Chapter 3: Changing Climates 3.1 The Great Cooling Chapter 3: Changing Climates

Cypress Hills an island of forest within a sea of grassland 600-m thick section of sedimentary rock was not removed by the advancing ice sheet rare record of Cenozoic Era sediments provides scientists with a complete record of the last 65 million years of Alberta’s history.

Cenozoic Era Most recent Era on the Geological Time Scale 65 million years ago to present 2 periods: Tertiary Period – 97 % - Quaternary Period – 3%

The Beginning of a Cooling Trend At the end of the Cretaceous Period…. The collision between the North American Plate and the Pacific Plate caused the North American Plate to migrate northward and its climate got colder Eventually it was cold enough to cause glaciers and contribute to the Cretaceous Extinction These glaciers carved jagged edges into the smooth mountain ranges that were formed when the 2 plates initially collided

The Retreating Sea The beginning of the Tertiary Period…. As the sea retreated to the south sediment full of dinosaur fossils was deposited Run off from the new Rocky Mountain Range deposited sediment full of fossils from the bottom of the sea (ex. ammonite)

The Rise of Mammals 65 mya – the surviving mammals after the Cretaceous extinction were mainly rodents 65 mya to 40 mya – mammals diversify and flourish 40 mya – many new mammals appear ancestors of modern hoofed herbivores, flesh-eating carnivores, and large brained primates

The Rise of Mammals 35 mya – grasslands dominate Alberta’s landscape Spread of large herds of grazing species in the late Tertiary Period As Alberta became cooler and drier, the deep and dense roots of grasses help them survive Movement from wetlands let to an environment of giant herds of large grazing animals Rhinoceroses, camels, giant pigs, elephants

Evidence of Cooling Trend Evidence is found in sedimentary rocks Presence of tropical plants and animal fossils in current day Polar regions indicates these places must have been much warmer in the past Absence of tree pollen from current tropical landscapes indicates that the past climate was too cold for trees to survive

Evidence of Cooling Trend Evidence is found in deep ocean sediment Determining the oxygen-18 to oxygen-16 ratio allows average deep ocean temperature to be determined The higher the ratio, the lower the average deep ocean temperature See graph on page 372