Sea levels were high during the Ordovician. Shallow (<50 metres) inland seas were the greatest for which evidence is preserved in the rocks.
During the Ordovician, the southern continents collected into a single continent called Gondwana. Gondwana started the period in equatorial latitudes and, as the period progressed, drifted toward the South Pole. Early in the Ordovician, the continents Laurentia (present-day North America), Siberia, and
Baltica (present-day northern Europe) were still independent continents.
The Ordovician was a time of calcite sea
geochemistry in which low-magnesium calcite was the main marine precipitate of calcium carbonate.