Cretaceous
Cretaceous
The Cretaceous was the last and longest period of the Mesozoic. Land and sea temperatures rose during the first half of the period; there were tropical swamps in Africa, South America, India, Australia and Europe, coal swamps along the northern shore of Alaska, and hot deserts in Mongolia. Dinosaurs lived above the Arctic Circle and in the Antarctic, enduring the cold of the month-long nights.
Atmosphere
GURPS Dinosaurs p.41
Oxygen content of the air during the Cretaceous may have been as high as 30%. This will make visitors Overconfident, with IQ rolls at -1; it will also hasten corrosion, and increase the risk of fire. Higher oxygen concentrations may also dry out their eyes; roll HT+2 every minute, with every failure reducing Vision by 1. Time travelers from a world with experience of space travel (late TL7+) can protect against this by wearing reducing respirators with goggles.
Climate
In general, the climate of the Cretaceous Period was much warmer than at present, perhaps the warmest on a worldwide basis than at any other time during the Phanerozoic Eon. The climate was also more equable in that the temperature difference between the poles and the Equator was about one-half that of the present. Floral evidence suggests that tropical to subtropical conditions existed as far as 45° N, and temperate conditions extended to the poles.