12

A section 700 feet thick of lavas referred by Dawson to the Lower
Volcanics was measured in Fraser canyon at 17 Mile ranch (Figure 2,
locality 38). It consists of beds of dark-coloured basalts and andesites
with lighter coloured dacites and a nearly white dacite tuff on top (Plate
XII). These beds lie in a broad syncline whose axis trends about north

- 20 degrees west. The rocks are much faulted, brecciated, and altered
to clay.

The following is a geologically ascending section taken across the strike
from east to west. Samples of the rock from beds Nos. 2, 5, 10, 12, 13
14, 15, 16, and 21 were examined under the microscope.

Thickness in feet.
1. Just east of railway track back of first cliff, andesitic lavas strike
south 28 degrees east, dip 60 degrees to the east, practically
Stee isi) cic a] ogee pests sf g Are Se 5 fos n Ree ters nip ee Semen ent 5 eer ry Bn 30
2. Red basalt showing flow structure and forming a cliff, only slightly
REE CREO or a en oo oe el Eg ee eee ee 50 to 100
3. Platy basalt weathering greenish brown, strike south 2 degrees
west, dip 70 degrees wést................ eS oe see eae 6 to 10

4. Dark-coloured lava altered to a red crumbly mass; the strike of the
boundary between this and the succeeding bed is south 28
MERTCEs CHAU i grees oss cs PhS ee ee een 25
5. Dark grey andesites and red lavas, probably basalt cut by faults,
one fault dipping west at about 20 degrees. The beds are much
disturbed and in places largely changed to clay. The railway
cuts through this zone. A sample of clay from beside the track

was tested for its value as building brick ................... 15
Ge ici encuncder tlie warton TORU. ccna. Se ic sg Ge ree s ee ee 95
7. Very basic lava weathering to a green brown clay............... 30
8. Much altered andesite or trachyte, altered toward top to a yellowish
clay. The unaltered stone in fragments } to 3 inch in size, forms
— about 15 per cent of the mass at the surface. Zones 7 and 8
form a 35 to 60-foot bank in places....................-- Fe ~~ 50
9. Andesite or basalt altered to a brownish green clay. A good deal
of this bed is of undecomposed rock.........5....-5-.5..005- 20
10. Red basalt weathering, in places only, to a red ochre. This bed
appears to have been faulted locally. A sample of the more
decomposed material was tested for its value as mineral pigment 10
dt. Porpush clays: en ee ee ee Se one ee 5

12‘ Grey-white andesite weathering to a yellowish white clay which is
extremely sticky when wet. A very large proportion of the
outcrop is clay. For a distance along the strike of at least 200
yards several thousand cubic yards are available. A sample of

clay from this bed was tested for building brick.............. 12 to 15
13. Grey dacite not as much decomposed as No. 12 forming cliffs
which: are-traversed by-faults: 2220.2... ag ice. wht 15 to 20

14. Pink-grey andesite very largely decomposed to clay, strike south
31 degrees east, dip about 75 degrees to east. This dip may be

Of ONly local SIPMINUANEE 6s eee So ss ese ES 15
15. Red-brown andesitic agglomerate largely weathered to a purplish
- brown clay. Fragments resembling Cache Creek quartzite were
seen in microscopic sections. The clay is not uniform in appear-

ance. A sample was tested for its value as a mineral pigment. . 30
-16. White volcanic ash with a band of finer texture in it. This is of the
composition of dacite and weathers to a gritty clay............ 36
17. Dark brown basalt weathering to purplish clay................. 415
18. Andesite or dacite weathering white and green.................. (2)
19. Alternating lava or ash beds of varying composition mostly weather-
ed to clay and more or less covered... 00... oe ee ee es 150
20. Fresh, hard, mauve andesites or tuffs.....00:.....0.. 500.000. 008. 15
Dark grey qnaestester tule. 3 Sass bd oe Sets 15
POLAR DICKNOSS. 3s eo ee eae 639 to 701