Precambrian Eon
Geologic time preceding the Cambrian Period of the Paleozoic Era is called Precambrian. The Precambrian encompasses that time between the origin of the earth about 4.6 billion years ago and the appearnce of complex forms of life about 570 million years ago. The oldest dated rocks known so far on the earth is 3.8 billion years old. Precambrian rocks underlying all other rocks of the continents yield records of the Earth's early history ; especially such fossils as cyanobacteria are important to understand paleoenvironments and the initial stage of life evolution.
StromatoliteTienshing, China
Early Proterozoic (about 2,000 million years ago)
Stromatolite is a sedimentary structure which has been formed by cyanobacteria. Cyanobacteria had been producing oxygen through their photosynthetic actions, so that the atmospheric composition had been changed. (29cm wide)
Rock of Antarctica
: Biotite-Saphire Marble and Phlogopite-Spinel SkarnSkaren, Soya Coast, Antarctica; Late Proterozoic (about 700 million years ago)
(15.5cm wide)
Ediacara Fauna
right upper : Charniodiscus sp.,
left center : Dickinsonia costata,
right center : Tribrachidium heraldicum,
upper center : Eoporpita medusa,
left under, left upper : Cyclomedusa spp.,
right under : Pseudorhizostomites howchini
Ediacara, Flinders Ranges, Australia ; Late Proterozoic (700million y.a.)
(35cm wide)