late paleozoic climates, paleogeography, distinctive...

Earth History, Ch. 15 1

Today’s agenda

• Late Paleozoic climates, paleogeography,

distinctive sedimentary deposits and

mountain building

Earth History, Ch. 15 2

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

Earth History, Ch. 15 3

Euramerica

Gondwanaland

Siberia

Devonian

Euramerica

Gondwanaland

Siberia

Earth History, Ch. 15 4

Euramerica

Gondwanaland

Siberia

Mississippian

Deposition of crinoidal

limestone in tropical seas

Earth History, Ch. 15 5

Late Paleozoic paleogeography

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)

Earth History, Ch. 15 6

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

Earth History, Ch. 15 8

Late Paleozoic paleogeography

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

Earth History, Ch. 15 10

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

Earth History, Ch. 15 11

Pennsylvanian

midcontinent

seaway

southern glaciers

Earth History, Ch. 15 12

shoreline at

highstand

shoreline at

lowstand

Earth History, Ch. 15 13

Midcontinent cyclothems

Earth History, Ch. 15 14

Midcontinent

cyclothems

Earth History, Ch. 15 15

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

Earth History, Ch. 15 16

Permian

Basin

Earth History, Ch. 15 17

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

Earth History, Ch. 15 18

Permian reef complex

Earth History, Ch. 15 19

Permian Basin

Earth History, Ch. 15 20

Euramerica

Gondwanaland

Siberia

Pennsylvanian

Paleotethys Ocean

Ural Mountains

Early Pangaea

Earth History, Ch. 15 21

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

Earth History, Ch. 15 22

Earth History, Ch. 15 23

Alleghenian

Orogeny

Three pulses:

Alleghenian

Acadian

Taconic

Earth History, Ch. 15 24

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)

Earth History, Ch. 15 25

Ouachita-Marathon foldbelt

Earth History, Ch. 15 26

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”

Earth History, Ch. 15 27

Ancestral Rocky Mountains

Earth History, Ch. 15 28

Ancestral Rocky Mountains

granitic crust

sedimentary veneer

Earth History, Ch. 15 29

Ancestral Rocky Mountains

alluvial fan deposits

Earth History, Ch. 15 30

Ancestral Rocky Mountains

Front Range uplift Uncompahgre uplift

Earth History, Ch. 15 31

Earth History, Ch. 15 32

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)

Earth History, Ch. 15 33

Western U.S.—accretion

Earth History, Ch. 15 34

Global tectonic summary

Steps in the development of

supercontinent Pangaea

Earth History, Ch. 15 35

Late Proterozoic 600 Ma

Siberia

Earth History, Ch. 15 36

Latest Proterozoic 560 Ma

Siberia

Laurentia

Baltica

Earth History, Ch. 15 37

Early Cambrian 540 Ma

Siberia Laurentia

Baltica

Earth History, Ch. 15 38

Late Cambrian 500 Ma

Siberia Laurentia

Baltica

Earth History, Ch. 15 39

Middle Ordovician 470 Ma

Siberia

Laurentia

Baltica Taconic arc

Earth History, Ch. 15 40

Silurian 430 Ma

Acadian orogeny

Siberia

Earth History, Ch. 15 41

Early Devonian 400 Ma

Euramerica

Gondwanaland

Siberia

Earth History, Ch. 15 42

Late Devonian 370 Ma

Euramerica

Gondwanaland

Antler

orogeny

Siberia

Earth History, Ch. 15 43

Mississippian 340 Ma

Euramerica

Gondwanaland

Onset of Late Paleozoic ice age

Siberia

Earth History, Ch. 15 44

Pennsylvanian 300 Ma

early Urals

Earth History, Ch. 15 45

Early Permian 280 Ma

Paleotethys

Tethys

Pangaea

Earth History, Ch. 15 46

Late Permian 260 Ma

Paleotethys

Tethys

Pangaea