7% of Earth’s history
The Geology of the
Paleozoic Era
Permian
Pennsylvanian
Mississippian
Devonian
Silurian
Ordovician
Cambrian
Boundaries are changes in the fossil record
Base of the Cambrian system
Starts at appearance of first easily visible fossils
Boundaries changes in fossils
Prof Adam Sedgwick (Cambridge) studied the
Cambrian (including the Ordovician) based on
superposition and structural geology.
Roderick Murchison described and mapped the
Silurian based on fossils. Together they defined
the Devonian System in Devon and Cornwall.
Murchison established the Permian in Russian,
then returned and split up Cambrian based on
fossils. Later Charles Lapworth separated out the
Ordovician.
Paleozoic Overview
• Global tectonic theme of the Paleozoic assembly of the supercontinent, Pangaea.
Rifting raises water, moves plates, which later collide, make foreland basins, water drops
• Deposition due to transgressions, and erosion disconformities due to regressions.
• Transgressions caused shallow continental
(epeiric) seas. Interiors of continents were
frequently flooded.
• Formation of mountain belts at edges: collisions
with small and large landmasses
• Collisions resulted in assembly of Pangaea.
Paleozoic Global Geology
• Six major Paleozoic continents are
recognized after Rodinia breakup
• Gondwana - S. continents, India
• Laurentia - North America, Greenland,
part Gr. Britain
• Baltica – Northern Europe
• Siberia – Most of Northern Asia
• Kazakhstania – part Central Asia
• China - All of SE Asia and SE China
Transgression and Regressions
Extinctions:
Paleozoic Era key events
http://www.fmnh.helsinki.fi/users/haaramo/Meteor_Impacts/Middle_Paleozoic_impacts.htm
Rifting raises water, moves plates, which later collide, make foreland basins, water drops
Assembly of
Deep
Pangea
Mass Extinction
Gondwana/Laurasia
Catskill Clastic Wedge
Continues subduction Iapetus ; South docks w/ rest of Avalonia
Old Red SS
Iapetus floor subducted ,
Laurentia and Baltica collide - Laurasia
Avalonia collides with Laurentia
Notice: 3 orogenies, 4 transgressions, 2 glaciations,
1 huge mass extinction
Devonian Reconstruction
High sea levels mostly due large MORs
and warm climates (no glaciers)
How can we reconstruct past
continent positions?
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Paleomagnetism Latitude
Biogeography - Distribution of flora and fauna.
Climatology - Climate sensitive sediments
Tectonic Patterns – continuation of mountains
Can’t use Magnetic Stripes on ocean floor- until
200 mya Triassic\Jurassic and later
Global paleogeography for the
Cambrian period
All six continents occur at low paleolatitudes
Ocean waters circulate freely/ poles appear ice-free
Epeiric seas cover much of continents except Gondwana
Highlands in N Gondwana, Eastern Siberia, Central Kazakhistan
NOTE:
Six major Paleozoic continents are recognized after Rodinia breakup
Laurentia - North America, Greenland, Scotland Rotated 90o
Baltica - Russia (W of Urals), Scandinavia
Siberia - Russia (E of Urals), Part Asia
Kazakhstania - Kazakhstan
China - All of SE Asia and SE China
Gondwana - S. continents, India
Ordovician - Silurian
SILURIAN
– Silurian collision of Baltica/Laurentia
Caledonian Orogeny, suturing forms Laurasia
----------------------------------ORDOVICIAN
– Ordovician Gondwana moved 40o S to a South Pole
location (Glaciers formed, we find L. Ord. tillites)
– Baltica moved S, then N
– Microcontinent & Island Arcs collided with Laurentia
(led to Taconic Orogeny) narrowing Iapetus
How do we know?
L. Ordovician biogeography of Carolinites genacinaca
Confirms paleomagnetic latitudes
From McCormick & Fortey 1999.
J. Paleontol. 73(2):202-18.)
Trilobite Paleogeography
Global paleogeography
Mid Ordovician to Silurian
Siberia moved from equatorial
to northern temperate latitudes
Small piece of
Avalonia hits in
Ordovician
Baltica moved S, then N
and collided with Laurentia. Note rotated 30o
Gondwana moved 40o S to a
South Pole location (Late Ord. tillites)
http://www.geodynamics.no/Platemotions/500-400
M. Ordovician
Saucrorthis
Mostly distinct faunas
Continents were not close
Note land at South Pole
Devonian
– Acadian Orogeny in the Appalachians
– Other orogenies: Antler (W. N.Am. Cordillera)
and Ellesmere (north margin of Laurentia)
– Gondwana moves to higher southern
latitudes. All other continents at low northern
latitudes.
Paleogeography Early Devonian
Continued collision of Baltica/Laurentia formed Laurasia, closed Iapetus Ocean
Caledonian Orogeny in B/L finishes E. Dev
Acadian Orogeny in the Appalachians
folds older rocks M. Dev.
Antler
Caledonian
Acadian
Other orogenies: Antler (Cordillera) and Ellesmere (north margin of Laurentia)
Gondwana moves to higher southern latitudes.
All other continents at low northern latitudes.
Oklahoma and Morocco Trilobites from the Devonian
Looks like Oklahoma was close to Morocco
Dalmanitidae
Reedops
Devonian Faunal Similarities: CONTINENTS CLOSE
Dicranurus
Final Assembly of Pangea
• Permian – Kazakhstania collided with Baltica,
forming the Urals
• Single continent surrounded by Panthalassa
Ocean w Tethys Sea
________________________________________
• Pennsylvanian – Siberia collided with
Kazakhstania, forming Altai Mts.
• Laurasia collides with Gondwana to reform
Appalachians and to form Hercynian Mts. in Late
Paleozoic. Hercynian collision forms Europe
Gondwana – Laurasia collision
Hercynian and Allegheny Orogenies
Hercynian
Allegheny
North and South Europe suture
Hercynian Orogeny continuous w Allegheny
Orogeny about 300 mya
Final Assembly of Pangaea
• After the suturing of Gondwana and Laurasia
(includes Hercynian and Allegheny Orogenies),
• Then:
• Siberia collided with Kazakhstania in the
Pennsylvanian, forming the Altai Mountains.
• Kazakhstania collided with Baltica in the
Permian, forming the Ural Mountains.
Paleogeography Late Permian
Allegheny Orogeny
Hercynian
N Eur-S Eur
Tectonic Details
• That’s the overview
• Now let’s look in more
detail at the collision,
i.e. orogenies
Angular Unconformity between Martinsburg Fm (mid-Ordovician,
folded by Taconic) and overlying Shawangunk Fm (Silurian,
folded by Acadian and Allegheny Orogenies)
Next let’s look closer at the Orogenies
Paleozoic Era key events
Rifting raises water, moves plates, which later collide, make foreland basins, water drops
Assembly of
Pangea
Gondwana/Laurasia
Catskill Clastic Wedge
Continues subd Iapetus South docks rest Avalonia
Old Red SS
Iapetus floor subducted Scotl Scan NE Can
Lauentia and Baltica collide - Laurasia
Avalonia collides with Laurentia
Tectonics Paleozoic North America
• In the Cambrian, several small terranes
lay to the south of Laurentia as it
separated from Baltica. The shores were
passive margins.
• In the Ordovician, beginning about 500
mya, the direction of plate motion reversed
and Iapetus began to close.
Global paleogeography for the
Cambrian period
Avalonia Terranes
Development of the Taconic Orogeny
Rodinia breaking up
Avalonia Terrane E. Cambrian
Plates reverse, in E. Ordovician
Laurentia moves toward Avalonia
Africa moves toward both
Taconic orogeny (cont)
Mid – L. Ordovician, N.Avalonia
and an island arc dock with
Laurentia, beginning the
Appalachians
Rocks thrust up over margin of Laurentia
Interior of Laurentia, Ord.-Silurian
• Inland, the Taconic collisions caused the
crust to be warped down, forming the
Appalachian FORELAND BASIN
• Deep water sediments were deposited in
the basin, until sediments eroded from the
Taconic mountains filled the basin, and
shallow water deposits prevailed.
• The Queenston Clastic Wedge filled the
foreland basin. We saw the Shawangunk
and High Falls – Bloomsburg Formations
at the Delaware Water Gap.
Cambrian paleogeography
Pre –collisions
Note equator
Paleogeography N. Am. M Ord-Sil.
Post collisions
Barrier Reefs Highstand
Evaporites Lowstand
Queenston Clastic Wedge
Queenston clastic wedge
Hardyston Fm
(Allentown Dolo., Jacksonburg Ls.)
downfolded
(Martinsburg Shale)
The Caledonian Orogeny
• Baltica sutured onto Laurentia
– Mountains - Nova Scotia to Scandinavia
– Erosion resulted clastic wedge
– Devonian Old Red Sandstone
• Result called Laurasia
Late Silurian - Early Devonian
Caledonian Orogeny-Laurasia forms
Caledonian Orogeny
To our North
Baltica sutured onto Laurentia
The Acadian Orogeny
• Continued subduction of Iapetus ocean floor
in Devonian
• Additional parts of Avalonia docked with Laurentia
– Re-folding of Old Mountains – Virginia to Maritimes
– Old rocks even more folded and metamorphosed
– Erosion resulted in Catskill clastic wedge
– Facies change in foreland basin – shallow marine to
streams in Middle Devonian as basin fills
– Field trip Marcellus to Mahantango => Centerfield Reef
– Catskill delta as basin filled
Early - Mid Devonian
Acadian Orogeny-Laurasia forms
Acadian Orogeny
Southern Avalonia into Laurasia
Accreted terranes
(Does this remind you of somewhere else?)
Late Devonian paleogeography
of North America
Catskill Formation
Clastic Wedge from Acadian
collision w rest of Avalonia
E-Mid Devonian docking,
folding.
By L. Dev. filled, mostly stream
deposits, floodplains have
fossils of land plants and
amphibians
Oxidation state of Iron
depended on oxygen
levels
Catskill clastic wedge thickness
Coarse near source
Wedge thins away
Clastic Wedges fill Foreland Basins
Highlands source of
sediment
BIG Collision with Gondwana
The Allegheny Orogeny
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•
Initial contact Late Mississippian
Northwest Africa collided
Folding of Pennsylvanian rocks proves long duration
Deformation much more extensive than the Taconic or
Acadian – New York to Alabama
Physiographic provinces
Appalachians
• Piedmont Province: at collision suture, very metamorphosed and
intruded
• Blue Ridge: Grenvillian rocks thrust toward craton.
• Valley and Ridge: northwest thrust faults and northeast anticlines
and synclines
Thin-skinned tectonics platform rx folded more than basement.
Resistant Ridges
• Plateau: little deformation
Allegheny and Ouachita Orogenies
Hercynian
Allegheny
Ouchita
Antler Orogeny
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•
In the Devonian, a westward dipping subduction zone formed off Western
Laurasia.An Island Arc formed, the Klamath Arc,ocean floor subducted as the arc
approached and collided with the continent
Late Devonian to Early Mississippian,
Basin thrust East
Klamath Mts. and North Sierra Nevada
Antler Mts. are folded basin sediments, Devonian and Mississippian
This is the beginning of Cordillera Construction
Late Devonian paleogeography
of North America
Here it is
Paleozoic structure of the West
Exposed granite eroded as arkoses
(feldspar rich sandstones)
Late Paleozoic also saw the
beginnings of the Rockies
Devonian – Ouachita Orogeny creates compressional
stress
Pennsylvanian – blocks push up along high angle
faults, relieving the stress. PreCambrian basement
exposed.
Resulted in Front Range Uplift CO & WY
Uncompahgre Uplift CO & NM
Pennsylvanian arkose, CO
Fountain Arkose, CO, deposited
northeast of Front Range Uplift
Next: Cratonic Sequences
• Laurence Sloss: Major transgressive-regressive
cycles
• 4 in Paleozoic
• Allow long range correlation “Sequence Stratigraphy”
• Transgression: nearshore sand covered by
muds and/or carbonates
• Regression:
– Nearshore: erosion and disconformity
– Far offshore: sediments coarsening upward
Transgression and Regressions
Paleozoic Era key events
Rifting raises water, moves plates, which later collide, make foreland basins, water drops
Assembly of
Pangea
Low
High
ABS: Sea level rise (cyclic) due Gondwana glaciation Penn-Pm regression due
slowdown spreading, assembly of Pangaea, drained continent L Pm
KS: filling in of the Appalachian foreland basin by Late Devonian time
TC: glacial melting and accelerated sea-floor spreading
Sauk: High rates of sea-floor spreading
Cambrian – E Ord Sauk Sequence
Pre-collision, dramatic transgression due active MORs
Note extensive shallow carbonates and equator
Time-transgressive Cambrian
rocks Grand Canyon
Sauk Sequence
WEST
Transgression
Middle
Cambrian
http://www.geo-tools.com/trilobites.htm
Lower
Cambrian
http://www.wmrs.edu/projects/trilobites/images/trilo7-2.jpg
Note how western BAS is older than eastern BAS
EAST
Tippecanoe Transgression M Ord-Sil.
Reworking of Sauk sands gives pure sands
useful in glass manufacture.
Sands covered by carbonates
as transgression advances
Michigan Basin surrounded by reefs
Restricted circulation caused
evaporite precipitation
Source of Rock Salt
About 5 smaller T-R Pulses
Late Devonian Kaskasia
Transgression
Carbonates over pure sands
Williston Basin surrounded by reefs
Restricted circulation caused
evaporite precipitation
Absoroka Sequence
• Transgression starts M Pennsylvanian
• Regression starts L Pennsylvanian
• Cyclothems Reflect Glacial sea-level var.
PERMIAN
• Inland sea limited to w Texas & s NM
• Extensive evaporite deposits KS – OK
• Redbeds over interior
Climate/Sedimentation
Paleozoic Era key events
Rifting raises water, moves plates, which later collide and fold. Folding makes deep basin. If fold basin sediments, uplift.
Assembly of
Pangea
Next: Paleozoic Climates
•
Paleozoic mostly warm, but two glacial times,
Ordovician and Pennsylvanian to Late Permian.
•
Cool Middle Ordovician
– CO2 tied up in carbonates – less greenhouse
– Extensive Gondwana tillites and striations
– Sea level retreats as glacier holds water
Late Paleozoic Climates
(1) Cool Pennsylvanian – M Permian
– CO2 tied up in carbonates
– Extensive Gondwana tillites and
striations – sea-level fluctuations due
glacial (slow regression) and
interglacial (fast melt) “cyclothems”
– Generated Coal deposits, carbon reservoirs,
low CO2
Glacial Abrasion in Bedrock
Source: Tom Bean
Pennsylvanian Glacier -Gondwana
Sea-level falls/rises as glaciers grow/melt
Pennsylvanian Cyclothems
Rapid transgressions
cover swamp as ice
melts
Coal Swamp
swamp
estuary
Slow regression as
ice sheet grows
Coal formation Pennsylvania cyclothems
Highland
source to
east
Pennsylvanian-age coal deposits
Late Paleozoic Climates - 2
(2) The Late Permian WARM
• Pangaea was ice-free
• Warm equatorial waters from the Panthalassa
Ocean reached both poles.
• No glaciers = no coal (need rapid transgression
due glacial melting)
• The Gondwana landmass had drifted north into
warmer climates.
• reduced coal formation caused carbon dioxide
levels to rise
• Greenhouse effect
L. Permian Pangaea
Ice-free, dry interiors, no coal
Much of land +/- 30 degrees
Pangaea is assembled, sea-level low
Hot, dry climate
Note evaporites
PERMIAN N. America
• Inland sea limited to w Texas & s NM
• Extensive evaporite deposits KS – OK
• Redbeds over interior – strong seasons