Earth History GEOL 2110

The Cenozoic EraThe Modern World Emerges

Climate and Life

Major Concepts• Greenhouse conditions that prevailed in the Cretaceous

continued into the Early Cenozoic. But dramatic cooling episodes began in the late Eocene. This appears to be due to changes in ocean circulation as Pangea continued to break apart.

• This climate change resulted in a dramatic change in the biosphere which change from tropical jungles in the early Cenozoic to grasslands, savanahs, and temperate forests in the Late Cenozoic.

• After the Cretaceous extinctions of the dinosaurs, mammals saw an explosive radiation . The change over from jungles to grass lands also caused a change from leaf-eating to grazing mammals with more speed.

Summary of the Cenozoic

PEOMPP

Climate Change in the Cenozoic

Methane Degassing Event

Degassing of Methane Hydrates in Early Eocene

USGS map of known and suspected methane hydrate deposits

Seismic profile offNorth Carolina

3000 m

Methane Plumes

Degassing of Methane Hydrates in Early Eocene

Deep-sea plume of methane escaping from the sea floor

Climate Change in the Cenozoic

The Great Eocene-Oligocene Cool Down

Separation of Australia and SA from Antarctica triggers Glaciation and Major Extinction of Warm-climate Species

The Great Eocene -Oligocene Cool Down

Climate Change in the Cenozoic

Mid-Miocene Cool Down

Mid-Miocene Cool Down (15 Ma)Arctic – Atlantic Connection Established

Miocene 20-15 Ma

Cool Down Continues into the Pliocene and into Today

Climate Change in the Cenozoic

Climate Change Affects the Biosphere

Warm, lush forests/jungles of the Eocene give way to ….

Temperate grasslands and

savannas of the Miocene

Mammalian Evolution

“In the Late Cretaceous, no mammal was larger than a house cat. By the Eocene (40Ma) all modern orders of mammals had evolved with some the size of a rhinoceros or elephant”

Adaptation to the Mid-Cenozoic Climate

Longer–limbed runners Better eye sightCud-eaters Hoofs replace toesHigh crowned teeth that continue to grow

The Gondwanan ContinentsNatural Laboratories of Speciation

Ecological Convergence

Great American InterchangeWhen Migration was North to South

Isthmus established in Mid-Pliocene (4Ma)

South Americans

North Americans

Fig. 15.51b

Next Lecture

The Pleistocene EpochThe Ice Age

QUIZ on Chapter 16p. 465-485

and MNaG-Q