1920.] 
Speight.—Broken River Coal Area. 
93 
THE GEOLOGICAL FEATURES OF THE BROKEN 
RIVER COAL AREA. 
By R. Speight, M.A., M.Sc., F.G.S., F.N.Z.Inst., Curator of the 
Canterbury Museum. 
. T -. Contents. 
A. Introductory. 
B. Physiography. 
C. Stratigraphy :— 
1. Maitai Series. 
2. Waipara Series— 
(a.) Descriptions of Sections : Alum Creek, Broken River, Winding Creek, 
Iron Creek. 
(b.) Structure of the Coal-measures. 
(c.) Quality and Quantity of the Coal; Conditions of Deposit. 
(d.) Volcanic Rocks. 
( e .) General Relations to Neighbouring Areas. 
3. Sloven’s Creek Beds. 
A. INTRODUCTORY. 
The Broken River coal area, which has recently been opened up com¬ 
mercially as a source of household and steam coal, presents certain geological 
features which are worthy of record ; and all the more is this the case since 
opportunities for careful examination are afforded while working is actually 
going on, which will not occur when the region has been exhausted of coal. 
The area lies in the heart of the mountain region of Canterbury, about four 
miles from the Avoca Station, on the Midland Railway, and is distant about 
sixty miles from Christchurch. Access to the field is obtained from the 
Avoca ^Station by a short line of railway, as well as by a foot and pack 
track. Both these routes climb up the steep terrace out of Sloven’s Creek, 
and follow along it for about a mile, and then descend into the gorge of 
Broken River and follow it to the vicinity of the mine. 
B. PHYSIOGRAPHY. 
(See Figs. 1 and 2.) 
The area under consideration forms part of one of the intermontane 
basins of the Canterbury alpine region (Speight, 1915, p. 341), which owe 
their dominant features to structural causes. The height of the floor of the 
mid-Waimakariri basin, in which the area is situated, varies between 1,600 ft. 
and 2,500 ft., but from this floor isolated peaks and ranges rise to nearly 
5,000 ft., whereas the ring of mountains which borders it reaches to just over 
7,000 ft., and long stretches are over 6,000 ft. The form of the basin was 
modified considerably by glacier-action, and numerous extensive deposits 
of moraine occur ; those within the boundaries of the coal area are, how¬ 
ever, of somewhat limited extent, the evidence' for glaciation being chiefly 
the presence of abraded surfaces and general landscape forms. Immediately 
to the south and east of the area one of these abraded surfaces forms a 
distinct shelf or terrace which has been deeply dissected, but the remnants 
are sufficiently extensive to give a clear indication that it once formed 
part of the floor of the basin as it was left on the retreat of the ice. 
Remnants of the outwash of the rivers issuing from the glacier-fronts as 
they retreated separately up the valleys as the ice epoch was passing away 
