The Cretaceous was about living it large in a greenhouse world. It was warm everywhere: CO2 levels were high and sealevels were at their highest. Animals grew big. It was the age of giant dinosaurs, giant dragonflies, and giant fish. The high global temperatures and chemistry of the cretaceous oceans, led to regular and wide spread algal blooms. The calcite plates of the algae are preserved as chalk cliffs throughout most of Northern Europe.