The Boreal Sea was a

Mesozoic The Mesozoic Era is the Era (geology), era of Earth's Geologic time scale, geological history, lasting from about , comprising the Triassic, Jurassic and Cretaceous Period (geology), Periods. It is characterized by the dominance of archosaurian r ...

-era seaway that lay along the northern border of

Laurasia Laurasia () was the more northern of two large landmasses that formed part of the Pangaea supercontinent from around ( Mya), the other being Gondwana. It separated from Gondwana (beginning in the late Triassic period) during the breakup of Pa ...

.World distribution of middle Jurassic ammonites (Upper Aalenian to Middle Bathonian): relationships between biodiversity and palaeogeography - Moyne et al. 175 (5): 513 - Bull...
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References

Historical oceans Prehistory of the Arctic {{palaeo-geo-stub