The Ihumatao Fossil Forest, on the shore of the Manukau Harbour, is such a site. Stretched out along the foreshore are the remains of two fossil forests.
The most visible are the remains of an ancient kauri forest lying prone on the mud flats. Growth rings have shown that the kauris were hundreds of years old when they died.
About 100,000 years ago this forest was killed by the changes in groundwater levels, as the area turned to swampland. The forest was submerged and preserved in the peat swamp and is now becoming exposed by the erosion of the covering soft rock and peat.
Quite visible are fossilised kauri stumps which are often accompanied by their prone, fallen trunks. Some stumps even contain small pieces of kauri gum.
The remnants of the younger forest are situated along the cliff line. This forest grew on the black peat approximately 30,000 years ago; and was obliterated by eruptions from the neighbouring Maungataketake Volcano. Fossilised leaves show that this forest was predominately rimu, miro, hinau, kauri and tanekaha.
The lower layers of ash contain fallen logs and branches and also the hollow moulds of rotted logs. Just to the east of the steps are the remains of a tree killed and buried by volcanic ash that can be seen still standing in the cliff.
To claim this cache:
Visit the site between low and mid tide, tides for Onehunga can be found here
Post a picture (optional) of yourself or your group, with GPSr and tape measure (or measuring implement) clearly visible, in the kauri forest and if possible completing the following activities:
Measure the diameter of at least 3 stumps
Measure the length of at least 1 fallen trunk
Email me the above results along with the number of steps between the car park and the shoreline. Please do not post these results in your log.
Please note that the flats around the forest are muddy and some minor wading may be required, please wear appropriate footwear.
The steps to the beach have been deemed unsafe by the council, however as fast as they fence them off the local fishermen open them up again. Use at your own risk. Access without the steps is difficult, but not impossible.