Speight. — The Older Gravels of Nerrth Canftrbury. 211 



on the river-banks ; but the dip becomes steeper till, on the face of a high 

 bluff below the bush, it reaches 20°. Here are alternating sandy clays and 

 gravels, the former greenish-yellow in colour, which are capped unconform- 

 ably by somewhat irregular sands and gravels, lying almost horizontally 

 across the denuded edges of the lower set. The upper series evidently 

 forms the distinct ridge which leads down-stream past the point where the 

 undoubted unconformity described above was observed. 



Similar beds are observed in places on the banks of the stream higher up, 

 but the covering of bush and soil is too complete to attempt a correlation 

 with those lower down. Owing to this covering it is likewise impossible to 

 say whether the junction between the greywackes of Mount Grey is a simple 

 unconformity or a fault contact. 



Kowai River, South Branch. 



The high banks of this river rise in places to a height of 500 ft. above 

 its bed, frequently with precipitous faces, and thus excellent sections are 

 exposed. The strata are also folded into gentle anticlines and synclihes, 

 so that in the cores of the former the lower beds are exposed. They consist 

 of the following in ascending order : — 



1. Sands with concretionary layers, with broken-shell beds in the lower 



part, at least 80 ft. thick. 



2. Green sandy clays and greivel beds, the latter finer in grain and thicker 



in the lower part, and cemented with iron oxide. 



3. At higher levels there are rapidly alternating gravel and sandy 



beds, the former composed of subangular pebbles, which point to 

 deposit either on a land-surface or on a shore-line in close 

 proximity to the source of supply. No limestone pebbles were 

 seen in these beds. In places they exhibit intraformational uncon- 

 formities, such as one would expect when rapid changes in the 

 conditions of deposit take place, especially when the change is 

 from a sand to a gravel, and vice versa. The gravel beds fre- 

 quentlv form steep cliffs ; and their hard bands determine the 

 dividing-ridges between the tributary streams running into the 

 main river, especially on the south side, and they also determine 

 an important reach of the river itself, although its direction is 

 primarilv across the strike, and therefore of consequent character. 

 A speciallv good section is to be seen where the river makes a right- 

 angle turn, and changes from the subsequent to the consequent direction. 

 The beds are here bent up into a rather sharp anticline with a north-east 

 strike and a dip to the north-west at an angle of 50°. On the seaward side 

 of the anticlinal axis the dip is much less, the angle being about 10°, the 

 succession being similar. But farther down-stream the strike swings round 

 till it is north-north-east, then north-north-west, and finally north-west, 

 following for a time the direction of the main river. This allows the lower 

 members of the series to be exposed again in the bed and banks of the river. 

 They consist here of sands and sandy clays, greenish-blue in colour and 

 weathering brown, containing fossils, some of the sands with concretionary 

 layers and associated with thin gravel beds. The shells consist of Siphonedia,^ 

 Glycymeris, and Ostrea, but in a fragmentary condition. 



Farther down-stream the greenish-blue beds are still exposed, but the 

 strike gradually becomes north-east with a dip to the south-east, and 

 gravel beds form the greater part of the high bluffs which face the river 

 on the north above the Mount Grev Station. 



