Marshall. — Cainozoic Fossils from Oamaru. 



38 J 



In the floor of the Awahokomo Valley, about three miles from the point 

 where it joins the Waitaki, the junction of the Tertiary strata with the 

 Maitai rocks of which the Kakanni Mountains are formed is to be clearly 

 seen. The actual plane of junction dips 73° to the south, and strikes 15° 

 west of north. The Maitai rocks to the south of the plane of junction are 

 greatly shattered. This is best seen when the line is followed over the hills 

 which lie to the north of the Awahokomo. The weathering of the rocks 

 has here developed their shattered nature, and they break down into a clayey 

 material, which still contains angular fragments of rock. This shattered 

 material has been called by McKay " glacier deposits."' * 



There can be no doubt that this plane of junction is a thrust-plane, 

 though more highly inclined than is usual for such planes. This high in- 

 clination of a thrust-plane appears to be a feature of those examples that 

 have been described in New Zealand. f 



In the present case the great tectonic movement has had relatively little 

 effect on the Cainozoic sediments over which the Maitai rocks have been 

 thrust. These are in no way crushed, and the fossils which are contained 

 in them are not distorted. This again appears to be a feature of New Zea- 

 land Teitiaries when they are involved in tectonic movements. The fossils 

 in the narrow band of Tertiary rocks, only 15 ft. wide, at Stony Creek, near 

 Lake Wakatipu, with schist on both sides of it. are not distorted, and again 

 the rock is not crushed. In the Clarence Valley the rocks are not fossiliferous, 

 but their structure does not appear to have suffered in any way by the great 

 tectonic movements which have been so well described by Cotton. 



On the northern bank of the river the beds soon rise gradually, and before 

 long the basal quartz gravels with coal-seams are exposed. They contain 

 good specimens of fossil wood similar to that described by Unger as Nicolia.J 



S.W 



Fro. 2. — Section across Wharekuri Basin 



• way from the river the ground rises somewhat more steeply, and highly 

 siliceous greensands are seen to rest on the quartz gravels. These greensands 

 contain Cucullaea, Venericardia. Dentalium, and Natica rather badly pre- 

 served, but apparently similar to the species that were found in the river- 

 bank. In the Awahokomo Valley the same genera were found in a greensand 

 lying only 20 ft. above the quartz gravels, which there contain coal-seams. 

 There is obviously every reason to believe that the whole of the younger 

 rocks in the Wharekuri Basin belong to the same series. 



On the north-east side of this basin of Tertiary rocks the Maitai sediments 

 rise abruptly in a steep scarp for about 1,000 ft., and this scarp is but little 

 incised by the erosion of the streams that flow down it. The outcrop is 

 separated from that of the Tertiary rocks by a distance of about 30 ft. only, 



* Rep. N.Z. Geol. Surv., 1881, p. 60. 

 t Cotton, Geogr. Mag., 1913, p. 227. 

 $ " Reise der ' Novara,' " 1865 Geologischer Theil, Bm<l 1 p. 1 3 



