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Rocks East and South of Mount Lay

The mountain east of Mount Lay and the ridge 3 miles northeast of
Mount Lay are composed of interbedded limestone and chlorite-sericite
slaty rocks, with minor chloritic quartzites. East of Mount Lay, limestone
is almost continually exposed for a stratigraphic thickness of 1,200 feet.
Most of the limestone is blue-grey to light grey, massive, with irregular
patches or beds of ivory-coloured recrystallized calcite. Ivory or pale
rose-coloured, muscovite-rich, sugary limestone, in beds up to 4 inches thick,
separated by bright green, soft, chloritic slates or crumpled chloritic
phyllites, occur in many places throughout this assemblage. Beds of cream-
coloured finely crystalline limestone an inch or two thick, separated by
bright purple partings a fraction of an inch thick, make a conspicuously
banded rock characteristic of much of the Ingenika group strata in this
area (See Plate VII A). The chloritic schists, slates, and phyllites are all
more or less calcareous.

In the mountains south of Swannell River Valley, south and southeast
of Mount Lay, much the same general assemblage of limestone, chloritic
phyllites, and slate is found. Relatively pure white quartzite, in beds up
to 40 feet thick, forms the greater part of a small knoll about 4 miles
south of Mount Lay. On the mountain southwest of Mount Lay, four
bands of blue-grey, massive to bedded, non-slaty limestone, about 100 feet
thick, are separated by 100 to 500 feet of black, dark grey, and brown,
slaty limestone, and grey-green slaty calcareous schist, chlorite schist,
quartzite, and grit. Some of the limestones have been recrystallized into a
fine-grained variegated marble. Ivory-coloured, sugary, micaceous lime-
stone, in thin beds separated by partings of bright green chloritic slate, is
widely distributed throughout this assemblage, but comprises only a small
part of the total rock.

Rocks in Upper Swannell River Valley

The same general sequence as that south of Mount Lay was observed
in the valley of Swannell River west of Orion Creek, where the interbedded
limestone-chloritic slate assemblage is underlain by about 3,000 feet of
schist, slate, quartzite, quartzitic grit, and conglomerate. A distinctive,
grey-green, schistose, quartzitic conglomerate or grit is abundant in this
locality. About one-third of the typical grit consists of rounded, somewhat
elongated grains of bluish grey quartz, 7s to $ inch in diameter, and scat-
tered grains of white feldspar up to »; inch in diameter, in a schistose or
phyllitic matrix composed essentially of quartz, sericite, and chlorite. Some
beds of this rock contain numerous streaks of limonitic material.

Ingenika group rocks are exposed continuously from Orion Creek north-
west to the west border of the map-area. The proportion of calcareous
material decreases toward the west. Some of the lowermost beds of this
section contain scattered flakes of biotite, and a few porphyroblasts of
garnet.

Rocks in the Northern Third of the Map-area

All of the rocks in Aiken Lake map-area north of the belt of Tenakihi
group rocks exposed in the core of the anticlinorium that stretches from
Mesilinka River at the east border of the map-area to Wrede Creek at the
west border, except for a small area of the Sifton formation in the floor of