254 Geology of 



the rock approaches not only in character that of the upper beds of 

 that series, hut it is also overlaid in the same manner by the next op 

 Waihao formation both east of the Central Chain, and on the West 

 Coast. The rocks only fill a small corner in this Province, at the 

 head of Lake Wanaka — the Eiver "Wilkin forming the northern 

 and western boundary — but they are extensively developed in the 

 Province of Otago, where they form a large belt about fifty miles 

 broad, stretching in a north-north-east direction across that province 

 to the Otago Peninsula. In this zone, named by Captain Hutton 

 "the Wanaka formation," the richest and most extensive gold- 

 fields in Kew Zealand are situated.* 



The beds of which this formation is composed consist of gneissic, 

 mica, and chlorite schists more or less crystalline. They generally 

 possess less inclination to the horizon than the same beds on the 

 opposite slopes of the Central Eange, their dip on the eastern and 

 northern sides of the Eiver Wilkin being on an average about 55 

 degrees, ranging from south-east to north-east ; and on the western 

 side, about 45 degrees, ranging from south to south-west. They thus 

 form an anticlinal, being surrounded on all three sides by the same 

 series of beds, which I have named the Waihao formation. 



ISTear Lake Wanaka and along the upper course of the Eiver 

 Wilkin, the rocks consist of mica and chlorite schists ; more towards 

 the centre of the anticlinal, of quartzose gneiss and of a very crys- 

 talline mica schist, full of laminae or lentil-shaped grains of quartz, 

 often of considerable size, which cause the rock, when broken verti- 

 cally to the foliation, to show a peculiar face. These laminae of 

 quartz are not uncommon throughout the beds, and always give to the 

 schists an uneven appearance. Some of these mica schists are often 

 much contorted, so as to suggest that they were very much pressed 

 together, when in a soft or pasty state, by the quartzose or gneissic 

 beds of a harder nature, between which they are enclosed. Corruga- 

 tions on a large scale are also observable, having all the appearance 

 of ripple marks, but they might, as Captain Hutton suggests, 

 be explained by considering them due to the effects of expansion by 

 heat on soft rocks under great- vertical pressure, the compression thus 

 produced having been relieved by numerous small corrugations, 

 instead of by fewer and larger contortions — (Hutton and Ulrich's 



• See Geological Map of Otago, in Hutton and Ulrich's Geology of Otago — Dunedin: Millfl, 

 Dick and Co. 1875. 



