Pabk. — On the Jurassic Age. of the Maitai Series. 431 



Art. XXXIII. — On tJie Jurassic Age of the Maitai Series. 



By Professor James Park, F.G.S., Director Otago Univer- 

 sity School of Mines. 

 [Read before the Otago Institute, 9th June, 1903.] 

 Plates XXXIII. and XXXIV. 

 EocKS belonging to this formation are widely distributed in 

 New Zealand, and play an important part in the structure of 

 the mountain-ranges in both Islands. In the neighbourhood 

 of Nelson, where they are typically developed, they consist of 

 a great assemblage of greenish-grey sandstones, blue, green, 

 red, and grey slaty shales, and limestones, with a few subordi- 

 nate beds of red and green slaty breccia. The blue or green 

 shales often alternate with thin laminae of grey shale or sand- 

 stone. 



The average general bearing is N. 20° E. (true bearing). 

 The arrangement of the strata is displayed to great advantage 

 in the valleys of the Matai, Brook Street, and Eoding Streams, 

 which descend from the Dun Mountain region at nearly right 

 angles to the trend of the series. The beds are seen in all 

 three lines of section to be arranged in a great synclinal fold. 



The strata on the western side of the syncline — that is, 

 immediately behind the Town of Nelson — are associated witii 

 massive sheets and numerous ramifying dykes of a chloritic 

 basalt, "'^ and on the eastern side by a remakable development 

 of altered ultra-basic rocks, principally peridotite and serpen- 

 tine, the latter often traversed by veins of bronzite, hyper- 

 sthene, and other pyroxenes. 



The eruption of these igneous rocks was probably con- 

 temporary with, or at least not much later than, the deposi- 

 tion of the beds with which they were associated. 



Age of Maitai Sekies. 



The late Dr. Von Hochstetter, who examined these rocks 

 in 1859, referred them to the Lower Trias, t placing them 

 conformably under his Richmond sandstone, the equivalent of 

 the Wairoa series of Sir James Hector. He described them 

 as containing no fossils, and apparently ascribed them to the 

 Triassic period, from their association with the Eichmond 

 sandstone, in which he found Monotis salinaria var. rich- 

 mondiana, Zittel, a typical Trias form in Europe. 



Sir James Hector, in the Catalogue of the Colonial 

 Museum, 1870, in his " Synopsis of the Arrangement of the 

 Eormations represented by the Collections of Fossils," also 



* Huttoii, Proc. Boy. Soc. N.S.W., 1889, p. 152. 

 t Hochstetter's "New Zealand," 1867, page 57. 



