Speight. — The Tertiary Beds of the Trelissick Basin. 



325 



whereas Hutton correlated what McKay calls the Ototara limestone with 

 the Amuri limestone ; (3) following on from this, McKay correlated the 

 upper limestone of Hutton with the Mount Brown limestone, whereas the 

 latter associated it with the Weka Pass stone ; (4) they both put uncon- 

 formities above the lower limestone, but on different evidence. 



The present author considers that there is strong evidence of physical 

 conformitv in the whole sequence, and that there are not two limestones 

 but only one, which is divided apparently in some parts of the district into 

 two parts bv ash beds from contemporaneous volcanoes. 



2. Sequence, Thickness, and Arrangement of Beds in Particular 



Areas. 



(a.) Lower Members of the Tertiary Sequence. 



The part of the district where the lower members of the sequence can 

 be studied best lies on the east side of the basin. Here the Broken River 

 and its large tributary on the south, the Porter River, cut across the strike 



Fig. 2. — Section along Broken River. Distance, about 4 miles. Direction, W.N.W.- 



E.S.E. 1, greywacke ; 2a, sands, greensands ; 2b, marls, &c. ; 3, tuff 



beds; 4. limestone; 5, sands, sandy clays, shales, and conglomerates — 

 Pareora beds. 



of the beds, and good sections are to be observed on the high banks of 

 the rivers. We get in the Porter River and in the Broken River below the 

 junction the following sequence, in descending order, underneath the lime- 

 stone (fig. 2) :— 



Volcanic tuffs and calcareous tuffs 



Marl .. 



White quartz sand 



Concretionary calcareous sand 



White quartz sand 



Concretionary band 



White quartz sand 



Marl .. 



White quartz sand 



Marl .. 



White quartz sand 



Marl 



Concretionary greensand . . 



Sands, &c. including the oyster and shell bed 



Sulphur sands, white quartz sands, sands with im- 

 pure lignite, light greensands, sandy clay, and 

 Avhite sands, following in that order 



Greywacke. 



The beds strike N. 30° W., and dip S. 60° W. at angles approximately 

 15° above the junction of the two rivers, but which become slightly steeper 

 on tracing the beds east. Throughout the series of beds enumerated above 

 there is no sign of unconformity, as has been admitted by all who have 



70 ft, 



150 ft. 



8 ft. 



2 ft. 

 20 ft. 



6 in. 



12 ft. 



4 ft. 



3 ft, 

 28 ft. 

 50 ft, 



100 ft, 

 500 ft. 

 800 ft. 



300 ft. 



