Fragments of fossilised wood, and at times sections of trees wash out of the clay. Those found on the beach are often broken into sections. On the foreshore however the complete preserved section can be observed. Often containing the borings of Teredina sp., the trees are contained within septarian concretions and are associated with a blueing of the clay. A tree from the rainforest falls into a river and is carried out to sea. It becomes waterlogged and sinks to the bottom. The sunken log becomes a host for small invertebrates (minor ecosystem). Animal and plant material accumulates on the leeward side of the log as it fossilises. This helps the other material to preserve. This is always characterised by a blue clay 'aura' around the log. when the clay is collected and processed, this is an excellent source for fossils. Fossils include:- small fish (teeth,spines,bones,scales and otoliths), bryozoans,crustaceans (crabs, barnacles,ostracods), rarely insects. Worm tubes (serpulids) gastropods, bivalves pterapods, scaphapods etc.