Cretaceous

North America circa 70.4 mya

GURPS Dinosaurs p.40

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.

Geology

GURPS Dinosaurs p.41

The Cretaceous was much longer than the two preceding periods. As it began, Pangaea was separating into two smaller supercontinents: Laurasia (North America, Europe and Asia) and Gondwana (South America, Africa, India, Antarctica and Australia). These, in turn, broke up. By the end of the period, most of the continents were close to their present positions. Alaska and Siberia were joined by a land bridge, as were Canada, Greenland, and western Europe. Antarctica and Australia were still connected, India was still an island, Central America was a string of islands, and Europe and Africa were separated by the Tethys Sea. In North America, the Rocky Mountains formed, and sediments washed from the highlands were carried by rivers into a shallow mid-continental sea, forming a well-irrigated floodplain where dinosaurs and other animals flourished.

Mechanics

• As a general rule: [Cretaceous Natural Skill] defaults to [Modern Natural Skill]-4, or [Modern Paleo Skill]-2; example: Zoology vs Paleozoology. Ref: GURPS Lands Out of Time.