Recent. 

 Pliocene. 

 Lower Tertiary. 

 Lower Tertiary. 



450 Transactions. 



easterly direction on the north boundary of the district, reaching 

 the plain opposite Cemetery Hill. Between this spur and the 

 former one the hills descend somewhat more abruptly to the 

 plain. In the neighbourhood of the gorge a small cross-spur 

 runs northward parallel to the road ; the western flank of this 

 spur was the site of the original discovery of rock-phosphate, 

 and is now the scene of the greatest activity in the quarrying 

 of the rock. 



Formations of the District. 

 7. Rock-phosphate . . Secondary origin . . Recent, 

 6. Sandstone . . Secondary origin 



5. Alluvium 



4. Basalt . . Oamaru formation 



3. Calcareous series . . Oamaru formation 

 2. Grits and con- 

 glomerates . . . . • • Lower Tertiary. 

 1. Foliated schist . . Kakanui formation . . Silurian (or older). 



Summary. — The basement rock of the district consists of 

 the foliated mica-schist which constitutes the greater part of 

 the Province of Otago. On this basement thin patches of grit 

 and conglomerate are irregularly distributed. Above these 

 come glauconite sands, which gradually merge upwards into 

 the limestone as they become less and less glauconitic. Above 

 the limestone, which lies practically horizontal, there occur 

 in various places a brown sandstone and patches of rock- 

 phosphate, usually occurring together ; their outcrops roughly 

 follow the contour-lines, but rise towards the north-west along 

 with the limestone. In many places the limestone is absent, 

 the rock-phosphate then resting directly on the glauconite 

 sands. The sandstone and the rock-phosphate are confined to 

 the outer margin of the limestone, and do not extend beneath 

 the basalt-flow which caps the western hills and forms occasional 

 outliers on the hills of the eastern side. The low-lying portions 

 of the schist are covered by the alluvium of the Taieri and the 

 Tokomairiro Plains. 



Schists. 



Character of the Schist. — This rock may be properly termed 

 a " chloritoid mica-schist."* In the hand-specimen muscovite 

 is clearly seen along the foliation planes, but under the micro- 

 scope it is scarcely apparent, the rock being then seen to con- 

 sist mainly of alternating folia of chlorite and quartz. The 

 quartz often surrounds fibrous masses of chlorite, which are 

 elongated in a direction parallel to the plane of foliation. Rutile 



* Rosenbusch, " Elemente der Gesteinlehrc," p. 517. 



