are the fossil deposits of microscopic organisms called cyanobacteria.
They are the oldest fossils in Alberta, at over a billion years old. Their
presence in rocks helps mark the locations of ancient coastlines in Alberta.
many other life forms existed, cyanobacteria thrived and flourished in
shallow coastal pools along most of the earth's shorelines. Growing in
enormous colonies that resembled giant cabbage heads, each colony was
like a mat which often covered an area 10-20 centimetres across. They
grew and died beside and on top of each other, gradually forming massive
reef-like accumulations with heights up to10 metres. As they grew, they
deposited layers of calcium carbonate (CaCO3), producing a laminated structured.
It is these CaCo3 layers that we find, not the soft bodies, which decomposed
after they died. This makes stromatolites a peculiar kind of "trace"
fossil because they do not represent the actual remains of organisms,
but rather the growth and life processes of this primitive type of bacterium.