340 Transactions. 



of prominent cuestas, of which that of the main Mount Brown limestone 

 (c/. fig. 2) is the highest and most persistent in the middle part of the strip, 

 iDeing breached only by the Waipara River and the Weka Creek. In the 

 south-western part of the district the most prominent cuesta is that of the 

 lower Mount Brown limestone, while east of Mount Donald the Weka Pass 

 stone cuesta rises to equal prominence with that of the main Mount Brown 

 limestone. Although subsequent depressions between the main cuestas were 

 well developed, these were mostly occupied by small tributaries of various 

 consequent or insequent streams, and there are few subsequent streams of 

 any importance. The soft Piripauan beds and " grey marls " were for the 

 most part reduced to low rehef, and on them the Waipara River and Boby's 

 Creek, and to a less ext6nt the Weka Creek, developed broad flood-plains 

 and meandering courses. The texture of dissection of the more porous 

 Notocene was much coarser than that of the higher-standing pre-Notocene. 

 which was characterized by numerous insequents with many rocky ledges. 



North-east of Mount Donald the pre-Notocene rocks of Moore's Hills 

 preserve fairly perfectly a fossil peneplain similar to those described by 

 Cotton from Oamaru, Central Otago, the Gouland Downs, &c., including 

 the presence on it of a small outlier of Weka Pass stone. No similar fossil 

 peneplain appears to exist on the Doctor's Range, although the even slope 

 from the height of the range to the saddle north of the Deans seems, when 

 seen in profile, to suggest the presence of such a stripped surface. The 

 reason for its absence near the Doctor's Gorge may possibly be the steepness 

 to which the base of the Notocene has been tilted at this point, rendering 

 it more liable to erosion ; but, as the stratigraphy shows the existence 

 of an overlap during the deposition of the Piripauan and Kaitangatan, it 

 appears more probable that the surface on which the Piripauan rests was 

 not peneplained, though peneplanation had become practically perfect on 

 the adjacent land before deposition of the Weka Pass stone. 



The mature topography above described has been modified by a later 

 revival of erosion due to regional uplift, which has allowed the Waipara 

 River, the Weka Creek, and their main tributaries to incise themselves more 

 than 100 ft. in the old flood-plains in narrow steep-walled gorges. The 

 revival extends in the main streams right through the Notocene strip and 

 into the adjacent parts of the pre-Notocene rocks, but in the smaller, ste'ep, 

 and mostly dry tributaries draining the back of the cuestas of the Mount 

 Brown and Greta beds has not passed, on the average, more than half their 

 lengths, and the lower gorges through the Kowhai gravels and upper part 

 of the Greta beds end abruptly in sand or gravel chffs. Incised meanders 

 are a marked feature of the rejuvenated topography,- and are well displayed 

 in the Waipara River both above and below the limestone gorge, and in 

 Boby's Creek, while a beautiful example, superimposed on the pre-Notocene, 

 is shown in the upper of the two inliers of those rocks in Bell's Creek. In 

 the Waipara River the revived valley is graded right through the Notocene 

 strip, but in Boby's Creek and Weka Creek the grading is not so perfect, 

 and in the former the Ostrea beds cause a waterfall of about 20 ft. 



The uplift which led to this revival is doubtless the same as- caused the 

 raised beaches of 150 ft. and 2.50 ft., described by Speight (1912), near 

 the mouth of the Waipara River. Its discontinuous nature is shown by a 

 flight of terraces in the Waipara River above the linfestone gorge, as 

 figured by Cotton (1919) and shown in Plate XVI. Witness to its recent 

 origin is also borne by numerous cut-off meanders at various heights in 

 Boby's Creek. 



