Gkange. — Geology of Green Island Coalfield. 



157 



Art. XVIII. — An Account of the Geology of Green Island Coalfield. 



By L. I. Grange, M.Sc, A.O.S.M. 

 Communicated by J. Henderson, M.A. ; D.Sc., B.Sc. in Eng. (Metall.). 



[Read before the Wellington Philosojrfiical Society, 13th October, 1920 ; received by Editor, 

 31st December, 1920 ; issued separately, 4th July, 1921.] 



INTRODUCTION. 



The area described is the Green Island coalfield, which, lies at its nearest 

 point four miles south-west from Dunedin. The Kaikorai Stream forms 

 the southern boundary from the Burnside marl-pit to the sea, whence the 

 border follows the coast to Brighton Creamery. A line due north from 

 the marl-pit to Abbott's Hill Road makes the eastern border, the western 

 being formed by a line north from Brighton Creamery to the Chain Hills. 

 The northern boundary is the Chain Hills and Abbott's Hill Road. The 

 area includes Freeman's, Fernhil], Green Island, and Jubilee Collieries, as 

 well as the Brighton Mine. 



To Mr. P. G. Morgan, Director of the Geological Survey, the writer is 

 indebted for allowing Mr. G. E. Harris to draw the accompanying map. 



OUTLINE OF GEOLOGY. 



The oldest rocks of the district are the schists which form the Chain 

 Hills. Overlying the basement rock with great unconformity are the 

 Notocene sedirnentaries. The lowest beds are the coal-measures and quartz 

 sands which outcrop in Fernhill and Christie's Creeks, and at Brighton ; 

 at the last-mentioned locality a shelly limestone overlies the terrestrial beds. 

 Resting with disconformity on the cmartz sand or shelly limestone, and 

 comprising the greater part of the area mapped, is a series of marine beds 

 of which the upward succession is glauconitic mudstone, sandstone, marl, 

 greensand, and Caversham sandstone. There is evidence of a local uncon- 

 formity between the marl and greensand. All the Notocene sedimentary 



