NORTH CAPE DISTRICT
The North Cape district lies in the extreme north-east of the North Auckland Peninsula. It may be described as an elevated rocky area of about 5 sq. miles which was originally an island but is now attached to the mainland by an extensive area of low-lying sand country called Waikuku Flats. On its eastern coast is a small island, Murimotu, which can be approached by land at low tide. The eastern tip of this island is called North Cape, site of a navigation light.
When viewed from the south the surface of the North Cape district is seen to be a dissected plateau of the order of 500–600 ft above sea level. Kerr Point, the highest part of this tableland, is 769 ft. It has been uplifted relative to Waikuku Flats by faulting. The coastline is in a comparatively youthful stage of development, for it consists of rugged sea cliffs up to 500 ft high. At the foot of the cliffs is a broad, flat, horizontal platform, whose formation is perhaps due to storm waves. The rocks consist of spilites (lavas that are submarine in origin and have a distinctive ellipsoidal shape) into which have been intruded a series of ultra-basic rocks (gabbros and peridotites) which have been later altered to serpentinites. Still later in geological history there was deposited a series of impure limestone, conglomerate, and sandstone on the west of the North Cape block. The surface of the plateau is littered with boulders, fragments, and dust of high-grade (69 per cent ferric oxide) limonite (iron ore), which has been formed by the weathering of the ultra-basic rocks. It has a poor soil and supports a stunted scrub vegetation.
The low country to the south-west of the North Cape district, called Waikuku Flats, is covered by alluvium and swamp material and is margined by sand dunes. Scrub and wiwi are the dominant vegetation. Among the sand dunes on the western shore are many shells of the terrestrial gastropod Placostylus hongii ambagiosus. In the bush remnant around Uniwhao Trig. Station at 2,113 ft above sea level to the south-east of Hooper Point the Placostylus can be found alive. The dunes also abound in ancient Maori middens, wherein are human bones and obsidian flakes with occasional polished stone adzes.
The serpentine deposits at North Cape have recently been exploited, the rock being mixed with superphosphate to give a fertiliser called serpentine superphosphate. A clay road has been constructed along the plateau from the Spirits Bay – Te Hapua Road. At a distance of about 10 miles the road forks, one branch going north to the quarry and the other south to a loading ramp on the north side of Parengarenga Harbour just inside the heads. The rock is loaded on to barges which are towed to Auckland by ocean-going tugs.
by Robert Findlay Hay, M.A., B.E.(MINING), Scientific Officer, New Zealand Geological Survey, Otahuhu.