378 Transactions. — Geology. 



Nugget Point District, Otago. 



From the promontory on which Nugget Point Lighthouse 

 stands southward to False Island, at the mouth of Catlin's 

 Eiver, in a distance of nearly four miles, there is exposed 

 along the coast-line a thickness of over 18,000 ft. of strata,, 

 forming a continuous succession of beds dipping to the south- 

 west at angles that are always very high. South of Catlin's 

 Eiver the higher beds occur in gently undulating folds, and 

 in this manner pass southward toward Waikawa. 



This great assemblage of beds consists of claystones, 

 sandstones, greywacke, and conglomerates, occurring some- 

 times in thin alternating layers, sometimes in thick beds. 

 Organic remains are not wanting, but are seldom abundant. 

 Plant-remains, generally broken and fragmentary, are scat- 

 tered from the base to the summit, and in the higher beds at 

 Catlin's large masses of silicified driftwood are not uncom- 

 mon. Marine shells occur at wide intervals, but are never 

 plentiful except in a few of the lower zones in Shaw Bay, 

 which is now locally known as Roaring Bay. 



The character of the sediments and contained fossils 

 clearly indicate that fluvio - marine or estuarine conditions 

 prevailed during the deposition of these beds ; and the abund- 

 ance of granite and related rocks in the lower conglomerates 

 tends to show that the area of erosion whose dissection pro- 

 vided the materials lay to the south-west, probably in the 

 direction of Stewart Island. 



The fossils and continuous succession of stratified sedi- 

 ments prove that deposition extended unintern;ptedly from 

 Upper Palaeozoic to Jurassic times. 



The lower beds at the north end of Shaw Bay are intruded 

 by a narrow dyke of porphyrite, and excepting this the whole 

 system is singularly free from evidences of contemporary 

 volcanic activity. 



The rocks exposed on tlie coast-line between Nugget Point 

 and the south head of Shaw Bay, embracing a thickness of 

 nearly 5,000 ft. of strata, belong to the Trias and Upper 

 Falaiozoic periods, and the remaining 13,000 ft., lying between 

 the south head of Shaw Bay and Catlin's River, to the 

 Jurassic. 



In 1873 Mr. McKay reported the existence in this district 

 of a " Productns formation, "'■• and my first object was to lo- 

 cate this formation, with the view of ascertaining its relation 

 to the Trias. I made a careful examination of the so-called 

 Productics beds, and was unable to discover any fossils that 



• 



* Reps. Geol. Expl., 187'2-73, pp. 63-65. 



