358 Transactions. 



Poliniees, Turritella, &c, which could be identified in situ, indicated that the 

 beds were probably of mid-Tertiary age. One isolated boulder found in the 

 bed of the stream was full of the black oyster-shell which occurs in beds 

 at the base of the Tertiary .series in the Trelissick Basin and elsewhere in 

 Canterbury ; indeed, the former area is in comparative proximity, since 

 it is on the other side of the Craigieburn Range, which flanks the valley 

 on the south, so that it is very probable that the lower members of the 

 Tertiary series are also represented in the valley of the Harper. 



The beds are best developed on the south-eastern side of the "valley, 

 but they also occur on the north-west side as well. They are, however, 

 forest-clad in many parts, covered with moving debris from the neighbouring 

 grevwacke hills in others, and in all places subject to slumping movements, 

 so that their relations to one another are difficult to make out. The strike 

 of the beds is in a north-east and south-west direction, with a dip to the 

 south-east, the strike being approximately coincident with the direction 

 of the valley. Near the mouth of the Avoca there is the most remarkable 

 case of weathering into pinnacle forms that I have ever seen. 



The only satisfactory solution for the occurrence and position of these 

 Tertiary beds is that they have been faulted down from a higher level and 

 thus escaped the erosive action of frost and ice, which has in all probability 

 removed the connecting masses from higher levels, the beds forming 

 originally a part of the great covering of Tertiary sediments which masked 

 the old peneplained surface of the mountain region at the close of the 

 Tertiary era. It is noteworthy also that this occurrence marks the farthest 

 extension of these beds to the axis of the main range in the northern 

 part of Canterbury ; and, as undoubted marine beds are in evidence, it 

 clearly shows the trail sgression of the sea far inland during late Tertiary 

 times. 



If a fault origin for the occurrence is admitted, then it is easy to explain 

 the straight alignment of the valley-walls, and. further, the extension of 

 that alignment into the valley of the Cass over the saddle— a feature to 

 which 1 have previously drawn attention, and suggested for it a structural 

 origin.* The Cass Valley and the Harper are thus located on an old fault- 

 line running north-east and south-west, and parallel to those occurring 

 in the Esk River Valley, and in the valley of the Upper Porter River, and, 

 in a wider sense, to the system of fractures oriented in the same direction 

 which affect a large part of the north-eastern region of the South Island, as 

 pointed out by McKayf and Cotton,! and called by the latter the Kaikoura 

 system of fractures. 



The general arrangement of the beds in the Harper Valley, and its 

 characteristic form, are strongly reminiscent of valleys of similar origin 

 in the north-east part of the province, such as the Greta and Waikari 

 Vallevs, and, on a small scale, of the great structural valleys of the Kaikoura 

 region. The relative movement of the recks has resulted in an apparent 

 downthrow of the beds to the north-west, and the same is true in the 

 case of the Harper, so that this movement has extended far inland into 



* R. Speicht, The Physiography of the Cass District, Trims. N.Z. Inst., vol. 48, 

 191G. p. 148. 



I- A. McKay, On the Geology of Marlborough and South-east Nelson, Rep. Geol. 

 Explor. dur. 1890-91, 1892, pp. 1-28. 



J ('. A. Cotton, The Structure and Later Geological History of New Zealand, Geol. 

 Mag.. 11)11). p. 248 et seq. 



