166 Transactions. 



Under the microscope the greensand is seen to be made up of grains of 

 glauconite and calcite, with occasional crystals of quartz. The glauconite- 

 grains, which are the most abundant, are rounded, and up to 0-2 mm. in 

 diameter. The Dominion Analyst supplies the following partial analysis 

 of the greensand : Potash (K 2 0), 2-72 per cent. ; phosphorus pentoxide 

 (P 2 5 ), 4-32 per cent. ; calcium carbonate (CaC0 3 ), 39-87 per cent. 

 Considering the amount of glauconite present, the percentage of potash is 

 low. The only other analysis of New Zealand greensand the writer can 

 find is that of a sample from Iron Creek, Broken River, Canterbury (52nd 

 Ann. Rep. Dom. Lab., p. 28), which also contains a low percentage of 

 potash — namely, 1-35 per cent. 



After the deposition of the marl, elevation caused its erosion, as is shown 

 by the presence of pieces of the marl in the greensand. The bands of 

 phosphatic nodules point to elevation to allow some of the glauconite to be 

 washed away and the concretions concentrated into layers. 



Caversham Sandstone. 



The Caversham sandstone outcrops about 25 chains to the east of the 

 Burnside marl-pit, whence it extends to Burnside and Caversham beyond the 

 area mapped. The rock which is exposed near the Burnside pit is a compact 

 calcareous sandstone. Outside the area the formation is fully 300 ft. thick. 



Fauna and Age of the Beds above the Piripauan. 



Mr. P. G. Morgan, after inspecting the fossils obtained by McKay from 

 the glauconitic mudstone, informed the writer that the collection as a 

 whole is unlike any from Oamaru. Mr. J. Marwick, of the Geological 

 Survey, who examined the same collection, reports that the specimens, 

 with the exception of a Dentalium. which is nearest D. pareorense Pilsbrv 

 and Sharp, are casts for the most part indeterminable, and comments in 

 the same manner as Mr. Morgan . 



The fauna comes from the base of the bed. Odontaspis elegans Agassiz 

 occurs in the mudstone at Abbotsford Station. The cemented greensand 

 at the top of the glauconitic mudstone yielded Dentalium solidium Hutton 

 and a leaf which resembles the dicotyledon Daphnophyllum australe von 

 Ettingshausen (1891, p. 275). 



The marl of the Burnside pit contained the following teeth : Isurus 

 retroflexus Agassiz, Notedanus marginales Davis, Odontaspis elegans Agassiz, 

 and 0. attenuata Davis. 



The Geological Survey forwarded a collection of Foraminifera from 

 the Burnside pit to Mr. F. Chapman, of Melbourne, who determined the 

 following* : Haplophragmium latidorsatum Born, H. emaciatum Brady, 

 Cyclammina incisa Stache, Gaudryina reussi Stache, G. pupoides d'Orb., 

 Nodosaria radicula (L.), A T . raphana (L.), Margimdina asprocostulata Stache, 

 Cristellaria rotulata (Lam.), Truncatulina ungeriana (d'Orb.), and Rotalia 

 soldanii var. nitida Reuss. Commenting on their age, Chapman states : 

 ' In regard to the Foraminifera of the Burnside marls, they show some 

 affinity with the fauna described by Stache (Whaingaroa), and also with 

 our [Victorian] Balcombian beds. They are therefore low in the series." 



The following is a list of fossils from the Caversham sandstone taken from 

 Hutton (1875, pp. 51-52) and given modern names: Atrina distans (Hutt.), 

 Amusium zitteli (Hutt.), Cueullaea attenuata Hutt., ■fFidgoraria arabica 

 Hutt. (Mart.), Galeodea senex (Hutt.), fGlycymeris laticostata (Q. & G.), 



* Communication to Mr. P. G. Morgan, received September, 1920. 

 t Still living. 



