Art. VIII.—On the Occurrence of Footprints of a Large Bird, found at Turanganui, Poverty Bay
[Read before the Auckland Institute, 29th May, 1871.]
The slabs, now in this Museum, showing the footprints of a very large bird, were procured just below high-water mark, on the right bank of the Taruheru River at Turanganui, Poverty Bay, about 100 yards from its mouth, just at the angle formed by it with the Waikanae creek. The exact position is denoted in the accompanying sketch map. (Pl. VIII.)
My attention was first called to these footprints nearly five years ago by David Millar, who at that time kept a ferry boat on the river, and lived within a short distance of the spot. The portion of rock on which the impressions were visible at that time was about fourteen feet in length and about five feet
in width. The prints are such as one would imagine were made by one of the smaller species of moa. With a very few exceptions they were all of the same size, viz.:—
|Extreme length from heel to tip of middle toe||7⅞ in.|
|From heel to tip of inner toe||6 in.|
|From heel to tip of outer toe||6 in.|
|Distance between tips of inner and outer toes||7 in.|
|Greatest depth of impressions||1⅝ in.|
The only prints of a different size were those apparently of a young bird, all in one series and at regular intervals, every alternate impression being characterised by a peculiarity in one of the toes, which showed that they had all been made by the same bird. The removal of a portion of the overlying stratum of rock, about six inches thick, brought to view another of these smaller impressions, in the exact position which was indicated by the other members of the series. The greater number of the larger impressions were close together and pointed in various directions, as shown by the cast, which represents a few of them from a spot where they were very numerous. In the case of some of them, however, a connection could be distinctly traced, eight or more impressions following one another at regular intervals; but the stride is so short (barely twenty inches from heel to heel of two consecutive impressions) that the bird must have been walking at a very leisurely pace.
The rock in which these impressions are found is very soft, containing a large proportion of a fine pumiceous sand, and has all the appearance of being a river deposit, the birds having walked over it some little time after the fresh had subsided, when the mud was getting moderately dry. Soon after the impressions were made, a quantity of sand, much coarser than that which enters into the composition of the rock, must have been drifted over it by the wind, filling up all the foot-prints, and covering the whole surface to a moderate depth; the general thickness of the layer, after having been compressed by subsequent deposits, being about five-eighths of an inch. That this must have happened soon after the impressions were made, and before the mud had become quite dry, is indicated by the way in which this coarser sand is imbedded in the bottom of the impressions. It is owing to this layer of comparatively loose sand that the impressions have been so well preserved. Subsequent deposits of silt have taken place, covering that in which the impressions are found to the depth of about two feet. All these deposits are now being gradually worn away by the action of the water and of the weather. Overlying the whole, in the part which the water has not interfered with, is a layer of sand, gravel, shells, and soil, to the depth of four feet.
The question naturally suggests itself, what light do these footprints throw upon the age in which the Moa lived in this island? Moa bones have been
found in great numbers in Poverty Bay, in years gone by, many of the earliest shipments to England having been sent from thence by the Rev. W. Williams, now Bishop of Waiapu, in 1842 and the following years. These bones were found by the natives generally in the river-beds, buried in the deep alluvial deposit which covers the bottom of the valley. None, as far as I know, have been found imbedded in the recent rocks, such as that in which the footprints occur. I have found them myself in the bank of the Kopututea River, about six feet below the surface, and I have also picked up a few on the beach at Turanganui, within a short distance of the spot where the footprints are found, but on the opposite side of the river. Whether these bones and the footprints belong to the same period is a question which it is not easy to determine. The alluvial deposit, in which the bones have been found, covers the whole of the lower portion of the valley, forming a plain of an irregular deltoid shape, the base of the triangle at the coast being about ten miles long, and the apex about eight miles inland. Running through this plain there are two rivers, viz., the Kopututea, which is formed by the confluence of the Waipaoa and the Arai, and occupies a middle position, rather towards the south-west side of the plain; and the Taruheru, which falls into the sea at Turanganui at the north-eastern corner of the bay. The alluvial deposit, averaging about twenty feet in depth, has been brought down mainly by the Waipaoa, the banks of which at the upper part of the plain are thirty or forty feet high. It is very seldom now that this river overflows its banks. The last instance of a flood, by which any noticeable addition was made to the depth of the soil on the plain, was in March, 1853, when the overflowing water found an outlet by running into the Taruheru River, leaving behind it a deposit of several inches of mud. But such an inundation had not been witnessed before by any of the natives then living, and as every year passes it becomes less likely that such a thing will occur again, in consequence of the gradual deepening of the bed of the river. Such inundations, however, must have been very frequent in early times, and as the surface of the plain grew higher and the bed of the river became deeper, they would come to be more and more rare, till, as now, they are almost entirely unknown. The growth of the deposit, therefore, under which the bones were buried, must have been very rapid at the beginning, gradually becoming slower, until at last it may be said to have ceased altogether.
The time that would be required for the depositing of twenty feet of loam by this river, and the circumstances under which the silt at Turanganui has hardened into stone, as well as the time that would be necessary for this process, are matters which I do not venture to decide.
Note.—The accompanying diagrams were made by drawing a straight line by the side of each series of impressions, and taking measurements from it to the heel and tips of the toes of each impression. The intervals between the
consecutive impressions of the larger series, starting from one behind those which are represented in the diagram, were 19½, 20¼, 21¾, 19¼, 20½, 19½, and 19 inches respectively, measured from heel to heel. The intervals in the smaller series were 13½, 12½, 13, and 12¼ inches. (Pl. VIII.)