Transcript Cenozoic 1 - E. R. Greenman

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 myapresent
Geologic Time in 24-hours
• At only 66 million
years long, the
Cenozoic is only
1.4% of all
geologic time
▫ or only 20
minutes on our
hypothetical 24hour clock for
geologic time
Cenozoic Events
• 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.
Neogene and Paleogene
• 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
Cenozoic Rocks Are Accessible
• 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.
Paleocene Fort Union Formation,
Montana
Wasatch Formation, Bryce
Canyon
Miocene Lovejoy Basalt,
California
Cenozoic Plate Tectonics
• 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
Paleogeography of the World
• During the Triassic Period
Paleogeography of the World
• During the Jurassic Period
Paleogeography of the World
• During the Late Cretaceous Period
Spreading Ridges
• 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
Age of Ocean Basins
Cenozoic Paleogeography of the World
• Eocene Epoch
Cenozoic Paleogeography of the World
• Miocene Epoch
Cenozoic Paleogeography of the World
• Present Day
End of the Tethys
• 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
Americas Move West
• 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