late paleozoic climates, paleogeography, distinctive...

Earth History, Ch. 15 1

Today’s agenda

• Late Paleozoic climates, paleogeography,

distinctive sedimentary deposits and

mountain building


Late Paleozoic paleogeography

and climate (1)

• Mississippian:

– Minor glaciation in Southern Hemisphere

– Crinoidal limestone deposition in the tropics

– Early development of coal swamps

– Gondwanaland, Euramerica, and Siberia are

approaching one another—the beginnings of

supercontinent Pangaea


Euramerica

Gondwanaland

Siberia

Devonian

Euramerica

Gondwanaland

Siberia


Euramerica

Gondwanaland

Siberia

Mississippian

Deposition of crinoidal

limestone in tropical seas



and climate (2)

• Pennsylvanian to Early Permian:

– Increase in latitudinal climate gradient

• “Icehouse world”

• Full-scale coal swamps in tropics

• Collision of Gondwanaland and Euramerica

– Hercynian/Alleghenian Orogeny (final pulse of

Appalachian mountain building)


Euramerica

Gondwanaland

Siberia

Pennsylvanian

Paleotethys Ocean

Ural Mountains

Great coal deposits in

tropical coastal areas

Early Pangaea

Earth History, Ch. 15 7 Early Permian

Paleotethys Ocean

Tethys Ocean

Seasonal climate in

continental interiors

Pangaea



and climate (3)

• Late Permian: Nearly complete assembly

of Pangaea

– Siberia joined to eastern Europe along Ural

Mountains

– Southeast Asia only remaining isolated

landmass

• Huge Pangaea landmass and new mountain

belts caused strong seasonality of climates

Earth History, Ch. 15 9 Late Permian

Paleotethys Ocean

Tethys Ocean

Pangaea


Midcontinent “cyclothems”

• Pennsylvanian was a time of glacial

advances and retreats in Gondwanaland

– Result was cyclical rise and fall of global sea

level: deposition of “cyclothems”

– 20,000 yr to 400,000 yr cycles; up to 100 m

fluctuations in sea level


Pennsylvanian

midcontinent

seaway

southern glaciers


shoreline at

highstand

shoreline at

lowstand


Midcontinent cyclothems


Midcontinent

cyclothems


Permian Basin of west Texas &

New Mexico

• “Permian Basin complex” includes Glass Mountains, Delaware Basin, and Guadalupe Mountains

– Foreland basin located north of Marathon fold belt

– Permian reef system is one of world’s largest, best known fossil reefs

– One of largest oil-producing regions in United States


Permian

Basin


Permian reef complex

• Reef development began in Middle Permian time

• Reef community included calcareous sponges, algae, bryozoans—with aragonite cement

• Reef growth was very rapid

– Reef crest rose 600m (2000 ft) above adjacent sea floor of Delaware Basin

• Demise of reef occurred in Late Permian time when Delaware Basin dried out and was filled with evaporite deposits


Permian reef complex


Permian Basin


Euramerica

Gondwanaland

Siberia

Pennsylvanian

Paleotethys Ocean

Ural Mountains

Early Pangaea


Allegheny orogeny

• Pennsylvanian collision of Gondwanaland with

Euramerica caused third episode of orogeny

along eastern margin of Euramerica

– Present-day Appalachian Mountains (“Valley and

Ridge province”)

– Ouachita-Marathon foldbelt of Arkansas, Oklahoma

and Texas

– Another episode of clastic wedge deposition in the

foreland basin


Alleghenian

Orogeny

Three pulses:

Alleghenian

Acadian

Taconic


Ouachita/Marathon foldbelt

• Continuation of Allegheny deformation

extended down and across Alabama,

Mississippi into Arkansas, Oklahoma,

and Texas

– Ouachita Mountains (Arkansas and Oklahoma)

– Marathon Mountains (west Texas)


Ouachita-Marathon foldbelt


Ancestral Rocky Mountains

• Also in Pennsylvanian time:

– Front Range and Uncompahgre uplifts

created ancestral Rocky Mountains

– Vertical uplift of Precambrian ingeous and

metamorphic rocks!!

• Erosion of these uplifts produced thick alluvial fan

deposits of coarse-grained sandstones (arkose)—

the present-day “flat irons”



granitic crust

sedimentary veneer



alluvial fan deposits



Front Range uplift Uncompahgre uplift


Western U.S.—continental

accretion

• Island arc system continued to exist off

western margin of Euramerica (Pangaea)

– Continuation of Antler-type orogeny

• During late Permian time, several small

plates accreted to continental margin

– Exotic terranes from California to Alaska

– Exotic fossil assemblages (resemble distinctive

ones known elsewhere from SE Asia)


Western U.S.—accretion


Global tectonic summary

Steps in the development of

supercontinent Pangaea


Late Proterozoic 600 Ma

Siberia


Latest Proterozoic 560 Ma

Siberia

Laurentia

Baltica


Early Cambrian 540 Ma

Siberia Laurentia

Baltica


Late Cambrian 500 Ma

Siberia Laurentia

Baltica


Middle Ordovician 470 Ma

Siberia

Laurentia

Baltica Taconic arc


Silurian 430 Ma

Acadian orogeny

Siberia


Early Devonian 400 Ma

Euramerica

Gondwanaland

Siberia


Late Devonian 370 Ma

Euramerica

Gondwanaland

Antler

orogeny

Siberia


Mississippian 340 Ma

Euramerica

Gondwanaland

Onset of Late Paleozoic ice age

Siberia


Pennsylvanian 300 Ma

early Urals


Early Permian 280 Ma

Paleotethys

Tethys

Pangaea


Late Permian 260 Ma

Paleotethys

Tethys

Pangaea

late paleozoic climates, paleogeography, distinctive...

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