Reference to Literature.
Davis, W. M., 1928. The Coral Reef Problem, pp. 151-4.
Haast, Julius von, 1879. Geology of Canterbury and Westland, pp. 399-401.
Jobberns, Geo., 1928. The Raised Beaches of the North-East Coast of the South Island of New Zealand, Trans. N.Z. Inst., vol. 59, pt. 3, pp. 508-570.
Marshall, P., 1929. Beach Gravels and Sands, Trans. N.Z. Inst., vol. 60, pt. 2, pp. 324-365.
Speight, R., 1908. Terrace Development in the Valleys of the Canterbury Rivers, Trans. N.Z. Inst., vol. 40, pp. 16-43.
—— 1911. Preliminary Account of the Geological Features of the Christchurch Artesian Area, Trans. N.Z. Inst., vol. 43, pp. 420-436.
—— 1917. Geology of Banks Peninsula, Trans. N.Z. Inst., vol. 49, pp. 365-392.
Note.—Since writing the above, Mr. Jobberns has drawn my attention to the existence of greywacke pebbles on the top of a stack on the east side of the outlet of Lake Forsyth. I have examined the spot and also the cliffs in its vicinity, and find that the stack and cliffs are covered with a deposit of typical loess and the pebbles either rest on this or in some few cases are perhaps included in it. The latter cannot be demonstrated for certain, but clear-cut banks of loess show no included pebbles and the few that are apparently included may have been washed down from above and been caught in loess material which has also slumped, thus giving the impression that they are included. The pebbles are of the ordinary beach type of the neighbourhood, and are exclusively of greywacke, quartz, and jasperoid rock. They range in size from three inches downward, but the pebbles at higher levels are usually small. The number is greatest at the lower levels and none occur higher than 200 feet above sea-level. There are at last two Maori ovens with burnt stones in the area looked at.
Now it might, at first sight, be assumed that these pebbles represent an old beach, and that the land was at one time ast least 200 feet lower in level, but there are objections to this conclusion. First of all, there is no definite deposit showing the structure of a beach, nor
is there any eroded shore platform on which it might rest. If this had been the case, the pebbles should have been formed of the country rock, a basalt or basic andesite, and although pieces of this do occur they are not beach-worn at all. There is also the objection, that had the land been 200 feet lower, then all the present spit would have been submerged to a depth of at least 25-30 fathoms, and the sea would have extended over a wide belt of plain to the west. It would then have been impossible for greywacke pebbles of the beach type to have been transported across such a belt of sea, at least 25 miles wide, in the numbers that actually occur, as taking into account their only possible source they must have been. The pebbles should have been of Banks Peninsula origin had they been a beach deposit. On the end of the spur terminating in the Devil's Knob there is a capping of loess, and in this at a height of nearly 300 feet are very small quartz and jasperoid pebbles, never more than an inch in diameter and in very small numbers. These might conceivably have been blown to the position where they occur, or they may have been derived from the heaps of moa gizzard stones, which they most closely resemble, the remains of moa bones being also a characteristic content of the loess. If there had been any definite beach on the hills close to Lake Forsyth, similar deposits should occur on the hills to the west, and all I can find are occasional small pebbles either on or in the loess. The ends of these spurs also show signs of having been occupied by the Maoris as ovens occur frequently. Further west still they are increasingly scarce and finally do not appear at all. So I must conclude that they were not deposited in that situation by the sea, but carried there by adventitious means. All the same I am not prepared to say what this is, except that it is conceivable that heavy seas may have been responsible for some of them near the present coastline, wind for some of the smaller ones; and also, since these spurs were formerly inhabited, that they may have been carried to their present position by man himself.†
If they have been deposited in the position where they now lie by the sea, and some of them are really included in the loess, then it again opens the question as to whether the loess is a silt deposit, as maintained by Hutton, or a land deposit as maintained by most other authorities, including Haast and Heim.