1920 .] 
Speight.—Broken River Coal Area. 
151 
vicinity of the Avoca Railway-station and farther up the stream towards 
the present Craigieburn Station. The stratigraphy of this outlier is com¬ 
plicated by the presence of these barriers and by volcanic disturbances, 
but more detailed description will be given of this area later, as it has a 
close geological connection with the area farther west. 
The absence of limestones, as compared with their great development 
in the Castle Hill area and in the valley of the Esk, can be partly explained 
on the supposition that they have been removed from the eastern portion 
of the intermontane basin by erosion after they have been deposited, pro¬ 
bably by glacial erosion, seeing that the middle part of the area experienced 
the full force of the glacial streams issuing from the higher valley of the 
Waimakariri, whereas the Esk River valley and the Castle Hill district 
were beyond the sphere of its great activity. That some such action has 
taken place, and that some part of the limestones has been removed, will 
be evident when certain inclusions in tuffs and gravels belonging to the 
Sloven’s Creek area are considered. 
On the other hand, limestones may never have been deposited in the 
south-eastern part of the intermontane basin, since the shore-line of the 
sea where deposition occurred almost certainly lay near its eastern border, 
and the marine deposits of that locality would in consequence be of littoral 
or estuarine character. It must always be remembered as well that the 
surface features of the land were entirely dissimilar from those now obtain¬ 
ing, and the area probably formed part of a peneplain which has since been 
elevated into the alpine region of Canterbury. 
Whether the limestone was deposited or not, the Broken River coal- 
measures are of the same age as the lower members of the series developed 
in the Trelissick Basin, and correspond with the coal-beds near Old 
Craigieburn. This is clearly seen by the similarity in the lithological 
character of the beds, and also by the presence of Conchothyra in both 
localities in beds overlying the coal conformably. 
This occurrence is one of the many small outliers of what Thomson 
calls the Notocene beds, found in various parts of Canterbury at heights 
varying from 1,000 ft. to 4,000 ft. and higher still, which indicate an 
original widespread mantle of late Cretaceous and Tertiary sedimentaries 
over what is now a mountain region. In order to emphasize this point I 
have tabulated the occurrences in the valleys of the various rivers issuing 
from this region. 
Waimakariri— 
Lower valley of the Esk River. 
Trelissick Basin. 
Broken River coal area. 
Craigieburn. 
Sloven’s Creek. 
Benmore. 
Rakaia— 
Acheron River. 
Glenthorne. 
Harper River. 
Redcliff Gully. 
Cameron River, near Lake Heron. 
Upper Cameron River. 
Teddy’s Hill (4,000 ft.). 
Smite River. 
