liockii near Hcathcote. 323 



but the bedded fragments are umre completely replaced than the 

 others, and scmie approach in character the black cherts. Secon- 

 dary quartz as -well as chalcedony occurs, and it is probable that 

 all the silicification was effected after the formation of the con- 

 glomerate. In one fratrment a circular cross-section in chalce- 

 dony may represent a section of an organism. From the appear- 

 ance of the rock under the microscope, it may be either a local 

 shoreline detrital conglomerate, or a rather coarse submarine 

 tuff. In any case it is clearly interbedded, and cannot be re- 

 garded as representing a stratigraphical break between two 

 separate formations. 



The relations of the Dinesus Beds to the Diabase have not 

 been clearly seen. The diabase for at any rate some distance 

 along its outcrop east of the Dinesus Beds is either the platy type 

 as occurs at Red Hill, or the highly silioified jasperoid, and I 

 have not anywhere seen an exposure showing the relation of the 

 two series. The abi-iipt junction shown on the Quarter Sheet 

 between the two at the S. end of the Dinesi/s Beds I have been 

 unable to confirm. Cherty tuff-like rock fragments occur in the 

 paddock both to the N. and S. of the junction, as mapped, but 

 no exposures are seen. Th.e field and microscopic evidence would 

 admit of two explanations. On the one hand the diabase may 

 be an older series and the Dinesus beds may represent bedded 

 detrital rocks from the old diabase land area. On the other 

 hand, the diabase may be practically contemporaneous and 

 represent submarine lavas and tuffs passing Avestward into more 

 finely-bedded tuffs, the Dinesus series. 



7. — Nature and Origin of the Igneous Rocks. 



The Basic hjntoua .Series. — As 'pointed out by previous 

 workers, the basic igneous rocks comprise intrusive masses, lava 

 flows, and fragmental (pyroclastic rocks). 



Dr. Howitt and Professor Gregory maintain that most of the 

 rocks are intrusive, while Mr. Dunn, from field evidence, regarded 

 them as mainly surface rooks. Within the limits of the area 

 I have observed — viz., from Photograph Knob on the south, to 

 Lady's Pass on the north — I find both field evidence and micro- 

 scopic evidence in support of the view that the bulk of the 

 rocks consist of lavas, tuffs and agglomerates, and that intrusive 



