Cenozoic Era

Geologic Time

•Eons:•Hadean

▫4.5-3.8 bya•Archaean

▫3.8-2.5 bya•Proterozoic

▫2.5 bya – 543 mya

•Phanerozoic•543 mya-

present

• At only 66 million years long, the Cenozoic is only 1.4% of all geologic time▫or only 20

minutes on our hypothetical 24-hour clock for geologic time

Geologic Time in 24-hours

•When the Cenozoic began, semitropical (angiosperm) forests covered much of North America, and many mammals dwelled in these forests

•Many event that began during the Cenozoic continue to the present, including ▫the ongoing erosion of the Himalayas in Asia

and the Andes in South America,▫ the origin and evolution of the San Andreas

fault, ▫and the origin of the volcanoes that make the

Cascade Range.

Cenozoic Events

•Geologists divide the Cenozoic Era into two periods of unequal duration▫The Paleogene Period

66 to 23 million years ago includes Paleocene, Eocene, and the Oligocene

epochs▫The Neogene Period

23 million years to the present Includes Miocene, Pliocene, Pleistocene,

Holocene epochs•Older system:

▫Tertiary and Quaternary periods

Neogene and Paleogene

•Vast exposures of Cenozoic sedimentary and igneous rocks in western North America ▫record the presence of a shallow sea in the

continental interior, ▫terrestrial depositional environments, ▫lava flows, ▫and volcanism on a huge scale in the Pacific

Northwest.

Cenozoic Rocks Are Accessible

Paleocene Fort Union Formation, Montana

Wasatch Formation, Bryce Canyon

Miocene Lovejoy Basalt, California

•The progressive fragmentation of Pangaea accounts for the present distribution of Earth's landmasses

•Because the geographic locations of continents profoundly influence the atmosphere and hydrosphere, moving plates also directly affect the biosphere

Cenozoic Plate Tectonics

•During the Triassic Period

Paleogeography of the World

•During the Jurassic Period

Paleogeography of the World

•During the Late Cretaceous Period

Paleogeography of the World

•Spreading ridges such as the Mid-Atlantic Ridge and East Pacific Rise were established, along which new oceanic crust formed and continues to form

•However, the age of the oceanic crust in the Pacific is very asymmetric, because much of the crust in the eastern Pacific Ocean basin has been subducted beneath the westerly moving North and South America plates

Spreading Ridges

Age of Ocean Basins

•Eocene Epoch

Cenozoic Paleogeography of the World

•Miocene Epoch

Cenozoic Paleogeography of the World

•Present Day

Cenozoic Paleogeography of the World

•Another important plate tectonic event ▫Northward movement of the Indian plate

and its eventual collision with Asia•Simultaneous northward movement of the

African plate ▫Caused the closure of the Tethys Sea ▫Causes tectonic activity that currently takes

place int an east–west zone from the Mediterranean through northern India

End of the Tethys

•North and South America continued their westerly movement as the Atlantic Ocean basin widened

•Subduction zones bounded both continents on their western margins ▫Situation changed in North America as it

moved over the northerly extension of the East Pacific Rise and it now has a transform plate boundary

Americas Move West