1920.] 
Speight.—Broken River Coal Area. 
99 
Above this level the face is obscured by both bush and talus material, 
so that the sequence can better be continued from the section in close 
proximity to it in Alum Creek. 
On following up the course of Alum Creek one encounters greywacke 
for about 5 chains and then the coal-measures. These form the slopes 
on both sides of the creek, but the clearest exposure is obtainable in the 
slip that forms its western side (fig. 4), the eastern side being somewhat 
obscured by surface creep and by loose material. Starting from the mouth 
of the main drive in the bed of the creek, the following sequence occurs 
as the outcrops are followed up the slip, the thicknesses given being only 
approximate :— 
1. Coal, 9 ft., striking north and dipping west 75°. 
2. Sandy clays and impure lignite, 75 ft. 
3. Sands, 40 ft. 
4. Coal and shale, 12 ft., striking N. 15° E., dipping west 75°. 
5. Sands, sandy clays, with numerous small seams of shale and lignite, 
80 ft. 
6. Impure lignite, 8 ft., striking N. 15° E., dipping west 35°-40°. 
7. Sands, sandy clays, and fireclays, 75 ft. 
8. Impure lignite and shale, 12 ft. 
9. White sands and sandy clays, 40 ft. 
10. Impure sandy lignite, 12 ft. 
11. Sands and sandy clays, 25 ft. 
12. Impure lignite, striking N. 25° E., dipping west 45°* 
13. Sand and sandy shale, 50 ft. 
14. Impure lignite, 1 ft. 
15. Sands, sandy clays, and fireclay, 35 ft. 
16. Sands and impure sandy shales, 150 ft., striking north-west, dipping 
south-west 20°. 
17. Sands and sandstone, 500 ft. (estimated), dipping south-west 35°. 
These beds are capped unconformably by terrace gravels, while on the 
south side of the belt of bush which fringes the cliff morainic heaps also 
occur. 
On the eastern side of Alum Creek the exposures are not clear, but it is 
evident that the strata are much disturbed. Bed No. 1 in the series just 
given is bent over into an anticline whose axis lies in the bed of the creek, 
but there is a reversal of dip, and a small syncline flanks the anticline on 
the east. When followed north in the mine the steep dip of this bed flattens 
out, and the seam almost joins with that numbered 4, and when traced a 
little farther it disappears, which is also the case as it is traced south for 
about 5 chains. The sudden terminations in both cases cannot be attri¬ 
buted to faulting, but to the fact that the coal was not deposited, or, if so, 
it was cut out before the succeeding beds were laid down. This irregularity 
is also exemplified by a large seam on the eastern slope of Alum Creek, 
some 12 ft. thick where exposed on the surface, which does not appear at all 
in a drive at a depth of 35 ft. below the surface. This emphasizes the marked 
irregularity of the beds, a fact which is noticeable in all parts of the coal¬ 
bearing area. 
This feature is displayed in the drives put in on the west side of Alum 
Creek. The case of bed marked No. 1 has been referred to, but the case 
of No. 4 is also important. When followed north, then west and south 
along the levels of the mine, the strike of the seam is found to swing 
round till the dip is to the east at a point about 3 chains south¬ 
west of where the seam has been cut in the main drive. As the seam 
swings round in its farthest northward extension it thins out so as 
