Ordovician
= Ordovician
{c}
A geological period preceding the <Silurian>. Its late interval includes a major <mass extinction> associated with glaciation, changes in <eustatic sea level change> and later marine oxygen stress.
= Ordovician
{c}
A geological period preceding the <Silurian>. Its late interval includes a major <mass extinction> associated with glaciation, changes in <eustatic sea level change> and later marine oxygen stress.