49

a—9.

showed to the junction of the two main branches of the stream. Below this to the beach the channel of the creek has been excavated in slates. In the right-hand branch of the creek it is said limestones and beds or concretions full of large oysters occur, but this was not explored. A black oyster of lesser size than that seen on the coast-line was met with between the limestone and the coal in the left branch. The coal-seam on the track between Coromandel and Cabbage Bay is an outcrop of beds similar to those forming the lower part of the section on the coast at Torihine. In the tunnel on the north-east side of the spur on which the outcrop of coal is situated, the shales and sandy beds covering the coal have been driven on till the conglomerates were reached, but without passing through more than 1 in. or 2 in. of coal. The inclined shaft in the south-west side of the spur was full of water, and partly had fallen in when the place was examined in 1883; yet, where the outcrop was first laid bare was to be seen enough to show that but a few feet of the rocks really belong to the coal-bearing series, and that lower down the spur the rocks are decidedly unconformable, they being slate belonging to the Maitai series, while those forming the plateau top and the higher part of the range are, without doubt, unconformable also. Last year I was shown some fossils, collected by Mr. Jamison, of Cabbage Bay, from the sandy beds overlying the coal at this place, strictly from material excavated in exploring for coal. Among these were a coral, Flabelluna, and a small shell resembling Cardium, which shows clearly that the cover of the coal here, as at Torihine and in Tawhetarangi Creek, consists, at no distance overlying the coal, of marine beds. The conglomerates, coal, and immediately overlying beds belonging to this series, as developed in the Cabbage Bay district, might very well be of local origin, and the deposits of a restricted area. This also might be said of some parts of the limestones, but the foraminiferal limestones clearly indicate ocean conditions, and a wide-spread deposit similar to that which characterizes the Amuri and Cobden limestones in the South Island and over larger parts of the North Island. It must therefore be assumed that these limestones covered the whole area of what is now Cape Colville Peninsula, and that by denudation they and the associated beds have been removed from every part accessible to examination prior to the deposit of the next succeeding rocks, whether sedimentary or volcanic. Thus, as a result of long continued errosion, the physical features of the peninsular district must have been remodelled, and, assuming that the beginning of the display of volcanic energy, which has left such abundant evidences of its action, was subsequent and not prior to the deposit of the coal-bearing Cretaceo-tertiary series, it can be made apparent that the configuration of the country was hilly in the main and sometimes mountainous. This is not inferred from the heights to which the older rocks rise at the present time, for the country has been unequally elevated and depressed during Tertiary times, but from the irregularities of the surface viewed as a sloping plain, dipping towards the east or south-east. Sections taken from Cabbage Bay, east or south-east, will show this. Also, the same will be apparent in any line of section taken from the vicinity of Coromandel towards Kennedy Bay or Whangapoua, or from Manaia to Kuaotunu. Nor would the evidence be less decisive on any traverse from the coast-line south of Manaia to the main range south of the Tiki and Castle Rock Ranges. Whether, then, it be assumed that the Cretaceo-tertiary beds are older or younger than the Thames-Tokatea group of volcanic rocks, it is certain that the products of volcanic action were at the first on an irregular hilly or sub-mountainous surface. The probabilities are great—nay, it is almost a certainty —that the coal-bearing series is older than the first formed of the volcanic rocks, and, assuming the correctness of this conclusion, it follows that the Thames-Tokatea volcanic rocks must be considerably younger than the youngest of the Cretaceo-tertiary series. These considerations will scarcely admit of the coal-bearing series being regarded as younger than of the Cretaceous period. Volcanic Formations. The great feature of the Cape Colville Peninsula at the present time is a vast accumulation of volcanic matter, that, from the northern extremity to where the land ceases to be peninsular, gives to the entire district its peculiar character. This is piled up in mountain masses, and gives to the greater part of the Peninsula the rugged character that distinguishes it. The physical features of the present day are, however, the result of sub-aerial denudation after the last of the four great groups of volcanic rocks had been errupted. There were periods of denudation and of sedimentary deposit between each of the great divisions of volcanic rocks ; and before the commencement of each succeeding display of volcanic energy the surface of the older deposits had been greatly modified. Unconformities are therefore to be traced, some of which are well marked locally. In other cases decisive evidence is not to be obtained, but the general arrangement of the rocks if considered carefully in detail, points to the fact that the older group had to a large extent been denuded before the commencement of the succeeding outburst. Previous writers on the geology of the Cape Colville Peninsula have generally considered that the volcanic rocks of the district belonged to two, and in some cases three, distinct periods of time. As, for instance, the rocks of the Thames and Coromandel Goldfields, and the younger series known as the trachytic breccias of Beeson's Island. The rhyolitic rocks of the south-eastern part of the district are mentioned both by Hector and Cox, and latterly by Park, but no one clearly defines the position of these in relation to the other rocks of the Cape Colville Peninsula. Sometimes these latter are regarded as the equivalents and an extension northward of the trachytic and rhyolitic rocks of Rotorua and the interior central parts of the North Island, but no one has investigated their relations to the rocks of the Beeson's Island group. Thames-Tokatea Group. The rocks of this group are in the main fine-grained tufas, ash, or breccia beds consolidated to form the "sandstone" of the gold miner. At many places there are interstratified floes and intrusive 7—C. 9.