Occasionally some rarer objects turn up on fOssilfinder. One such object is that of a piece of fossil wood.
The paler piece in the bottom of this image is the piece of fossil wood. It stands out amongst the many other sandstone pieces in this image.
Fossil wood has a streaked appearance to it and if broken in cross section tree rings can be seen in the fossil too. There are a variety of different woods, including some from palm trees, although it would be difficult to identify the type of wood from the resolution in the fossil finder images.
Towards the eastern margin there are fossil sites in which fossil wood is abundant. Pieces of wood turn up in the fossil exposures that have been carried in streams or sometimes carried in as raw material for stone tools.
Stromatolites are trace fossils of the biofilms of blue-green algae that grow around an object such as a shell or oyster. As the algal filaments grow outwards, sediment is continually deposited and accreted onto the surface of the algal mat. The stromatolite increases in size and forms distinctive concentric rings if you break the stromatolite in cross section.
This is an earlier stage of stromatolite development that is growing around half of an inch long bivalve.
The outer surface of the fossil stromatolites look quite knobbled in their appearance. These round boulders can sometimes be quite large in the fossil record at Lake Turkana, sometimes reaching a meter wide.
Some of these stromatolites can be up to a meter in diameter.
Stromatolites grow in shallow, hypersaline pools in shore settings, inhospitable to molluscs and other invertebrates that might otherwise graze on the algae. There are no modern examples of stromatolites found today at Lake Turkana, however there are modern marine stromatolites that are in lagoons in Shark Bay in Australia. A 3D model of a stromatolite from 0.7 million year deposits at Lake Turkana can be seen here;
This is a cross section of a stromatolite that has grown up around an oyster shell.
Basalt is a volcanic igneous rock with a crystaline structure. It forms when lava rapidly cools.
It can be hard to distinguish from sandstone, especially when weathered, as certain types are lighter brown in colour.
However, its crystaline structure and hardness mean that broken pieces retain sharper angular edges than sandstone and it has a more reflective look to it. The crystaline structure can often be seen on broken surfaces. Basalt is often quite black in colour but can be different shades of brown.
