Henderson Bay Fossil Trees

Henderson Bay is a 5 kilometre sweep of sand with dunes that back up against, and partially cover, a terrace of older dunes and shallow marine sands. These older, more consolidated deposits include an upper layer of dark, carbon rich, peaty soils with tree stumps and roots in growth position. Species that have been identified here include manuka, kanuka, rimu, totara and kauri. Some kauri gum has been dated at around 30 000 to 34 000 years old, which was during the last ice age when sea levels were about 120 metres lower than today.
Isolated rounded pebbles can be found within the peaty layer. These are similar in shape and size to the numerous loose pebbles that can be seen in places scattered over the terrace surface. Some of these have been etched by the wind, (ventifacts) showing that they have been in place for a considerable time. Some researchers have interpreted these loose pebbles as representing a tsunami deposit from a major event several hundred years ago.
Hard rusty coloured crusts can be seen within the consolidated sands, and stick out above them. These have been sculpted by the wind in places to create interesting looking, but very fragile sculptures.

The beach, dunes and terraces are an ever changing environment. The fossil trees and associated soils are well worth investigating. Have a look at the scattered pebbles, as well as those that are within the peats and think about how they could have been deposited up to 30 metres above sea level. Bear in mind also that the pebbles within the peat layers were deposited when the sea was much lower than today.