318 



Transactions. 



The present paper will aim principally at an accurate description of 

 the rocks that outcrop on the portion of the foreshore of Bluff Harbour 

 lying between the wharves and Starling Point, together with the related 

 rocks of Tewaewae Point, since this area exhibits in most striking manner 

 the different rock types and their mutual arrangement. 



The more detailed investigations herein described point to conclusions 

 somewhat opposed to previously accepted ideas of the geology of the 

 district. 



Position . 



The Bluff Range forms the backbone of a prominent peninsula of 

 the south coast of the South Island of New Zealand, in latitude 46° 32' S. 

 and longitude 168° 23' E. It extends for seven miles from north-west 

 to south-east. It is united to the mainland by a narrow strip which 

 projects to the east from the flank of the range at its north-western end, 



Fig. 1. — Map of the Bluff District. 



and separates the waters of Bluff Harbour on the south from the Moko- 

 moko Inlet on the north. At its north-western extremity the range 

 terminates in somewhat abrupt cliffs impinged on by the New River, 

 the mouth of which has been driven east by the sands of the Riverton 

 Beach, which are constantly travelling in this direction under the 

 influence of the seas and currents caused by the prevailing westerly 

 winds. 



Origin of the Land- forms. 



The range consists of a mass of igneous rock which was originally a 

 deep-seated intrusion. Subsequent denudation acting more readily on 

 the intruded than on the intrusive rocks has exposed the intrusive mass 

 as a range of hills. The area of contact, which is fully described in 

 the following pages, is thus a metamorphic aureole. The resulting meta- 

 morphic rocks outcrop in places as the base of the range on the north-east 

 side, the most extensive outcrop being on the foreshore of the harbour 

 from Henderson Street for a distance of 37 chains towards Starling 



