434 Transactions. — Geology. 



We have already seen that Captain Hutton, in his report 

 on the north-east portion of South Island in 1873, placed the 

 Maitai formation above the Wairoa series, classifying the 

 former as Jurassic and the latter as Triassic. 



In his Progress Eeport for the year 1873 the Director of 

 the Geological Survey states that, after an examinaton of the 

 sections relied on by Captain Hutton, he had arrived at the 

 conclusion that the relative positions of these formations as 

 reported by Captain Hutton must be reversed, "as the section 

 up the gorge of the Wairoa Kiver shows the latter " [Wairoa] 

 "formation, with its characteristic fossils (Monotis salinaria 

 and Mytilus 'prohleviaticus) , to rest unconformably on the 

 ' Maitai ' formation.'"'' Unfortunately, he omitted to furnish 

 details of the section showing this unconformity, and in the 

 absence of specific data it is impossible to review the evidence 

 on which he based his conclusion. 



In his reports of 1877 and 1878 Mr. McKay adheres to the 

 classification of Dr. Hector. He examined the typical sec- 

 tions exposed in the Maitai Valley, Brook Street Valley, 

 Eoding Elver, Wairoa Gorge, Sellen's, and Eighty -eight 

 Valley, and, although in no case do his descriptions possess 

 the elaborate exactness of those of Mr. Davis, I found that 

 his field observations were everywhere carefully noted and 

 faithfully recorded. On the other hand, in his discussion on 

 the relative positions of the Wairoa and Maitai formations 

 his conclusions seem curiously at variance with the recorded 

 facts, while some of his sections are obviously constructed 

 to represent his views rather than the facts observed in the 

 field. 



Proceeding from the Waimea Plain through the Wairca 

 Gorge, and thence along the course of the Eoding Eiver, 

 there is exposed a clear section of the Wairoa and Maitai 

 formations in which the dip is continuously to the east- 

 south-east in one unbroken sequence, at angles generally 

 between 65° and 75°, representing in a distance of a mile 

 and a half a thickness of not less than 7,000 ft. of strata. 

 In this section the Trias beds appear first, and are clearly 

 seen to dip under the Maitai limestone. 



At a point just above the first bend in the Eoding Eiver 

 the beds dip west-north-west at an angle of 75°, and thence, 

 following up the river, tlie whole sequence of tlie Maitai 

 formation is repeated down to the limestone and associated 

 conglomerates, beyond which appear the eruptive rocks of 

 the serpentine belt. This synclinal arrangement of the over- 

 lying Maitai formation is also observed in the Maitai Eiver 

 and Brook Street Valley sections. 



♦ Reps. Geol. Expl., 1873-74, p. ix. 



