Ancient Forest Emerges From Beneath Takapuna Beach
In recent days the sand near low water in the middle of Takapuna Beach, Auckland, has shifted and exposed the long
buried remains of an ancient forest.
Many long-time locals say they have never seen it before, although some of the soft sticky mud that it is buried in has
been uncovered in other parts of the beach on odd occasions in the past.
Auckland geologist Bruce Hayward visited the newly exposed fossil forest this week. “This is an exciting new discovery
and is quite different and much older than Takapuna Reef’s famous fossil forest preserved in the lava flows from Pupuke
Volcano”, he says.
“This new fossil forest consists of many small tree stumps in growth position in an ancient soil. It is clear that the
trees became established on the surface of a thick white rhyolitic ash deposit, and in turn they have been buried and
preserved by another thick creamy-white volcanic ash bed”. Similar thick rhyolitic ash and ignimbrite deposits occur in
a number of low-lying parts of Auckland. Elsewhere they have been dated at close to 1 million years old and were erupted
by gigantic explosive blasts from a volcano in the vicinity of Mangakino, near Taupo.
A similar sequence of white volcanic ash and peat occurs in Shoal Bay and was exposed a few years ago by earthworks when
the Esmonde Rd interchange for the northern motorway was being enlarged. Similar aged fossil forests are permanently
visible in eastern and southern Auckland in low sea cliffs at Pakuranga, Takanini and Waiuku.
“The fossil tree stumps and fallen branches and twigs are black, but they have not been burnt” says Dr Hayward, “instead
they have been carbonised during their preservation and fossilisation. A specialist could study their cell structure and
identify the kinds of trees present. Most of the trees are small and less than 15 cm diameter, but larger trees were in
the neighbourhood as I found a large lump of kauri gum in the ancient soil.”
In places the volcanic ash has weathered to clays and is soft and sticky but in some places it has been hardened by
remineralisation and some of these rocks stick up 30 cm above the present beach level.
History tells us that it will not be too long before the sands shift back and once again bury Takapuna Beach’s hidden
secret – the oldest fossil forest on the North Shore.
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