• Wild. — Geology of the Bluff. 317 



Art. XXXV. — The Geology of the Bluff, New Zealand. 



By L. J. Wild, M.A. 



Communicated by Dr. P. Marshall. 



[Read before the Otago Institute, 3rd October, 1911.] 



1. Introduction and Description of the Topography of Area. 



The generally even surface of the Southland Plain is broken on its 

 coastal margin by a range of hills extending in a south-easterly direction 

 from the mouth of the New River Estuary for a distance of seven miles, 

 and terminating in Bluff Hill. The height varies much from point to 

 point, but the outstanding feature is Bluff Hill, which attains an elevation 

 of 860 ft. 



Several geologists have visited the locality, or have examined speci- 

 mens of rock from it, but the area has never been submitted to accurate 

 and systematic geological examination. 



Hutton,* in 1872, referred to the Bluff Hill in describing the 

 geological structure of the Southland District. He also described the 

 relative positions of some of the rocks found there, and such of their 

 characters as can be detected in the field. In his " Geology of Otago," 

 published in Dunedin in 1X75, he repeated the conclusions he had 

 come to. 



In 1888 the general structure and physiographical nature of the 

 district was described at some length by Park,f who also went into the 

 evidence as to the age of* the rocks; but the writer offered neither 

 chemical nor microscopical descriptions of the various rock types. 



At a later date Huttonj named and described sections of specimens 

 of rock from Bluff Hill, but subsequently, with more material at hand, 

 published additional notes, § in which he expressed a change of opinion 

 with regard to the nomenclature of some of them. It is rather unfor- 

 tunate that the localities from which these specimens were obtained have 

 not been recorded more definitely. 



Hamilton|| has also contributed to the literature on the subject, and 

 the locality is also mentioned several times in " The Geology of Otago," 

 by Hutton and Ulrich. The references in the latter publication will be 

 discussed below. 



Thomson^ has recently published notes on some rocks which are " the 

 result of a few hours' collection along the shore south and west from 

 Bluff Harbour," and "from a small headland about half a mile round 

 the coast to the south-west just beyond the mouth of the harbour." A 

 glance at the map will show that " west " must be a misprint for " east." 



* Hutton, " Report on the Geology of Southland," Rep. N.Z. Geol. Surv., 1871-72. 

 p. 89. 



t Park, " On the Geology of Bluff Peninsula," Rep. N.Z. Geol. Surv., 1887-88. 

 p. 72. 



X Hutton, " Notes on the Eruptive Rocks of Bluff Peninsula," Trans. N.Z. Inst., 

 vol. 23 (1891), p. 353. 



§ Hutton, " Corrections of the Names of some New Zealand Rocks," Trans. N.Z. 

 Inst., vol. 31 (1899), p. 484. 



|| Hamilton, " Notes on the Geology of the Bluff District," Trans. N.Z. Inst., vol. 19 

 (1887), p. 452. 



Tf Thomson, J. A., " Notes on some Rocks from Parapara, Bluff Hill, and Waikawa," 

 Trans. N.Z. Inst,, vol. 42 (1910), p. 33. 



