Transcript Basin and Range

Cenozoic History
• 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
Cenozoic Time
Scale
• In this class we use
– the term Tertiary
Period
– rather than Paleogene
and Neogene Periods
Plate Tectonics
• Three kinds of margins:
– Divergent
– Convergent
• Ocean-ocean
• Ocean-continent
• Continent-continent
Divergent margins
Ocean-ocean convergent margins
Ocean-continent convergent
margins
Continent-continent
convergent margins
Covergent,
more
The Himalayas
• During the Early Cretaceous,
– India broke away from Gondwana
– and began moving north,
– and oceanic lithosphere was consumed
– at a subduction zone
– along the southern margin of Asia
Before India Collided with Asia
• Oceanic lithosphere
– subducted beneath southern Tibet
– as India approached Asia
northern margin of India
southern margin of Tibet
India Collided with Asia
• About 40 to 50 million years ago
• India collided with Asia,
– but because India was to light to subduct,
– it thrust under Asia
Continued Convergence
• Thrusting of Asian rocks
– onto the Indian subcontinent
– accompanied continued convergence
India Moved beneath Asia
• Since about 10 million years ago,
– India has moved beneath Asia
– along the main boundary fault
– Shallow marine sedimentary rocks
• that were deposited along India’s
northern margin
• now form the higher parts of the Himalayas
The Circum-Pacific
Orogenic Belt
Evolution of the Andes Mountains
• Prior to 200 million years ago,
– the west coast of South America
– was a passive continental margin
– where huge quantities of sediment were
deposited
Evolution of the Andes Mountains
• Orogeny began when this area
– became an active continental margin
– as South America moved to the west
– and collided with oceanic lithosphere
Evolution of the Andes Mountains
• Deformation, volcanism and plutonism
continued
The North American Cordillera
• The North American Cordillera
– is one large segment of the circum-Pacific
orogenic belt
– extending from Alaska to central Mexico
• In the United States it widens to 1200 km
– stretching east-west
– from the eastern flank of the Rocky Mountains
– to the Pacific Ocean
Cordillera
• North
American
Cordillera
– and the
major
provinces
– of the
United
States
and
Canada
Sedimentary
Basins in the West
• Locations of
Proterozoic
sedimentary Basins
– in the western United
States and Canada
• Belt Basin
• Uinta Basin
• Apache Basin
Cordilleran
Mobile Belt
Antler Orogeny
in Devonian
Cordillera Evolved
• After Laramide deformation, Cordillera
continued to evolve
– large-scale block-faulting
– extensive volcanism
– vertical uplift and deep erosion
– Basin and Range
• During about the first half of the Cenozoic Era,
a subduction zone was present
– along the entire western margin of the Cordillera,
– but now most of it is a transform plate boundary
– ???
Plate Interactions Continue
http://earth.geol.ksu.edu/sgao/re
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The Laramide Orogeny
• Third in a series of deformational events
– in the Cordillera beginning during the Late
Jurassic
• Late Cretaceous to Eocene
• Differed from the previous orogenies in
important ways
Laramide orogeny
– took place as the Farallon plate,
– buoyed up by a mantle plume
– subducted beneath North America
– at a decreasing angle
– and igneous activity shifted inland
???
Change to Shallow
Subduction
• By Early Tertiary time,
– the westward-moving North American plate
– had overridden the part of the Farallon plate,
– above the head of the mantle plume
• The lithosphere
– immediately above this plume
– was buoyed up,
– accounting for a change
– from steep to shallow subduction
Igneous Activity Ceased
• With nearly horizontal subduction,
– igneous activity ceased
– and the continental crust
– was deformed mostly by vertical uplift
Renewed Igneous Activity
• Disruption of the oceanic plate
– by the mantle plume
– marked the onset
– of renewed igneous activity
Cordilleran Igneous Activity
• The vast batholiths in
• Idaho
• British Columbia
• Sierra Nevada of California
– were emplaced during the
Mesozoic Era
– intrusive activity continued into
Tertiary
http://www.bhc.edu/academics/science/harwoodr/GEOL
102/Study/Images/BatholithsNA.gif
Tertiary
Volcanism
– more or less
continuous in
the Cordillera
– varied in
intensity,
eruptive style,
and location
– ceased
temporarily in
the area of the
Laramide
orogen
Columbia River Basalts are remnants
of a great volcanic event
–
–
–
–
an aggregate thickness of about 2500 m
well exposed in the walls of the deep gorges
cut by the Columbia and Snake rivers
Some of the individual flows were truly phenomenal
• Roza flow alone covers 40,000 km2 and has been traced
about 300 km from its source
~ 20 lava flows of the
Columbia River basalts
exposed in the canyon
of the Grand Ronde
River in Washington
Cascade Range
• Some of the highest mountains in the Cordillera
are the Cascades
– California, Oregon, Washington, British Columbia
• Thousands of volcanic vents are present
– dozen large volcanoes
– Lassen Peak in California
• world's largest lava dome
• Related to subduction of the Juan de Fuca plate
http://www.cr.nps.gov/history/online_boo
ks/resedu/resedu2a.htm
Basin and Range
Basin and Range Province
– ranges are bounded by faults symptomatic of
spreading
– Why spreading here?
– Action of San Andreas?
Colorado Plateau
Colorado Plateau: older source rocks
– Paleozoic
rocks exposed
in the Grand
Canyon,
Arizona
– Mesozoic sedimentary rocks in
the Valley of the Gods, Utah
Colorado Plateau
– Mesozoic sedimentary rocks at Colorado
National Monument, Colorado
Pacific Coast
• Before the Eocene,
– the entire Pacific
Coast was a
convergent plate
boundary
– Farallon plate was
consumed at a
subduction zone
– stretched from
Mexico to Alaska
Change from Subduction
• As the North American
Plate
– overrode the Pacific–
Farallon Ridge,
– its margin became
transform faults
• the San Andreas
• and the Queen Charlotte
– alternating with
subduction zones
Extending the San Andreas Fault
• Further overriding of
the ridge
– extended the San
Andreas Fault
– and diminished the
size of the Farallon–
Plate remnants
• Now only two small
remnants
– of the Farallon plate
exist
– the Juan de Fuca and
Cocos plates
The Continental Interior
• A vast area
called the
Interior
Lowlands
– the Great
Plains
– and the Central
Lowlands
Cenozoic History of the
Appalachian Mountains
• Deformation in the Appalachians has a long
history
– began during the Late Proterozoic
– during Late Triassic time, the entire region
experienced faulting as Pangaea fragmented
Reduced to Plains
• By the end of the Mesozoic
– erosion had reduced the mountains to a plain
across which streams flowed eastward to the
ocean
Appalachians in the Tertiary
• Streams developed across the plains
during the Tertiary
Present Appalachian Topography
• Although these mountains have a long history
– their present topographic expression resulted
mainly from Cenozoic uplift and erosion
The Southern and Eastern
Continental Margins
• The Atlantic
Coastal Plain
and the Gulf
Coastal Plain
– form a
continuous belt
– from the
Northeastern
United States
to Texas
Coastal Plain Similarities
• Both areas have
– horizontal or gently seaward-dipping strata
– deposited mostly by streams flowing across them
• Seaward of the coastal plains
– lie the continental shelf, slope and rise,
– also areas of notable Mesozoic and Cenozoic
deposition
http://www.missgeo.com/directors
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Gulf Coast Sedimentation Pattern
• The overall Gulf Coast sedimentation pattern
– was established during the Jurassic
– and persists today
• Sediments derived from
• Cordillera
• western Appalachians
• Interior Lowlands
– were transported toward the Gulf of Mexico
– where they were deposited in terrestrial,
transitional, and marine environments
Gulf-Coastal-Plain Deposition
• Cenozoic Deposition on the Gulf Coastal Plain
– Depositional
provinces and
surface
geology
Showing
facies
changes
Cross
and
section of Eocene seaward
Claiborne Group thickening
Reservoirs for Hydrocarbons
• Many sedimentary rocks in the Gulf Coastal
Plain
– are either source rocks
– or reservoirs for hydrocarbons
http://www.spe.org/specma/binary/images/125
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