Archaean (

Archaean Archaean

) is the oldest period in geological history. From a biological point of view, this is primitive.

The initial stage of life and biological evolution, when there were only a few prokaryotes,

They only left some fossil records.

From a non-biological point of view,

Archean crust is very thin,

The geothermal gradient is steep,

Volcanic magma activity is intense and frequent,

Rock strata usually suffer from deformation and metamorphism,

Both the atmosphere and hydrosphere lack free oxygen,

The period of forming a series of special sediments;

Is also a

The formation and continuous growth period of silicon-aluminum crust is also an important metallogenic period.

Proterozoic (

Proterozoic era

There have been some large-scale thick surfaces in the early days.

Relatively stable continental plate.

Therefore,

As far as lithospheric structure is concerned, Proterozoic is more obvious than Archean.

The characteristics of stability are introduced.

The atmosphere in the late Early Proterozoic already contained free oxygen,

And with

With the increasing prosperity of plants and the strengthening of photosynthesis, the oxygen content in the atmosphere is increasing.

The middle and late Proterozoic algae plants flourished, which was obviously different from Archean.

Sinian (

Sinian Period

) is a unique stage of geological history in the late Proterozoic. from

The evolution of biology,

Sinian contains crustless metazoan fossils,

And unreliable.

Proterozoic and Proterozoic animal fossils have important differences.

But it is rich in fossils of animals with shells.

Compared with CAMBRIAN,

The fossils contained in Sinian system are not only monotonous,

Small in number, distributed in ten places.

Integral is limited.

Therefore,

At present, it is impossible to use the animal fossils in it for effective biostratigraphic research.

The most prominent feature of Sinian biology is that there are many afterlife without hard shell in the later period.

Finally, a small number of small animals with shells appeared. Advanced algae further flourish, micro.

Some new types of somatic plants have appeared,

Stromatolites flourished in the early Sinian,

Late number

The number and variety suddenly declined.

According to the tectonic conditions of the lithosphere,

On the surface of the Sinian earth

There are several big ones,

Relatively stable continental plates,

It is already a typical cover above it.