part 3] THE TRIAS or jS'EW Zealand. 175 



Ti-ias on the north-west. The strip of Kaihikn Beds is half a mile 

 long and a quarter of a mile wide, and the strata dip south-south- 

 eastwards at 55° to 65°. 



In the Wairoa Gorge the Mytilus-'prohlematicus Bed occurs 

 near the entrance, and again on the east close to the Maitai Lime- 

 stone. The intervening space is occupied by the higher beds of 

 the Carnic. 



In the hills south of the gorge the Pseiidomonotis-riclimoncUana 

 Beds occur in full thickness, but are not seen in the gorge itself. 

 At Grarden Gully, about a mile south-west of the Wairoa Gorge, I 

 found a bed of fine-grained greywacke containing many varieties 

 of the Asiatic Noric fossil Fseudomonotis ocliotica. It seems to 

 occupy the limb of a syncline, possibly a faulted syncline, and 

 I believe the Noric Pseiidomonotis-ocliotica Beds to be the highest 

 that occur in the Nelson area. 



No Jurassic fossils have been found in this part of the South 

 Island. All the evidence that I saw led me to conclude, in opposition 

 to recent Survey results,^ that there is a series of strike-faults 

 parallel to the structural axis and that the Trias is partly overthrust 

 to the north-west by the Maitai Series. The Tertiary deposits of 

 the Waimea Plains, which bound the Trias on the north-west^ 

 are tilted up along their junction, and are probably overthrust to 

 some extent in their turn by the Trias. 



Okuku (Ashley County). 



The geology of this very mountainous district is little known. 

 McKay studied and described it in 1879, ^ and states that the 

 whole of the northern end of the Mount-Torlesse range is occupied 

 by Trias and younger formations, which form the higher peaks of 

 Mount Torlesse. The rocks consist of a great thickness of con- 

 glomerates, sandstones, red and green so-called ' diabasic ash ' (by 

 which one may probably understand coarse greywacke), and lime- 

 stones. JMijtilus prohlemaficits and Monotis salinaria are said to 

 occur in the limestones and in the ' diabasic ash.' These fossils 

 are found in immense numbers in the UjDper Okuku Valley, in a 

 limestone associated with cherts. I had no opportunity of visiting 

 this locality, and McKay's report is not quite clear as to whether 

 the Monotis and 3Lffilus occur together or in separate strata. I 

 examined a series of the 3Ionofis-Y\k<d shells in the limestone from 

 this district belonging to the New Zealand Geological Survey, and 

 selected several examples to be sent to England. These pieces of 

 limestone contain Monotis, but no Mytilus. I could find no trace 

 of the anterior byssal notch characteristic of JPseudomonotis in 

 any of these shells, and therefore am compelled to regard them 

 as really the Alpine Monotis salinaria. If this be the case, their 

 reported association with Mi/tilus prohlematicus may be explicable, 

 as Monotis salinaria is recorded from Carnic horizons in Europe. 

 Perhaps future research in the district may clear up these points. 



1 Bibliography, 22, pp. 20-22. - Bibliography, 29. 



