Uttley. — Tertiary Geology, Otiake River to Duntroon. 137 



Art. XXII. — Tertiary Geology of the Area between the Otiake River 

 (Kurow District) and Duntroon, North Otago. 



By G. H. Uttley, M.A., M.Sc, F.G.S., Scots College, Wellington. 



[Read before the Wellington Philosophical Society, 18th September, 1918 ; received by 

 Editor, 31st December, 1919 ; issiied separately, 15th June, 1920.] 



Contents. 



I. Introduction. 



II. General Description of the Area. 



III. Historical Summary. 



IV. Description of the Tertiary Beds. 



(1.) Trigonometrical Station Z, Otiake River. 

 (2.) Otekaike Special School. 

 (3.) White Rocks and Duntroon Area. 

 (4.) Maruwenua* River. 

 (5.) Station Peak. 

 V. Structure of the Area. 

 VI. Conclusion. 



I. Introduction. 



As will be seen from the accompanying geological map (fig. 1), the area 

 described in this paper extends from the Otiake River, the southern 

 boundary of the Kurow Survey District, to near Duntroon, on the Otago 

 side of the Waitaki River. The district north-west of the Otiake River is 

 dealt with in a later paper in this volume, but to save unnecessary repeti- 

 tion a full historical summary of the work of previous observers in that 

 area, as well as in the present area, is given below. 



In the geological map no attempt has been made to map the various 

 types of gravels, as the delimitation of their boundary-lines and their dif- 

 ferential characteristics will demand a great deal of detailed work. The 

 gravel lands are now covered with vegetation and soil, and this fact 

 renders their distinction difficult. The Wharekuri-Otekaike fault, which 

 bounds the Kurow tilted block, follows an almost straight line, but 

 between the Otekaike basin and the Otiake basin, a spur of the undermass, 

 dipping easterly at 6° beneath the Tertiary rocks, apparently breaks the 

 continuity of the main fault-line. It would appear that in this locality 

 the low-lying block had failed to break away, as the stripped surface of 

 the spur is certainly continuous with that of the uplifted block for some 

 distance to the west of the main line of faulting. No convincing evidence 

 was obtained to show whether the boundary scarps of this protruding 

 spur were fault-scarps or fold-scarps, except in the neighbourhood of 

 Newsome's Creek, where the quartz-grits were found lying directly on the 

 sloping surface of the undermass on the southern side of the spur, three- 

 quarters of a mile east of Trig. Station D. The surface and overlying 

 quartz-grits at this point dip southerly at 30°, indicating that, in this 

 locality at least, the scarp is a fold-surface. 



McKay was the only geologist who investigated the area in any detail, 

 and the sequence of rocks as recorded by him was characteristically 

 accurate. His classification of the sediments was based almost entirely 

 upon lithological characters, but he made large collections of fossils from 

 several parts of the Waitaki Valley, and these were determined by the late 

 Mi. Henry Suter two or three years ago, but the lists have not yet been 

 published. McKay's account of the geology is rendered somewhat difiicult 



* Spelt also " Maerewhenua " and " Maraewhenua." 



