The Geology of the Paleozoic Era

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The Geology of the Paleozoic Era
7 of Earths history Permian Pennsylvanian Mis
sissippian Devonian Silurian Ordovician Cambrian
Boundaries are changes in the fossil record
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Base of the Cambrian system
Starts at appearance of first easily visible
fossils
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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.
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Paleozoic Overview

• Global tectonic theme of the Paleozoic - assembly
  of the supercontinent, Pangaea.
• 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.

Rifting raises water, moves plates, which later
collide, make foreland basins, water drops
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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

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Paleozoic Era key events
Transgression and Regressions
Extinctions
http//www.fmnh.helsinki.fi/users/haaramo/Meteor_I
mpacts/Middle_Paleozoic_impacts.htm
Rifting raises water, moves plates, which later
collide, make foreland basins, water drops
Assembly of Pangea
Deep
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
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Devonian Reconstruction High sea levels mostly
due large MORs and warm climates (no glaciers)
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How can we reconstruct past continent positions?

• Paleomagnetism Latitude
• Biogeography - Distribution of flora and fauna.
• Climatology - Climate sensitive sediments
• Tectonic Patterns continuation of mountains
• Cant use Magnetic Stripes on ocean floor- until
  200 mya Triassic\Jurassic and later

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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
Siberia - Russia (E of Urals), Part Asia
Kazakhstania - Kazakhstan China - All of SE
Asia and SE China Gondwana - S. continents, India

Six major Paleozoic continents are recognized
after Rodinia breakup Laurentia - North America,
Greenland, Scotland Rotated 90o Baltica - Russia
(W of Urals), Scandinavia
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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

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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
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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)
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http//www.geodynamics.no/Platemotions/500-400
M. Ordovician
Saucrorthis
Mostly distinct faunas Continents were not
close Note land at South Pole
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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.

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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.
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Oklahoma and Morocco Trilobites from the Devonian
Looks like Oklahoma was close to Morocco
Dalmanitidae
Reedops
Devonian Faunal Similarities CONTINENTS CLOSE
Dicranurus
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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

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Gondwana Laurasia collision Hercynian and
Allegheny Orogenies
Hercynian
North and South Europe suture Hercynian Orogeny
continuous w Allegheny Orogeny about 300 mya
Allegheny
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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.

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Paleogeography Late Permian
Hercynian N Eur-S Eur
Allegheny Orogeny
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Tectonic Details

• Thats the overview
• Now lets 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)
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Paleozoic Era key events
Next lets look closer at the Orogenies
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
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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.

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Global paleogeography for the Cambrian period
Avalonia Terranes
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Development of the Taconic Orogeny
Rodinia breaking up
Avalonia Terrane E. Cambrian
Plates reverse, in E. Ordovician
Africa moves toward both
Laurentia moves toward Avalonia
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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
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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.

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Cambrian paleogeography
Pre collisions Note equator
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Paleogeography N. Am. M Ord-Sil.
Post collisions
Queenston Clastic Wedge
Barrier Reefs Highstand Evaporites Lowstand
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Queenston clastic wedge
(Martinsburg Shale)
Hardyston Fm downfolded
(Allentown Dolo., Jacksonburg Ls.)
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The Caledonian Orogeny

• Baltica sutured onto Laurentia
• Mountains - Nova Scotia to Scandinavia
• Erosion resulted clastic wedge
• Devonian Old Red Sandstone
• Result called Laurasia

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Late Silurian - Early DevonianCaledonian
Orogeny-Laurasia forms
Caledonian Orogeny
Baltica sutured onto Laurentia
To our North
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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 gt Centerfield
  Reef
• Catskill delta as basin filled

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Early - Mid DevonianAcadian Orogeny-Laurasia
forms
Acadian Orogeny Southern Avalonia into Laurasia
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Accreted terranes (Does this remind you of
somewhere else?)
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Late Devonian paleogeography of North America
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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
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Catskill clastic wedge thickness
Coarse near source Wedge thins away
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Clastic Wedges fill Foreland Basins
Highlands source of sediment
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BIG Collision with Gondwana The Allegheny Orogeny

• 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

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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

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Allegheny and Ouachita Orogenies
Hercynian
Allegheny
Ouchita
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Antler Orogeny

• 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
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Late Devonian paleogeography of North America
Here it is
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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
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Pennsylvanian arkose, CO
Fountain Arkose, CO, deposited northeast of
Front Range Uplift
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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

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Paleozoic Era key events
Transgression and Regressions
Rifting raises water, moves plates, which later
collide, make foreland basins, water drops
Assembly of Pangea
High
Low
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
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Cambrian E Ord Sauk Sequence
Pre-collision, dramatic transgression due active
MORs Note extensive shallow carbonates and equator
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Time-transgressive Cambrian rocks Grand Canyon
Sauk Sequence
WEST
EAST
Transgression
Middle Cambrian
http//www.geo-tools.com/trilobites.htm
Lower Cambrian
http//www.wmrs.edu/projects/trilobites/images/tri
lo7-2.jpg
Note how western BAS is older than eastern BAS
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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
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Late Devonian Kaskasia Transgression
Carbonates over pure sands
Williston Basin surrounded by reefs Restricted
circulation caused evaporite precipitation
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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

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Paleozoic Era key events
Climate/Sedimentation
Rifting raises water, moves plates, which later
collide and fold. Folding makes deep basin. If
fold basin sediments, uplift.
Assembly of Pangea
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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

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Late Paleozoic Climates

• 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

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Glacial Abrasion in Bedrock
Source Tom Bean
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Pennsylvanian Glacier -Gondwana
Sea-level falls/rises as glaciers grow/melt
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Pennsylvanian Cyclothems
Rapid transgressions cover swamp as ice melts
Coal Swamp
swamp
estuary
Slow regression as ice sheet grows
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Coal formation Pennsylvania cyclothems
Highland source to east
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Pennsylvanian-age coal deposits
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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

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L. Permian Pangaea
Ice-free, dry interiors, no coal Much of land /-
30 degrees
Hot, dry climate Note evaporites
Pangaea is assembled, sea-level low
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PERMIAN N. America

• Inland sea limited to w Texas s NM
• Extensive evaporite deposits KS OK
• Redbeds over interior strong seasons