Cotton. — The Tuamarina Valley. 



317 



Geological Structure. 



Various autliors* liave recorded their observations of the geology in the 

 neighbourhood of Tuamarina. 



A bricif g.sneral statement will here suffice. The Sounds district is com- 

 posod almost entirely of sandstone or greywacke and schists, all much de- 

 form, d. Practically nothing is known of the structure, but it is certainly 

 compKiX.t 



According to McKay, J the boundary between the sandstone (his Upper 

 Devonian) aud schist (his ? Silurian) coincides very nearly with the line 

 of the Tuamarina Valley. He regards it as probable that the junction is 

 the iue of a fault,§ and it is certainly true that at the low saddle, men- 

 tioned above between the Tuamarina Valley and the stream at the head 

 of Pictou Bay, there is present a small outlier of Tertiary mudstone which 

 probably owos its preservation to its having been faulted in. 





■-"t- '' '?'^^^S?I'S5^^^;^ 



j^^^V^S?^^ 



Fig. 2. — The Low Saddle (250 ft.) between the Tuamarina Valley and the 

 Stream flowing into Picton Bay. 



Elevation Railway-station is on the saddle, and the railway to Blenheim passes 

 around to the left. View looking north-east. 



The low pass, an unu ual feature (see fig. 2), is accounted for by the pre- 

 sence of the weak mudstone, and it is possible that the position of the valley 

 is determined by the fault, but it is by no means certain that a fault exists 

 for the full length of the valley. Nor is it at all necessary to assume its 

 existence in ordur to account for the position of the valley, for other parallel 

 valleys are present. It i . possible that the drainage-lines are determined 

 by systems of master joints, if not by bedding. 



* See especially Hochstetter, F. von., " Geology of New Zealand " (Auckland, 1864), 

 p. 93, and atlas, map 6 ; Hutton. F. W., " Report on the North-east Porti.m of the South 

 Island," Rep. Ge. 1. Expl., 1873-74 (Wellington, 1877), p. 31 ; Hector, J., Progress 

 Report in Rep. Geol. Expl., 1873-74 (Wellington, 1877), p. ix ; McKay, A., " The District 

 between the Kaituna Valley and Queen Charlotte Sound," Rep. Geol. Expl., 1878-79 

 (Wellington. 1879) pp. 86-97; McKay, A., "On the Geology of Marlborough and the 

 Amuri District of Nelson," Rep. Geol. Expl., 1888-89 (Wellington, 1890), pp. 85-185 

 and map opp. p. 96. 



fSee McKay, loc. cit. (1879), p. 89. 



X Loc. cit. (1890), map opp. p. 96. 



^Loc. cit. (1890), p. 103. 



