The Old Gum Bottom

THE OLD GUM BOTTOM

(By Woodpecker – AKA A.H.Meiklejohn)

Provided by Kerry Moore

Now when seismology is being discussed it would be interesting to follow the old gum bottom which in many places shows signs of seismic action, more or less violent.

To carry on our study, perhaps no more suitable locality could be found than the harbour river gum-flats and bluffs at Whangateau.

In the early days of settlement, there was an uprooted forest thrown West to East half buried in sand on part of the low land known as gumflats. These trees had fallen on and amongst stumps of a previous forest that had been burnt.

The trees of these stumps had grown over and in some cases astride of huge boles seven to eight feet thick.

Now what has been the cause of this uprooting of forest trees, eight, ten or twelve feet thick, that had withstood the most violent gales for centuries, tipped over like ninepins? At the present time the first thought would be cyclone, but a little tell-tale has been left that proves it must have been seismic action.

This industrious little fellow, known to the timber worker as pin-holer, has left his trademark in kauri logs that have been buried for thousands of years, possibly for ages. Some of these logs, taken from gum swamps, are to all intents and purposes the same as green logs that have been cut but a few months, except that the timber turned a dark brown, or, in some cases, black a few minutes after being sawn up. The bark adhered firmly to the log, the sapwood w as quite sound except for a few scattered pinholes. Little nodules and drips of gum on this bark proved the absence of fire.

It is interesting to follow the work of this little pin-holer, some idea can then be formed of how these trees came to be in such a good state of preservation.

Now this little fellow will not attack a healthy green tree, but he will get busy on the first sign of decay or loss of vitality. As an instance, he will start boring a healthy tree a few minutes after felling, or take a tree that has been slightly scorched by fire. He will soon get to work, the bark will crack in places and start to rise; this becomes a breeding home and in a year or two the sapwood is useless.

In the case of these buried trees, the probability would appear to be that slight seismic action caused the low land to become too wet for kauri; it would then gradually die, the pinholer would get working, but soon after more violent action upset the forest and sank it under water. This land has since risen six to eight feet above high water and the process is still going on.

In a bend in the river we find this old gum bottom under twelve feet of hard sand stone, in which the slope of the sea beach and tide ripple can be traced.

Again this gum bottom dips down under Mangrove-covered mud flats, once rich in gum.

On the high land side of the river we find this old gum bottom with stumps and tree trunks edging in under twenty to thirty feet of pure yellow clay, while up more than one narrow creek with high clay banks we find huge trees and trunks crossed and recrossed in every direction, a wealth of timber that may yet be recovered.

We follow this gum bottom, more or less, all over the harbour. In some places it can just be traced on hard cement like sandstone. Yet again it dips down through peat, anything from few inches to perhaps six feet, mostly rich in gum, much broken timber, stumps, or an occasional tree trunk. Logs and stumps are in the channel at thirty feet low water.

No doubt this gum bottom dips under the sand bar and could be found on the open beach, as it is found at Matakana, Pakiri, Mangawai, Waipu, and many other places. How far these vast forests extended out to what is now deep water can never be known.

It is hard to understand how this cement-like sandstone was formed, bearing in mind that well preserved vertical kauri roots and gum are found in, amongst, and under it. In one patch of several acres, the gum had been heated or boiled, like clear glass bubbles, or marble size grains, resembling fire opals.

Where dairy herds graze on rich pastures miles inland, this old gum bottom has been found in wells, sunk twenty to forty feet deep. Near by on the crown of some soft rock promontory, perhaps hundreds of feet above sea level, old fissures have been found filled with gum – gum of an age, however, that corresponds with the oldest taken from the adjoining gumfield.

The kauri has been everywhere on this Northern peninsula, high up on the mountain tops, deep down in the coalmines, out in the ocean depths, a wealth of gum lies buried. Ages on ages of forest growth, periods of mild seismic action, periods of violent seismic action, have left a very mixed state of affairs, which although, puzzling, are interesting.Now this little fellow will not attack a healthy green tree, but he will get busy on the first sign of decay or loss of vitality. As an instance, he will start boring a healthy tree a few minutes after felling, or take a tree that has been slightly scorched by fire. He will soon get to work, the bark will crack in places and start to rise; this becomes a breeding home and in a year or two the sapwood is useless.

In the case of these buried trees, the probability would appear to be that slight seismic action caused the low land to become too wet for kauri; it would then gradually die, the pinholer would get working, but soon after more violent action upset the forest and sank it under water. This land has since risen six to eight feet above high water and the process is still going on.

In a bend in the river we find this old gum bottom under twelve feet of hard sand stone, in which the slope of the sea beach and tide ripple can be traced.

Again this gum bottom dips down under Mangrove-covered mud flats, once rich in gum.

On the high land side of the river we find this old gum bottom with stumps and tree trunks edging in under twenty to thirty feet of pure yellow clay, while up more than one narrow creek with high clay banks we find huge trees and trunks crossed and recrossed in every direction, a wealth of timber that may yet be recovered

We follow this gum bottom, more or less, all over the harbour. In some places it can just be traced on hard cement like sandstone. Yet again it dips down through peat, anything from few inches to perhaps six feet, mostly rich in gum, much broken timber, stumps, or an occasional tree trunk. Logs and stumps are in the channel at thirty feet low water.

No doubt this gum bottom dips under the sand bar and could be found on the open beach, as it is found at Matakana, Pakiri, Mangawai, Waipu, and many other places. How far these vast forests extended out to what is now deep water can never be known.

It is hard to understand how this cement-like sandstone was formed, bearing in mind that well preserved vertical kauri roots and gum are found in, amongst, and under it. In one patch of several acres, the gum had been heated or boiled, like clear glass bubbles, or marble size grains, resembling fire opals.

Where dairy herds graze on rich pastures miles inland, this old gum bottom has been found in wells, sunk twenty to forty feet deep. Near by on the crown of some soft rock promontory, perhaps hundreds of feet above sea level, old fissures have been found filled with gum – gum of an age, however, that corresponds with the oldest taken from the adjoining gumfield.

The kauri has been everywhere on this Northern peninsula, high up on the mountain tops, deep down in the coalmines, out in the ocean depths, a wealth of gum lies buried. Ages on ages of forest growth, periods of mild seismic action, periods of violent seismic action, have left a very mixed state of affairs, which although, puzzling, are interesting.