CHAPTER 15—CENOZOIC EVENTS
CHAPTER OVERVIEW
The Cenozoic Era is divided by most geologists into two periods: the Paleogene and the Neogene. This
“newer” approach represents a move to an equal division of the epochs and also a more natural way of
dividing Cenozoic rocks in Europe. The Cenozoic, although covering only the last 66 million years,
represents major worldwide changes. One such change occurred when the North Atlantic rift extended to
the north, separating Greenland from Scandinavia and thereby destroying the land connection between
Europe and North America. During the late Eocene epoch, Australia separated from Antarctica and then
began its journey to its present location. This is considered the only major continental breakup during the
Cenozoic; however, it appears to have affected climates around the world.
The stratigraphy of the Cenozoic of North America is explored with some of the more noteworthy
exposures: the Gulf Coast, Rocky Mountains, High Plains, Basin and Range, Colorado Plateau, Columbia
Plateau and Cascades, Sierra Nevada, and California are discussed. The sedimentation and deformation
of the Cenozoic outside North America is also discussed in order to complete this phase of Cenozoic
history. Pleistocene Glaciation is a focal point in this chapter which highlights the Glacial and Interglacial
stages in North America and Europe as well as discussing variations in climatic conditions.
LEARNING OBJECTIVES
By reading and completing information within this chapter, you should gain an understanding of the
following concepts:
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Sketch and label the Paleogene and Neogene Periods and the epochs within each.
Discuss the tectonic-climate connection.
Locate on a map the major mountain systems that were formed by the northward moving
African block as it collided with the underside of Europe.
Explain the origin of the following physiographic features of North America: Rocky
Mountains/High Plains, Basin and Range, Colorado Plateau, Columbia Plateau and
Cascades, Sierra Nevada and California.
Describe the formation of the San Andreas Fault.
Explain the orogenic events along the Tethys seaway and the orogenic events that led to the
formation of the Alps, Carpathian, Pyrenees, Apennines, and Himalayas.
Discuss the origin of Lake Molawi and Lake Tanganyika in eastern Africa.
List the four Glacial/Interglacial Stages for North America and Europe from oldest to youngest.
Discuss the impacts of Pleistocene glaciation.
Explain the Milakovich Effect (Theory) and its possible interpretation of the Pleistocene
Glaciation including the three variables in your explanation.
CHAPTER OUTLINE
I.
The Tectonic-Climate Connection
II.
Stability and Erosion Along the North American Margin
III.
Gulf Coast: Transgressing and Regressing Sea
IV.
Tectonics and Erosion in the Rockies
A. Sediment and Mineral Wealth
B. Remarkable Fossils
C. Majestic Scenery
V.
Creating the Basin and Range Province
VI.
Colorado Plateau Uplift
Chapter 15—Cenozoic Events
VII.
Columbia Plateau and Cascades Volcanism
VIII.
Sierra Nevada and California
IX.
The New West Coast Tectonics
X.
Meanwhile, Drama Overseas
A. Northern Europe
B. Rifting Africa
C. Semitropical Antarctica
XI.
Big Freeze: the Pleistocene Ice Age
A. Pleistocene and Holocene Chronology
B. Stratigraphy of Terrestrial Pleistocene Deposits
C. Pleistocene Deep-Sea Sediments
D. Many Impacts of Pleistocene Glaciation
1. Shifting Sea Level
2. Depressed Crust Rebounds
3. Redirecting Mighty Rivers
4. Forming Lakes, Great and Small
5. Washington’s Alien Land: the Channeled Scablands
6. Windblown Sediment
XII.
Why Did Earth’s Surface Cool?
A. Milankovitch Cycles
B. Earth’s Albedo
C. Other Factors
XIII.
Cenozoic Climates
Chapter 15—Cenozoic Events
KEY TERMS (Pages 451–485))
albedo (482): The fraction of solar energy reflected back into space is termed the Earth’s albedo.
channeled scablands (480): With the recession of the glacier, the ice dam broke, and tremendous
floods of water rushed out catastrophically across eastern Washington, causing severe erosion and
depositing huge volumes of gravel, boulders, and cobbles. The dissected region is appropriately termed
the channeled scablands. This event was associated with the formation of Pleistocene lakes in the
northwestern corner of the United States.
discoaster (475): Calcareous, often star-shaped fossils believed to have been produced by goldenbrown algae related to coccoliths.
kettle (479): A depression in glacial drift that is formed by the melting of a detached block of ice that was
buried in the drift.
Little Ice Age (476): The four-century period (AD 1540 and 1890) when temperatures were often 2 to 4°
degrees Fahrenheit cooler than today in Europe and the United States.
loess (480): Deposits of thick layers of windblown silt formed from fine-grained glacial sediments that
have been spread across outwash plains and floodplains by wind transportation.
milankovitch cycles (481, 482): The hypothetical long-term effect on world climate caused by three
known components of Earth motion. The combination of these components provides a possible
explanation for repeated glacial to interglacial climatic swings.
Neogene period (452): A subdivision of the Cenozoic that encompasses the Miocene, Pliocene,
Pleistocene, and Holocene epochs.
oil shale (458): A dark-colored shale rich in organic material that can be heated to liberate gaseous
hydrocarbons.
Paleogene (452): A subdivision of the Cenozoic that encompasses the Paleocene, Eocene, and
Oligocene epochs.
Pleistocene Ice Age (473–483): About one-third of the Earth’s land surface became buried beneath more
than 40 million cubic kilometers of snow and ice.
pluvial lakes (479): A lake formed in an earlier climate when rainfall was greater than at present.
precession (481): The way the axis of rotation moves slowly in a circle that is completed every 26,000
years.
stratified drift (476): Deposits of glacial clastics that have been sorted and stratified by the action of
meltwater.
Tethys sea (470): A great east-west trending sea which laid between Laurasia and Gondwonland during
the Paleozoic and Mesozoic from which arose the Alpine-Himalayan mountain range.
till (476): Unconsolidated, unsorted, unstratified glacial debris.
Chapter 15—Cenozoic Events
MULTIPLE-CHOICE QUESTIONS
1.
During the Cenozoic, the interiors of most continents were
a. covered by epeiric seas.
c. dry land with some lacustrine (lake)
sedimentation.
b. regions of evaporite deposition.
d. regions of mountain building.
2.
The Columbia Plateau formed as a result of
a. block faulting and uplift.
b. volcanic eruptions resulting in volcanic edifices which were later eroded to a flat-lying plateau.
c. accumulation of thick successions of basaltic lavas erupted from fissures.
d. glacial scouring of bedrock by continental glaciers of the Pleistocene.
3.
The fraction of solar energy received by a planet from the sun that is reflected or reradiated back
into space is called the
a. albedo.
c. insolation.
b. ecliptic.
d. refraction.
4.
The location of the type section for most of the Cenozoic epochs is the
a. Ouachita Mountains.
c. Michigan Basin.
b. Paris Basin.
d. Trans-Continental Arch.
5.
During a volcanic eruption, sometimes clouds of hot gases and pyroclastic debris move rapidly
down the slope of the volcano and deposit thick layers of volcanic debris. These are called
a. lahars.
c. debris flows.
b. nuée ardente.
d. ignimbrites.
6.
Recent volcanic activity in the Cascade Mountains is a response to the subduction of the
a. Farallon plate.
c. Andean plate.
b. Cocos plate.
d. Juan de Fuca plate.
7.
The Red Sea and the Gulf of Aden were formed when
a. Arabia rifted from Africa.
c. Madagascar and Australia rifted from Africa.
b. Africa collided with Arabia.
d. Europe collided with northern Africa.
8.
Which of the following does not represent one of the epochs of the Paleogene?
a. Paleocene
c. Oligocene
b. Eocene
d. Pliocene
9.
Freshwater limestones, fine, evenly laminated shales (varves), and oil shales are characteristic of
what Eocene Formation?
a. Owl Creek Formation
c. White River Formation
b. Green River Formation
d. Fort Union Formation
10.
The Pyrenees and the Atlas Mountains were formed by
a. the collision of northern Africa with Europe.
b. thrust faulting which displaced strata from southwestern Europe on to the northern African plate.
c. sedimentation along the Tethys Seaway.
d. rifting of Eurasia from Gondwanaland.
11.
Windblown, fine-grained, quartz and silt grains that form extensive deposits in China and North
America are called
a. gangue.
c. shale.
b. loess.
d. diatomite.
12.
Sedimentary particles deposited by glaciers and then reworked by runoff and meltwater is called
a. till.
c. moraines.
b. stratified drift.
d. eskers.
Chapter 15—Cenozoic Events
13.
Sedimentary layers deposited in ancient lakes that correspond to yearly cycles of deposition are
called
a. drift.
c. varves.
b. till.
d. rills.
14.
The order of glacial stages/interglacial stages in the Pleistocene from oldest to youngest is
a. Nebraskan, Kansan, Illinoian, Wisconsin. c. Nebraskan, Illinoian, Kansan, Nebraskan.
b. Wisconsin, Illinoian, Kansan, Wisconsin. d. Wisconsin, Kansan, Illinoian, Nebraskan.
15.
G. Milankovich’s theory for Pleistocene Glaciation, which accounts for the Earth’s movements, is
based on three variables. The second variable refers to the way the axis of rotation moves slowly in
a circle that is completed about every 26,000 years. It is called
a. inclination.
c. orbital spin.
b. declination.
d. precession.
16.
A period of cooler and drier climatic condition from 1540 to 1890 AD was called the
a. Messinian event.
c. “Little Ice Age.”
b. Milankovich hypothesis.
d. interglacial period.
17.
The overall global temperature of the Cenozoic started to decrease during what geologic period?
a. Eocene
c. Miocene
b. Oligocene
d. Pleistocene
18.
The best record of Cenozoic strata in North America is found in the _______________ where eight
transgressions and regressions are recorded.
a. Colorado Plateau
c. Gulf of Mexico Coastal Plain
b. Cascade Range
d. Atlantic Gulf Coast
19.
The Florissant Fossil Beds were produced during the _________________; it recorded the eruption
of volcanoes that produced ash that buried countless insects, leaves, spores, pollen, fish, and some
birds.
a. Eocene
c. Miocene
b. Oligocene
d. Pliocene
20.
Crustal movements began during the early _________________ that caused the elevation of the
Sierra Nevada along a great fault producing the Basin and Range Province.
a. Eocene
c. Paleogene
b. Oligocene
d. Neogene
Chapter 15—Cenozoic Events
FILL IN THE BLANK
1.
The western edge of North America during most of the Cenozoic was the site of an eastwarddipping subduction zone. The oceanic plate that was being fed into the subduction zone has been
named
.
2.
The Fort Union Formation, approximately 1800 meters thick, holds immense tonnage of what ore in
its lower levels? _____________________
3.
The most complete and best record of Cenozoic strata in North America is found on the
.
4. The recent activity at Mount St. Helens and the older eruptions that gave rise to the volcanic peaks
of the Cascades are the surface expression of the American plate and the
plate.
5.
These calcareous, often star-shaped fossils believed to have been produced by golden-brown algae
related to coccoliths are called
.
6.
The basin that is not only a sedimentary basin, but a structural basin as well and represents the type
area for most of the Cenozoic epochs is called
.
7.
The lakes that were particularly numerous in the northern part of the Basin and Range Province of
North America, where faulting produced more than 140 closed basins, were called
8.
The large scale physiographic province of the late Tertiary faulting that included portions of Nevada,
Arizona, New Mexico and southern California was called
and
Province.
9.
West of the Columbia Plateau lies an uplifted belt that was also the site of extensive volcanic
activity. It was further characterized by outpourings of more viscous lavas that resulted in what
mountains?
10.
The interfingering of permeable sands and impermeable clays provide ideal conditions for the
eventual entrapment of oil and gas in what part of the Cenozoic Province of North America?
11.
During the Oligocene explosive volcanic activity in this area of Colorado produced a great deal of
ash, which settled to the bottom of a neighboring lake, burying thousands of insects, leaves, fish,
few birds, and trees. This area is called the
.
12.
The term used in Europe to describe dark, siliceous shales, poorly sorted sandstones, and cherts
that accumulated between elongated submarine banks is
.
13.
The best-known feature resulting from the linked processes of uplift and erosion on the Colorado
Plateau is
of the Colorado River.
14.
The sedimentary feature which consists of a thin, dark winter layer and a light-colored summer layer
representing the depositional record of a single year is
.
15.
The Cenozoic Era is divided into two periods: the _________________ and the
________________.
.
Chapter 15—Cenozoic Events
TRUE-FALSE
1.
The great thickness of sediment (10,000) that has accumulated during the Cenozoic in
the Gulf Coast and Gulf of Mexico indicates that the area experienced considerable
subsidence during deposition.
2.
For the most part, the Lower Tertiary sediments of the Rocky Mountain region consist of
gray siltstones, sandstones, carbonaceous shales, lignite, and coal.
3.
The Basin and Range Province occupies a broad zone from Nevada and Western Utah
southward into Central Mexico.
4.
During the Miocene, the Columbia Plateau formed volcanic activity.
5.
Mount Kilimanjaro and Mount Kenya are isolated remnants of a great thrust sheet caused
by the collision of India against eastern Africa.
6.
According to the plate tectonic hypothesis, the crustal compression that resulted in the
formation of the Pyrenees and Atlas Mountains was the result of a collision between
northwestern Africa and southwestern Europe.
7.
A branch of the Indian Ocean opened between Arabia and Africa during the Cenozoic that
created the Gulf of Aden and Red Sea.
8.
The Tethys Seaway of the Mesozoic was closed by plate tectonic collisions in the
Cenozoic.
9.
Lake Malaui and Lake Tanganyika, in eastern Africa, are the result of water accumulation
in downfaulted blocks of crust formed during the current rifting activity in that region.
10.
The Himalayan Mountains formed as a result of the collision of India with Eurasia during
the Cenozoic.
Chapter 15—Cenozoic Events
ANSWER KEY
Multiple Choice
1. c
2. c
3. a
4. b
5. b
6. d
7. a
8. d
9. b
10. a
11. b
12. b
13. c
14. a
15. d
16. c
17. c
18. c
19. b
20. d
Fill Ins
1. farallon plate
2. coal
3. Gulf Coastal Plain
4. Juan deFuca
5. discoasters
6. Paris basin
7. pluvial lakes
8. Basin, range
9. cascade range
10. Gulf Coastal Plain
11. Florissant Flora
12. flysch
13. Grand Canyon
14. Varves
15. Paleogene
True/False
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
T
T
T
T
F
T
T
T
T
T
Chapter 15—Cenozoic Events
RESPONSES TO QUESTIONS ACCOMPANYING SELECTED FIGURES
FIGURE 15–1 (p. 453) Although not specifically mentioned in the chapter, one would surmise that fossils
would be the evidence for a milder Antarctic climate during the early Tertiary. Such evidence includes
actual spore and pollen fossils from early Tertiary rocks in Antarctica. Before Antarctica separated from
Australia, it was warmed by currents moving toward the continent from lower latitudes. With separation,
cold polar currents entered the breach between the two landmasses, resulting in frigid conditions.
FIGURE 15–6 (p. 456) In order to accommodate 27,000 feet of sediment in a shallow depositional basin,
the basin would have had to subside as it was being filled.
FIGURE A (p. 461) Bedrock of impermeable clays and shales, the absence of a protective cover of plants,
and infrequent heavy rains are the primary conditions under which badlands are formed.
FIGURE 15–19 (p. 466) Careful examination of the photograph reveals that the lava flow is covered by the
pyroclastics (tephra). Therefore, the lava flow occurred before the eruption of the pyroclastic material.
FIGURE 15–21 (p. 466) The vertical cracks constitute columnar jointing, a feature frequently formed in
cooling lava flows.
FIGURE 15–32 (p. 472) The outcrop pattern shows youngest rocks in the central area and older rocks
encircling the central area, as is typical of erosionally truncated basins.
FIGURE 15–35 (p. 474) A line indicating the direction of glacial movement would extend roughly from
lower left to upper right.
FIGURE 15–38 (p. 476) Ground moraine is likely to be less well sorted, as it has often not been winnowed
and sorted by meltwater.