1919.] Wild and Speight.—Limestones of Canterbury. 
181 
almost the only places where they occur being the Ivakahu Gorge, where 
they are associated with phyllites, and on the Malvern Hills, where they 
occur in connection with basic ash-beds and lava-flows. In neither of 
these cases is the deposit of sufficient extent to warrant serious consideration 
as a source of phosphate. 
In two areas, one at the north and another at the southern end of the 
provincial district, limestones of Tertiary age exist over wide tracts of 
country, and, as both these areas are served by main and branch lines of 
railway, most consideration must naturally be given to them. Between 
these localities, at the base of the eastern foothills of the Southern Alps— 
e.g., at Oxford and Mount Somers—and also in the interior mountain 
basins— e.g., at Castle Hill, in the basin of the Esk River, at Redcliff Gully 
in the Rakaia Valley, and in the Rangitata Valley—isolated deposits occur, 
some being too remote from settlement and good communication to be 
seriously considered as sources of limestone or phosphate, unless the latter 
be in exceedingly rich deposits—a condition which, unfortunately, does not 
occur. It will be best to take the two chief districts first and consider 
the circumstances of the smaller areas later. 
North Canterbury. 
The area over which limestones occur in North Canterbury extends 
from the neighbourhood of Mount Grey to north of Kaikoura, where it 
junctions with the limestones of the Clarence Valley, which are, however, 
beyond the scope of this report. The deposit is not continuous over the 
area, since its continuity is broken by ridges and islands of older, non- 
calcareous greywackes and slaty shales, which project through the covering ; 
but there is reason to believe that the different apparently isolated areas 
were once much more closely connected, and that a fairly complete veneer 
of Tertiary limestones once covered the country. Further, later deposits 
of Tertiary age have covered up the limestones, so that the exposures 
are now usually in the form of long strips and are rarely to be seen over 
broad surface areas. The beds have been folded to a moderate extent, 
or have been tilted as the result of fault movements so that they frequently 
present bold escarpments where their geological relations can be most 
readily studied. 
The chief areas where the deposits occur are as follows :— 
(1.) From Mount Grey to the Middle Waipara, and on through Weka 
Pass to Waikari and Scar gill. This area was once continuous 
over a wide extent of country. It has, however, suffered seriously 
from erosion, and remnants of the covering sheet are now found 
as semi-detatched masses at Heathstock, Mount Mason, and 
in the Culverden basin, notably in the last-mentioned area in 
the valleys of the Pahau and Mason Rivers. Detached outliers 
also occur in the valley of the Mandamus and near Hanmer 
Plains. 
(2.) From the Lower Waipara Gorge, along the flanks and crest of the 
Limestone (or Cass) Range, parallel with the coast to Motunau 
River. 
(3.) From Stonyhurst across the mouth of the Blyth and Hurunui 
Rivers to Port Robinson and the immediate vicinity of the 
Cheviot township. 
