104 The N.Z. Journal of Science and Technology. [April 
beds are penetrated by two well-defined basaltic sills, which have altered 
the coal-beds, top and bottom, into an impure anthracite exhibiting a 
well-defined columnar structure (fig. 6). The prisms are up to 1 ft. in 
length, and about 2 in. in diameter. At this point the beds have a dip 
to the south-east, but on following them to the south across the terrace 
and undulating country which lies in the angle of the river and Iron 
Creek the direction of the strike gradually changes till it is north and south, 
with a dip to the east of 40°. The beds consist of sands with concretionary 
layers, one such layer containing numerous specimens of Conchothyra 
'parasitica McCoy, which fixes the age of the beds as definitely Cretaceous, 
and as equivalent to the coal-measures of Malvern Hills and the lowest 
beds of the Trelissick Basin and Waipara. 
On the west side of Iron Creek there is a special development of white 
sandy beds which pass up into greensands, all dipping east. On the east 
side the beds are repeated with a dip to the west, but good exposures are 
rare. This synclinal arrangement is characteristic of the beds in Iron 
Creek (see fig. 7). 
In the first branch coming in on the eastern side of Iron Creek the lower 
portion of the series is exposed. Here are sands and sandy clays and shales 
with a bed of impure coal 2 ft. thick, striking north and south and dipping 
west at an angle of 80°. This lies close down on the greywacke, as in 
Winding Creek. Above them are sands, whitish and yellowish-white in 
colour, becoming glauconitic in the higher levels, these latter being light 
green and dark green alternately, and continuing into the bed of the 
creek, where they become a true greensand and have a dip of 85° to the 
west. On a high bluff in the bush on the east side of the creek these beds 
are again exposed, with the same dip and strike noted above. 
Farther up the main creek similar beds are exposed, lying on the 
greywacke and bent up into an acute syncline. The lower beds are 
sometimes distinctly glauconitic, with occasional yellow efflorescence ; the 
oxidation of the iron present in the glauconite produces everywhere in the 
bed of the creek a distinct deposit of oxide of iron, colouring the stones 
and the water occasionally and thus accounting for the name by which 
it is known. 
On the east side of the creek, lower down, in a place partially covered 
with a shingle-slip, is an apparent overthrust fault, the greywacke lying, 
as far as can be seen, over the coal-measures. The latter consist of white 
:sands and impure- coal, dipping south-east 70°. The disturbance may be 
sympathetic with the folding which the beds have been subject to along 
the line of Iron Creek, a disturbance which seems more pronounced on the 
east and therefore likely to be associated with overthrusting, or it may 
be merely the effect of surface creep. As the section is somewhat obscure 
the disposition of the beds cannot be made out for certain, but the first 
hypothesis appears to me to be the more probable, and is supported by 
the occurrence in Bushy Creek referred to previously. 
Just below this point a large dyke, 12 ft. to 15 ft. in width, cuts across 
the creek, striking west-south-west and east-north-east, and dipping 
towards the south at an angle of 70°. The beds alongside it are changed 
in colour from green to red as a result of oxidation associated with the 
heating effect at the time of intrusion. Close alongside the dyke the 
greensands are bent up into a closed syncline. 
( To be continued.) 
