Gilbert. — Geology of Waikato Heads District. 



103 



heading 30° to the north and striking 30° north of east, roughly along the 

 line of the river, and traceable for some 50 yards. The limestones on the 

 north must be downthrown 200 ft. to 300 ft. at least. This fault may very 

 well be one of the step-faults of the zone of faulting referred to above. 

 Brown sands and sandy limestone are here brought in contact with Mesozoic 

 shales (belemnite-beds) dipping 45° south west and striking 30° west of north, 

 forming the southern (or upthrow) side of the fault. The shales are finely 

 comminuted in a band some 20 ft. wide along the line of the fault. 



The most important reason for suggesting faulting is the abrupt 

 termination of the older rocks along a fairly definite line, and their 

 replacement by an area of much later sedimentation. Along the maturely 

 dissected scarp of the Waikato fault between Maretai Stream and the South 

 Head, wave-attack has in places produced typical sea-cliffs, above which are 

 hanging valleys. 



It is possible, though unlikely from their position, that river-planation, 

 and not wave-attack, was responsible for the wearing-back of these cliffs. 



The Area South of the Waikato. 

 General Description. 



The country to the south of the Waikato Eiver dealt with herein is an 

 upland, 600 ft. to 1,200 ft. above the level of the sea, consisting of uniformly 

 resistant rocks, except along the sea-coast, where the upper portions are much 

 less resistant than the lower. This upland is deeply dissected by stream- 

 valleys running north-west and east from the main watershed, which sends 

 out numerous sharp spurs, so that the surface is very uneven and rugged, 



Fig. 4. — Section along line AB of map. 



Fig. 5. — Section along line CD of map. 



Fig. 6. — Section along line EF of map. 



presenting few level tracts. The rocks consist of a basement (herein called 

 the " older-mass ") of symmetrically folded sediments, on the eroded and 

 weathered surface of which in many places the younger-mass beds* rest 

 horizontally, and therefore unconformably ; these latter consist of mode- 

 rately resistant marine sediment. They again are covered unconformably 

 along the coast by less resistant Pleistocene and Eecentf clays and sands. 



* Part of the Notocene of Thomson (1917, p. 408). 

 f The Notopleistocene of Thomson (1917, p. 411). 



