336 Transactions. 



Structure. 



The general geological structure of that part of North Canterbury within 

 which the district lies consists of elevated folded or tilted blocks with a 

 general north-east and south-west trend, separating lowland areas which 

 in the interior are interniont depressions. Broadly speaking, the elevated 

 blocks may be regarded as anticlines and the depressions as svnclines, 

 though they are in many places bounded by faults on one or other side. 

 The folding and faulting has been of geologically young age, after the close 

 of the Notocene deposition, and is doubtless due to the same (Kaikoura) 

 orogenic movements as caused the elevation of the Kaikoura Mountains. 

 Since these movements erosion has largely stripped the Notocene cover 

 from the higher parts of the anticlines or tilted blocks, so that it is now 

 found only on the lower slopes, and the resulting deposition has partiallv 

 filled the synclines or fault-angles with horizontal Notopleistocene alluvium. 



One such lowland area is the Amberley-Waipara Plain, which is a northern 

 continuation of the Canterbury Plain, from which it is nearly cut off by 

 the Moeraki Downs, consisting of tilted late Notocene gravels. This plain, 

 135 ft. above sea-level at the township of Amberley, and 231 ft. at the 

 township of Waipara, slopes down south-east of the former place to low 

 cliffs near the sea, but farther to the north-east it leaves the coast and enters 

 an elliptical basin, crossing the Waipara Eiver and extending some distance 

 up the ^tributary Omihi Valley, being separated from the sea by the anti- 

 clinal elevation of Mount Cass. The lowland area extends farther to the 

 north-east than the actual alluvial plain, and passes by way of the Greta 

 Valley into the lower Hurunui Valley. 



A second lowland area, farther inland and roughly parallel to the first, 

 is the Hurunui-Waiau intermont basin, 567 ft. above sea-level at Culverden, 

 which is drained by the Hurunui and Waiau Rivers. The south-western 

 extension of this basin reaches the upper Waipara River near Heathstock,- 

 while a small lateral extension on the south-east side reaches the head- 

 waters of the Waikare River near the township of Waikare, 733 ft. above 

 .sea-level. 



The elevated belt separating these two lowland areas is divided by 

 transverse depressions into three main blocks — viz., Mount Alexander 

 (2,448 ft.) to the north-east, the Doctor's Range (2,568 ft.) in the middle, 

 and Mount Grrey (3,055 ft.) to the south-west. The north-easterly part is 

 again divided obliquely by a nearly east-west fault, which runs from the 

 neighbourhood of Waikare along the south side of the Waikare River, and 

 separates a subsidiary low block, Moore's Hills, on the south from the 

 higher Mount Alexander block to the north. The lowland area between 

 these two blocks is occupied by the Waikare Valley, and is continuous 

 at its head with the lateral extension of the Hurunui-Waiau intermont 

 depression, forming the northerly of the two transverse depressions in the 

 elevated belt. The southerly transverse depression is the fault-angle of a 

 nearly north-south fault on the eastern side of Mount Grey, which lies on 

 the upthrown side of this fault. 



The Middle Waipara and Weka Pass district here described forms the 

 lower south-easterly parts of this discontinuous elevated belt between the 

 two main lowlands. The Notocene strip of which it is composed is bounded 

 on its inland side by a fault near Mount Grey, rests unconformably on the 

 pre-Notocene of the Doctor's Range, is thrown into a series of folds between 

 the Weka Creek and Waikare, and at this point has not been completely 

 stripped from the anticline of old rocks, and is again bounded by a fault 



