The Cenozoic Era

1.8

5.0

23.7

33.5

54.5

66.4

Ma

Major themes of the Cenozoic

• Earth– overall climatic cooling (“greenhouse to icehouse”)– changes in ocean circulation– Pangea breakup continues but slows– changes in position of land and sea– changes in oceanic nutrient levels

• Life– diversification and dominance of mammals– dominance of angiosperms– continuation of the Mesozoic Marine Revolution

The Earth in the Cenozoic

• Changes in position of land and sea– destruction of Tethys– effects on climate– effects on ocean circulation– land bridges

• Changes in ocean circulation– cooling more vigorous circulation– continental position new current patterns

• Overall climatic cooling– continental position S. Hemisph. glaciation

Glomar Challenger

JOIDES Resolution

The Deep Sea Drilling /Ocean Drilling Project(DSDP/ODP)

Oxygen isotope paleothermometry

• O isotope fractionation is temperature-dependent (warmer temps more 16O, less 18O)

• expressed as ppt relative to PDB (Pee Dee Belemnite)

• need to correct for ice volume (more glacial ice SW enriched in 18O)

Oxygen isotope paleothermometry

18O negative =warmer

18O positive =cooler

Major climate events of the Cenozoic

• Late Paleocene Thermal Maximum (LPTM)

• Eocene-Oligocene cooling / Antarctic glaciation

• Miocene cooling

• Pleistocene glaciation

The carbon isotopic excursion at the P-E boundary

Possible cause(s) for the LPTM

more hydrothermal activity

more CO2 warming release of

methane clathrates more CO2

warming

Methane Hydrates

Major climate events of the Cenozoic

• Late Paleocene Thermal Maximum (LPTM)

• Eocene-Oligocene cooling / Antarctic glaciation

• Miocene cooling

• Pleistocene glaciation

The breakup of Gondwanaland:the death of Tethys and the formation

of the Circumantarctic Current

• India collides with southern Asia (ca. 55 Ma)

• Australia separates from Antarctica (ca. 58 Ma)

• South America separates from Antarctica -- the Drake Passage (33.5-23.5 Ma)

Major climate events of the Cenozoic

• Late Paleocene Thermal Maximum (LPTM)

• Eocene-Oligocene cooling / Antarctic glaciation

• Miocene cooling

• Pleistocene glaciation

The rise of mammals

Eocene Miocene

The evolution of whales

http://www.indiana.edu/~ensiweb/images/whal.amb.jpeg

An artist's rendering of Rodhocetus. This mammal lived near the

shores of the Tethys Sea, between Asia and the South

Asian subcontinent, about 47 million years ago.

The real fossil bones of the walking and swimming whale, Ambulocetus natans, are spread out in this picture with a sledgehammer for scale. The skeleton was about 12 feet long and is about 49 million years old. It was found in Pakistan.

Basilosaurus, Eocene of Alabama