Cenozoic History

transcript

• 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 History

• In this class we use – the term Tertiary

Period – rather than

Paleogene and Neogene Periods

Cenozoic Time Scale

Late CretaceousRifts separate Africa and South America and then India, Australia, Antarctica. North America rifts from Europe.

Old Gondwana (Africa, India, Australia) move north toward Eurasia, closing the Tethys Ocean and forming the Alpine-Himalayan mountains.

The Atlantic lengthens / widens, the Sevier orogeny continues, and the Caribbean arc forms.

Texas 65-144 Ma: continuing shallow limestone and shale deposition to the southeast (from Rockies).

http://vishnu.glg.nau.edu/rcb/globaltext.html

Paleocene / Eocene

Himalayan Orogeny. Alps and Pyrenees form.

The modern patterns of geography appear.

Atlantic continues to open. Rocky Mountains grow.

Texas 65 - 35 Ma: shale and sandstone in southeast region prograde shoreline (from the Rockies). Volcanic activity in Panhandle.http://vishnu.glg.nau.edu/rcb/globaltext.html

• By Eocene time, – the Americas had completely separated – from Europe and Africa– but India had not yet collided with Eurasia

Cenozoic Plate Tectonics

Oligocene and Miocene

Orogeny continues inthe Mediterranean region and India nears its junction with southern Asia.

Antarctica isolated.

Southwestern North America intercepts the East Pacific Rise and a great extensional event, the Basin and Range orogeny begins.

Texas 35-5 Ma: continued sandstone/shale deposition and progradation of shoreline (erosion of Rockies)

• During Miocene time, – the Atlantic Ocean basin continued to

widen– and India had collided with Eurasia

• The Tethys Sea between Africa and Eurasia – was mostly closed by this time

Cenozoic Plate Tectonics

Age of Ocean Basins

• A triple junction – joins the East African

Rift System – to the Gulf of Aden – and the Red Sea– Oceanic crust began

forming • in the Gulf of Aden

about 10 million years ago

– Red Sea rifting began later and oceanic crust is now forming

East African Rift

• Circum-Pacific orogenic belt and the Alpine-Himalayan orogenic belt are the sites of most recent geologic and orogenic activity

Orogenic Belts

• Remember that during Mesozoic time – the Tethys Sea separated much of Gondwana – from Eurasia

• Closure of this sea – took place during the Cenozoic – as the African and Indian plates – collided with the huge landmass to the north

Closure of the Tethys Sea

• Eocene timeCenozoic Plate Tectonics

• Miocene timeCenozoic Plate Tectonics

• 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

The Himalayas

• Oceanic lithosphere – subducted beneath southern Tibet – as India approached Asianorthern margin of India

Before India Collided with Asia

southern margin of Tibet

• About 40 to 50 million years ago• India collided with Asia,

– but because India was to light to subduct, – it thrust under Asia

India Collided with Asia

• Thrusting of Asian rocks – onto the Indian subcontinent – accompanied continued convergence

Continued Convergence

• Since about 10 million years ago, – India has moved beneath Asia – along the main boundary fault

India Moved beneath Asia

– 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

• 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

• Deformation, volcanism and plutonism continued

• 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

The North American Cordillera

• North American Cordillera – and the

major provinces

– of the United States and Canada

Cordillera

• Locations of Proterozoic sedimentary Basins – in the western United

States and Canada• Belt Basin• Uinta Basin• Apache Basin

Sedimentary Basins in the

Cordilleran Mobile Belt

Antler Orogeny in Devonian

• 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– ???

Cordillera Evolved

Plate Interactions Continue

http://earth.geol.ksu.edu/sgao/research/data/

seiswus/example1.gif

• 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

The 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

Laramide orogeny

• 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

Change to Shallow Subduction

• With nearly horizontal subduction, – igneous activity ceased – and the continental crust – was deformed mostly by vertical uplift

Igneous Activity Ceased

• Disruption of the oceanic plate – by the mantle plume– marked the onset – of renewed igneous activity

Renewed Igneous Activity

• The vast batholiths in • Idaho • British Columbia• Sierra Nevada of California

– were emplaced during the Mesozoic Era

– intrusive activity continued into Tertiary

Cordilleran Igneous Activity

http://www.bhc.edu/academics/science/harwoodr/GEOL102/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

– 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

Columbia River Basalts

~ 20 lava flows of the Columbia River basalts exposed in the canyon of the

Grand Ronde River in Washington

• 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

Cascade Range

http://www.cr.nps.gov/history/online_books/resedu/resedu2a.htm

Basin and Range

• Generalized cross section of the Basin and Range Province– ranges are bounded by faults

Basin and Range Province

Colorado Plateau

– Paleozoic rocks exposed in the Grand Canyon, Arizona

Colorado Plateau

– Mesozoic sedimentary rocks in the Valley of the Gods, Utah

Colorado Plateau– Mesozoic sedimentary rocks at Colorado

National Monument, Colorado

• 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

Pacific Coast

• 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

Change from Subduction

• 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

Extending the San Andreas Fault

• A vast area called the Interior Lowlands

– the Great Plains

– and the Central Lowlands

The Continental Interior

• Deformation in the Appalachians has a long history– began during the Late Proterozoic

Cenozoic History of the Appalachian Mountains

– during Late Triassic time, the entire region experienced faulting as Pangaea fragmented

• By the end of the Mesozoic– erosion had reduced the mountains to a

plain across which streams flowed eastward to the ocean

Reduced to Plains

• Streams developed across the plains during the Tertiary

Appalachians in the Tertiary

• Although these mountains have a long history – their present topographic expression resulted

mainly from Cenozoic uplift and erosion

Present Appalachian Topography

• The Atlantic Coastal Plain and the Gulf Coastal Plain – form a

continuous belt

– from the Northeastern United States to Texas

The Southern and Eastern Continental Margins

• 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

Coastal Plain Similarities

http://www.missgeo.com/directors%20-%20mail.htm

• 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 Coast Sedimentation Pattern

• Cenozoic Deposition on the Gulf Coastal Plain

Gulf-Coastal-Plain Deposition

– Depositional provinces and surface geology

Cross section of Eocene Claiborne Group

Showing facies changes and seaward thickening

• Many sedimentary rocks in the Gulf Coastal Plain – are either source rocks – or reservoirs for hydrocarbons

Reservoirs for Hydrocarbons

http://www.spe.org/specma/binary/images/1257473world_oil_production.gif

Cenozoic History

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