Cenozoic Earth History I
The Cenozoic Era
Spans the 65.5 Ma, from the end of the
Mesozoic to today. There is not
agreement in the Earth science
community about whether the
Cenozoic should be sub-divided into
Tertiary and Quaternary or into
Paleogene, Neogene and Quaternary.
Both classifications are used.
The Cenozoic Era
The Tejas transgression began and ended during the Paleogene. Starting at about the middle
of the period, cooling at both poles led to a long period of global cooling and sea level fall. The
fall in sea level led to the development of many of the Atlantic Coastal Plain’s interesting
geologic features like a stair-step series of scarps (paleo-shorelines) and terraces (wavescoured sea floor).
By the Neogene, the Earth’s polar climate had cooled to the point that both sea ice and
continental glaciers began to grow. By the Neogene, Earth’s climate was locked into “Icehouse
Earth” – the Earth’s climate was (and still is) cold enough that minor changes in the shape of
the planet’s orbit causes extensive ice ages.
The Atlantic Coastal Plain
The flat-lying Atlantic Coastal Plain (ACP)
contains a thick sequence of sediments
weathered from the Appalachians and
deposited during the Zuni (Cretaceous) and
Tejas (Eocene) transgressions.
The ACP strata at the surface are
progressively younger, with Cretaceous and
Eocene strata cropping out farthest inland. The
ACP sedimentary wedge thickens toward the
ocean, reaching a thickness of several
kilometers in offshore canyons.
The Atlantic Coastal
Plain Scarps and
Terraces
The scarps mark places
where coastal erosion
occurred in the past. In other
words, they mark the
positions of shorelines in the
past.
The terraces were formed by
slightly offshore erosion and
deposition in the shallow
ocean.
Geologic Provinces of the Southern Appalachians
Appalachian Plateau
Relatively flat lying
sedimentary rocks
deposited during the major
transgressions and
orogenies of the Paleozoic.
The hilly topography is
controlled by river
drainage.
Coal in the Appalachian Plateau strata are targets for strip mining and mountaintop
removal mining because it is relatively flat lying seams.
Geologic Provinces of the Southern Appalachians
Valley and Ridge
The deformed and faulted
sedimentary rocks of this
province were deposited at
the same time as the flat
lying rocks of the
Appalachian Plateau.
These strata were deformed and faulted by the great Alleghanian Orogeny, which shoved
giant blocks westward for dozens of miles. These blocks are bounded by very large
thrust faults.
Geologic Provinces of the Southern Appalachians
Blue Ridge
This province contains
primarily Proterozoic aged
plutonic and metamorphic
rocks, including parts of
the Grenville orogen.
The amount of uplift necessary to expose these deep crustal rocks is on the kilometer
scale. All three Paleozoic orogenies contributed to this massive uplift.
Geologic Provinces of the Southern Appalachians
Peidmont
Usually heavily
weathered igneous and
metamorphic rock similar
to the Blue Ridge as well
as rocks that formed
during the rifting of
Pangaea (rift basin
sediments and igneous
dikes).
Piedmont Province rocks underlie the sedimentary deposits of the Atlantic Coastal
Plain.
Geologic Provinces of the Southern Appalachians
Atlantic Coastal Plain
Lightly lithified and
unconsolidated sediment
deposited during marine
transgressions in the
Cretaceous Period and
Cenozoic Era.
The province extends
into the Atlantic Ocean to
the edge of the
continental shelf.
This sedimentary material is more easily eroded than crystalline rock, so the eastern
boundary is a “fall zone”, where the gradients of rivers steepen suddenly as they dig
into the softer material of the coastal plain.
Fall Zone
Atlantic Coastal Plain Arches
and Embayments
The eastern margin of North
America has been folded into a
series of arches and
embayments by tectonism
associated with formation of the
Caribbean plate and persistent
northward movement of Cuba.
The bays fill with thick packages
of sediment when sea level is
high.
Eastern North America is presently a passive continental margin
Ultimately oceanic crust will break along the continental margin and
subduction of Atlantic basin crust will begin, just as it did with the Iapetus
Ocean during the Paleozoic.
The Western Margin of North America
The Farallon Plate continued to subduct under North America until today
only the Juan de Fuca and Cocos plates remain. Along the way, many,
many terranes that were originally embedded in the Farallon Plate became
part of North America. The subduction of the Farallon-Pacific spreading
center caused many geologic changes, including the establishment of the
San Andreas fault system
An eastward-advancing wave of hot mantle caused...
Extension that
formed the
Basin and Range
Wind River Range,
a Laramide uplift
Cretaceous-Tertiary
Laramide uplift
of Archean crust
that formed the
Rocky Mountains
Uplift of the
Colorado Plateau
E-dipping Permian (left), Triassic (red) and Jurassic (tan) sandstone beds
(right) on the E Flank of the Wind River Range (a Laramide Archean
basement uplift). View toward the NW from Red Canyon Overlook near
Lander, Wyoming
Oregon Trail
Cascade
Range
Centers of
Cenozoic
Cordilleran
Volcanism
Columbia plateau
flood basalts
Yellowstone
hot spot
Snake River
Plain
Arizona
volcanic
field
San Juan
volcanic
field
Columbia Plateau, Snake River Plain, and Yellowstone: Products of the
Yellowstone Mantle Plume Hot Spot
Columbia River Plateau
Northwestward movement of N. A. over the hot spot in the Mid Tertiary
caused eruption of the Columbia Plateau flood basalts. Then N. A. began
moving toward the SW, forming the hook-like shape of the Snake River Plain
flood basalts
Yellowstone
Calderas
Island Park Caldera
Erupted the Huckleberry
Ridge tuff 2 Ma
Henry’s Fork Caldera
Erupted the Mesa Falls
tuff 1.3 Ma
Yellowstone Caldera
Erupted the Lava Creek
tuff 0.6 Ma
Comparison of Volumes of Pyroclastic Eruptions
Cenozoic
Volcanism
in the
Cascade
Range
Subduction of the Juan de Fuca plate along the Cascadia subduction zone
is responsible for the Late Tertiary to recent volcanism of the Cascade
Range volcanoes
San Francisco Mountains, Arizona
Late Cenozoic volcanism formed the San Francisco Mountains
Volcanism ceased ~ 1200 years ago
They are remnants of a stratovolcano that blew its top
Earth’s Major Orogenic Belts
The Circum-Pacific and Alpine-Himalayan orogenic belts, Earth’s present-day
major mountain building belts
The Alpine-Himalayan Orogenic Belt
Volcanism, seismicity, and deformation in the Alpine-Himalayan orogenic belt
extends eastward from Spain through the Mediterranean region into
Southeast Asia
The tectonism, due to collision of the Arabian, African and Indo-Australian
plates with the Eurasian plate,
caused closure of
the Tethys sea
Eocene (50–40 Ma
Miocene (25–15 Ma
The Alpine Orogeny
Is occurring in response to northward movement of the African and Arabian
plates toward southern Europe
The convergence is causing deformation along a linear zone from Spain
eastward through Greece and Turkey and along Africa's northwest coast
Products of the Alpine Orogeny
Alps (France, Germany, Switzerland)
Pyrenees (Spain and France)
Apennines (Italy)
The Alps in
Southern Germany
Italy and Greece
Subduction of Mediterranean crust under Italy, Greece, and Turkey continues
to cause volcanism and seismicity
In 1999 an earthquake killed 17,000 people in Turkey
Mount Vesuvius, Italy, has erupted
80 times since it destroyed Pompeii
in A.D. 79
Mount Etna, Sicily, is
Earth’s most active volcano
The Mediterranean Basin
Most of the water flows into the Mediterranean Sea from
the Atlantic Ocean through the Strait of Gibraltar
Northward advance of the African plate ~ 6 Ma closed
the Strait of Gibraltar, caused the Sea to dry up
When the dam broke, a colossal flood from the Atlantic
ocean rushed into the basin and re-filled the sea
The Circum-Pacific Orogenic Belt
Subduction of the Cocos plate under western Central America is causing
mountain-building and volcanism
Subduction of the Nazca plate under western South America is causing
mountain-building and volcanism
Subduction of the Pacific plate under western Asia is causing mountainbuilding and volcanism in Japan and the Philippians
Global Cooling and Warming Since the Archean
Paleogeography
during the
Permian Ice Age
Global Cooling and Warming Since the Cretaceous
The Pleistocene
“Ice Age”
Changes in Sea
Surface
Temperatures
Since the Eocene
High
Pleistocene Ice Ages and Interglacial Intervals
The Pleistocene began 1.6 Ma, ended 10,000 years ago
Four major periods of widespread glaciation occurred, were separated by
warmer interglacial periods
Two Notable Pleistocene Terminal Moraines
End moraines
Cape Cod
Long Island
Glacial and Pluvial Lakes
Glacial Lake
Missoula
Wave-cut shore lines cut
by Glacial Lake Missoula
Channeled Scablands formed
by the Missoula flood
Great Salt
Lake
Pluvial Lake
Bonneville
Pleistocene Glaciation of the Northern Hemisphere
Maximum Extent of glaciation
in the Northern Hemisphere
Climate Belts
Sea Level Change during the Past 20,000 Years
Global warming has been
occurring for 17,000 years
Positions of the coastline of North America during the Ice Age and
if the ice sheets melt
What is thought to...
...have caused the Pleistocene Ice Age?
Formation of Central America deflected the Gulf Stream and moist air
northward, produce more snow
Northward movement of North America and Eurasia provided more surface
for snow accumulation
...also cause/contribute to occurrence of ice ages?
Milankovitch cycles, natural periodic changes in
Earth’s orbital eccentricity
Tilt of Earth’s axis
Precession of Earth’s axis, of the equinoxes
Cause periodic changes in the amount of sunlight at high latitudes
Lead to natural periods of global cooling and warming
Excessive volcanism, etc.
Milankovitch Cycles
A change in Earth’s orbital eccentricity
occurs every 100,000 years
A 2° change in tilt of Earth’s
axis occurs every 41,000 years
A precession of Earth’s
axis occurs every
23,000 years