangi Point in the 

 Neocomian, as did Hochstetter (1867) originally. The fossil plants in 

 the beds mentioned above at Waimate, about two miles up the Waikato 

 River from its mouth, are apparently the same as chose at Oruarangi ; 

 the beds containing them are therefore Neocomian, and hence the lower 

 belemnite-beds are most probably of Jurassic age. 



General History of the Coastal Area South of the Waikato River. 



Mid-Cretaceous uplift and folding of the Jurassic and early Cretaceous 

 sediments (here spoken of as the "older-mass") was followed by dissection 

 and by planation to a greater or less degree ; depression then ensued, and 

 was succeeded by a long period of sedimentation, during which most of the 

 beds of the younger-mass were laid down. Subsequent deformation of the 

 older-mass, involving warping and dislocation of the beds of the younger- 

 mass, and general though unequal uplift, initiated a long period of erosion, 

 during which movements of elevation continued, and the younger-mass 

 was stripped from much of the higher portions of the uplifted area, whilst 

 the older-mass was deeply cut into by superposed consequent streams. 

 At the same time, too, the fault-scarp along the line of the Waikato River, 

 a product of the deformation which followed the conclusion of deposition 

 of the younger-mass, was maturely dissected. 



During the period when the beds of the younger-mass were being laid 

 down slight uplift took place, at least in some localities, as at the Kawa, 

 where the movement was sufficient to bring about sea-planation of certain 

 impure limestones after they had been slightly warped. With slow depres- 

 sion, again, other beds were laid down unconformably above the warped 

 and planed limestones ; local volcanic activity occurred, depositing beds 

 of ash and lava. These were again covered by swamp-silts, and, upon 

 uplift, by wind-blown sands. 



Relation between the Mesozoic Older-mass and the Younger-mass (or Notocene) 



Beds. 



The Notocene beds, using the name suggested by Thomson (1917, 

 p. 408) for the "covering strata" or "younger rock-series" of New Zea- 

 land, were deposited on the eroded surface of the folded older-mass. (See 

 figs. 3, 4, 5, 6, 7, and 8.) 



An outlier of Notocene beds at Pa Brown, high up near the source of 

 the Moewaka Stream, a tributary of the Opuatia, is of great importance 

 as indicating the former greater extent of these beds. This small outlier, 

 covering about a quarter of a square mile, consists of 40 ft. to 50 ft. of 

 platy bands of an extremely hard limestone, containing abundant large 



