Both surface and deep sea waters warmed, even near Antarctica.
Deep circulation remains sluggish.
High percentage of the plant species had smooth margins . Equatorial zones were largely covered by oceans, allowing more absorption of solar heat. Less area covered by snow and ice, more exposed land, allowing more absorption of solar heat Presence of dense forests at high latitudes. Forests have low albedo, trap heat and moisture. Intense volcanism at mid-ocean ridge associated with opening of North Atlantic may have released greenhouse gases.