Grange. — Geology of Green Island Coalfield. 165 



The glauconitic mudstone outcropping on the bank of Abbott's Creek 

 near its junction with Waterfall Creek contains septarian nodules. The 

 boulders are perfectly spherical to the eye. and are about 4 ft. in diameter. 

 They resemble the well-known Moeraki boulders. 



An inspection of the contact of the glauconitic mudstone with the under- 

 lying beds shows it to be disconformable. The shelly limestone, taken as 

 a whole, has a fairly even surface, but in places an irregular contact has been 

 observed. At the point marked x on the map, 13 chains north-east of 

 the Brighton sand-pit, a glauconitic sandstone lies fully 5 ft. below the level 

 of the limestone at 10ft. on either side; and 4 chains east of this junction 

 a quartz sand, consisting at its base principally of clay, rests on an irregular 

 surface of the Cretaceous strata. The sand grades into a glauconitic sand- 

 stone, which higher up is replaced by a glauconitic mudstone. At Green 

 Island, in exposures at the Jubilee sand-pit and 30 chains to the north-west 

 of Fernhill sand-pit, the sandy base of the glauconitic mudstone contains 

 quartz pebbles up to \ in. in diameter, and a lens of rock of the nature of a 

 aceensand, 30 ft. long and 2 ft. thick, containing quartz pebbles, occurs in 

 ,^he upper part of the quartz sand in the Jubilee pit. Gray's pit shows 

 a similar body, but it is not accessible. Since glauconite is not likely to 

 form where pebbles \ in. in diameter are deposited, the lower portion of 

 the glauconitic mudstone has most probably been rewashed. The evidence 

 indicates a small erosion interval. 



Sandstone. 



Sandstone beds stretch from the source of Waterfall Creek to Abbott's 

 Creek, round the lower slopes of Kaikorai Hill, and down to Green Island 

 Station. In many places they are exposed in cliffs owing to slipping. The 

 sandstone, which varies from 170 ft. to 200 ft. in thickness, rests conform- 

 ably on the underlying beds. It is composed of quartz-grains and scales 

 of muscovite, slightly compacted. An excavation made close to one of a 

 line of springs marking the junction of sandstone and mudstone, near 

 Samson's house, showed a sand made up of well-rounded quartz-grains, 

 similar to that occurring above the coal-measures. 



Marl. 

 The marl occupies a strip from the southern slope of Kaikorai Hill to 

 the railway -line near Green Island Station. It attains a thickness of 170 ft., 

 and has a dip of 1 in 8 40° south of east. The mud has a light-blue 

 colour when freshly exposed, but weathering soon produces a cream tint. 

 The lower part of the bed is somewhat sandy, and contains glauconite. 

 Pyritic concretions occur in the Burnside pit. 



Greens and. 



A greensand 2 ft. thick rests on the marl at the Burnside pit. About 

 15 chains to the south-east, in the Kaikorai Stream, a more accessible outcrop 

 of the bed is visible. Here the base of the greensand, which is 6 ft. thick, 

 contains flakes and small pieces of marl up to 1 in. in greatest diameter. 

 Some 9 in. above the contact in a layer 2 in. thick of phosphatic nodules, 

 succeeded 10 in. above by another band with a similar thickness. The 

 nodules appear to be quite similar to those dredged by the " Challenger " 

 Expedition (Deep Sea Deposits, p. 396) south of the Cape of Good Hope. 

 An analysis of a nodule by the Dominion Analyst showed it to contain : 

 Insoluble in acid, 16-68 per cent. ; lime (CaO), 38-38 per cent. ; carbonic 

 anhydride (C0 2 ), 12-55 per cent. ; water and organic matter, 3-83 per cent. 



