1918.] The N.Z. Journal of Science and Technology. 109 
through a slope deposit in which a large proportion of the fragments is 
hornfels, and the gravels of Eight-mile Creek indicate that part of its course 
is through greywacke and argillite. 
The granite that intrudes the rocks of the Aorere series outcrops along 
the Buller for ten miles eastward from Eight-mile Creek. It is part of 
the great granite batholith that southward forms Victoria Range and north¬ 
ward Mount Newton (4,M3 ft.). To the eastward of the area mapped* 
occurs another mass of granite, from which Mount Murchison (4,534 ft.) 
has been carved. 
Tertiary rocks cover a large area, and in the lower valley of the Maruia 
are seen to rest on the denuded surface of the granite. The lowest beds 
are arkosic grits, which, in places, grade into thin inconsistent bands of 
quartz conglomerate and at many points are current-bedded. These rocks 
are overlain conformably by mudstones darkened with carbonaceous matter 
and containing occasional sandy layers. These in turn are covered by a 
second set of quartzose beds which in upward sequence become finer and 
calcareous, grading into an argillaceous limestone. The beds in the locality 
just described have gentle dips, and form a syncline with the axis striking 
marly east and west. The limestone occurs only in the centre of the fold 
and forms a tableland bordered on all sides by vertical cliffs. The northern 
end of this plateau overlooks the Four-river Plain, and is known as the 
Sphinx Rock. The gently dipping beds extend southward for many 
miles, forming the ridge of hills between the valleys of the Maruia and 
Matakitaki Rivers, and terminating high on the northern spurs of Mount 
Mantell. 
To the westward of the area above described a narrow belt of steeply 
dipping limestone and argillaceous sandstone crosses the Buller at the horse¬ 
shoe bend one and a half miles above Newton Flat. This zone of Tertiary 
beds is structurally involved in the mountains, and is known to extend north¬ 
ward some distance along the valley of the Newton. The rocks are to be 
expected also to outcrop in the Deepdale basin, but the writer did not hear 
of their occurrence in this difficultly accessible valley. 
A much wider zone of argillaceous and calcareous beds standing at high 
angles occurs to the eastward of the Sphinx Rock area. It extends north¬ 
ward across the Buller along the western side of the Matiri Valley, reaching, 
it is reported, as far north as Lake Matiri, eight miles from the Buller. The 
beds of this zone, though, as a whole, decidedly less calcareous than those 
that form the Sphinx Rock, undoubtedly belong to the same series. As 
the strata are followed upward they are seen to pass into soft blue argil¬ 
laceous sandstone, a rock which does not appear to be represented in the 
Sphinx Rock section. 
The rocks described in the preceding paragraph form the hills overlook¬ 
ing Murchison on the western side of the Matakitaki, but the steep ridges 
on the opposite side of that river have been carved from beds of conglomerate. 
Thick highly inclined layers of this rock alternate with thinner beds of 
argillaceous sandstone, blue mudstone, and carbonaceous shale, and out¬ 
crop as parallel rocky ribs on the grassy slopes that face the Buller for two 
miles below the confluence of the Mangles. The Buller occupies a narrow 
valley along the strike of these rocks for eight miles, but the Mangles, flow¬ 
ing from the eastward, cuts across their upturned edges. The conglomerates 
extend up the latter stream as far as Blue Duck Creek, but beyond this 
* The map referred to appears in 11th Ann. Rep. N.Z. Geol. Surv., C.-2b, 1917. 
