THOMSOJSf. — Geology of Middle Waipara and Weka Pass District. 337 



south of the Waikare River except for a few miles where it has again been 

 stripped from the pre-Notocene on the summit of the Moore's Hills block. 

 On its seaward side the Notocene strip everywhere dips under the Noto- 

 pleistocene gravels of the Amberley-Waipara Plain. The Notocene beds 

 are, with the exception of the Kowhai gravels, an accordant series, and 

 behave as a structural unit in regard to folding and faulting. The general 

 type of structure is shown diagramniatically in fig. 2. 



Prs-Notooene. Piripauan- 'Amupi limestone and' '"Gray maris " and" Greta beds.' 



Weka Pass store. Mojnt Brown beds. Kowhai t>ed3. 



Fig. 2. — A diagrammatic section from north-west to south-east across the district. 



The disposition of the Notocene rocks as a simply tilted series with 

 dips to the south-east is modified at various places both by faults and 

 folds. The more important of these are the Mount Grey fault, bounding the 

 Notocene to the south-west ; the Boby's Creek fault, cutting the Noto- 

 cene strip obliquely and separating the Mount Brown area from the 

 remainder of the strip ; and a series of folds transverse to the strip on 

 the north-western side of the Weka Pass. 



Doctop's Ranse. 



Waipara River. Boby's Creek. Mount Brown 



^y//A'/////A 



// ■ Pre-Notocene.V '^'</ 



0'///y//^ ////// 



// /////// / // / / / / 



Fig. 3. — Section across the Bobv's Creek fault. 



The displacement along the Mount Grey fault is very great^ — probably 

 over 2,000 ft. — but cannot be accurately estimated, as the Notocene rocks 

 do not occur along the upthrown side. There must have been considerable 

 drag accompanying the formation of this fault, for the limestones of the 

 Notocene, which half a mile north-east of the fault-line strike north-east 

 with a moderate dip to the south-east, become practically vertical near 

 the fault-line and curve round to strike north-north-west. 



The Boby's Creek fault runs west from the Waipara River north-east of 

 Mount Brown, across the lower part and into the upper part of Boby's Creek, 

 ending against the Mount Grey fault. The dow)ithrow is on the north and 

 east side, and amounts to about 1,300 ft. near the middle, where the " grey 



