54 G. T. Trechmann — Age of the 



are of Jurassic age. The l'easons for this were, among others, the 

 apparently conformable dip of the Triassic Mytilus problemalicus 

 beds in the Wairoa Gorge beneath the Maitai Limestone ; the 

 supposed equivalence of the Maitai Limestone with the Kaihiku 

 Beds of Eighty-eight Valley ; and the failure to find fossils in the 

 Maitai Limestone. In 1910, however, Park, 1 after examining the 

 limestone fossils collected by McKay in 1878, returns to the view 

 that the Maitai Limestone is Carboniferous. He still, however, 

 expresses doubts on the Inoceramus question, and says that " a careful 

 search was made for fossils at the place where Inoceramus was said 

 to occur, but without success". Some calcite-filled contraction rents 

 were, however, found in the rocks, and it is suggested that McKay 

 might have mistaken these for fossils. In 1911 a report 2 on the 

 re-survey of the Dun Mountain district of Nelson by J. M. Bell, 

 E. de C. Clarke, and P. Marshall appeared. In this report the 

 whole of the Maitai Series, including its limestones, slates, argillites, 

 and contemporaneous igneous rocks, together with the fossiliferous 

 Trias of the district, including the Kaihiku, Oreti, Wairoa, and 

 Otapiri Beds of the earlier reports, are included together as a con- 

 formable series of Trias-Jura age, and are spoken of as the Maitai 

 Series. The inclusion together of all these beds was due partly to 

 the unfortunate fact that again the surveyoi-s failed to' detect the 

 fossils in the Maitai Limestone previously recorded by McKay, but 

 also because of the deceptive appearance of conformity between the 

 Trias and the Maitai. P. Marshall in 1912 3 repeats his opinion 

 that the rocks from the Dun Mountain to the Waimea Plain are 

 a conformable series, but are sharply folded, and attributes a Trias- 

 Jura age to the whole series. 



In October, 1915, when I was in the Wairoa Gorge in company 

 with Mr. F. Worley of Nelson, we made careful inquiries where 

 "Martin's Saw-mill" formerly stood, as it had disappeared since 

 1878. On returning two days later with Dr. A. Thomson we had 

 the good fortune almost simultaneously to find the fossils at the 

 place indicated. I also found an exposure of the same limestone, on 

 the bank of the Boding Biver, just above the point where it joins 

 the Wairoa Biver, which showed the sections of a fair number of 

 fossils on the water-worn surface of the rock. A fairly large 

 collection was made here by Dr. Thomson and myself, and we 

 obtained a few forms in addition to those found in 1878. 



Two days later I visited, in Mr. Worley's company, the Dun 

 Mountain tramway line, and at Wooded Peak, again following 

 closely the instructions in McKay's z'eport, we found the largo 

 bivalves, exactly as he had described, in the slaty argillites, just 

 west of a limestone band which adjoins the gi'eat serpentine and 

 dunite intrusion of the so-called Mineral Belt. Having found the 

 fossils, I paid special attention to collecting hinges or other portions 



1 Oeology of Neiv Zealand, 1910, p. 50. 



2 Tfis Oeology of the Dun Mountain Subdivision, Nelson, Bulletin No. 12 

 (New Series), 1911, p. 21. 



" Handbuch der regionalen Geologie (Heidelberg) : New Zealand and adjacent 

 islands. English reprint, Heft v, Bd. vii, Abt. i, p. 16. 



