Chapter 21 The Geology of the Paleozoic Era

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Chapter 21The Geology of the Paleozoic Era
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The Paleozoic Era.

• Geologic periods in Paleozoic record 7 of
  Earths history
• Cambrian, Ordovician, Silurian, Devonian
  Carboniferous (Miss., Penn.) Permian
• Boundaries in the major divisions originally
  defined by changes in the fossil record
• Start of the Paleozoic used to be defined by
  appearance of first easily visible fossils later
  lowered to include small shelly fauna then
  lowered further to first appearance of complex
  branching trace fossils.

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Base of the Cambrian system
Trace fossil Phycodes pedum New modes of
locomotion
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Welsh Lower Paleozoic
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. Charles
Lapworth separated the Ordovician. Review Origin
of names
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Paleozoic Overview

• Global tectonic theme of the Paleozoic - assembly
  of the supercontinent, Pangaea.
• Deposition due to transgressions (and
  disconformities due regressions) of shallow
  continental (epeiric) seas. Interiors of
  continents were frequently flooded.
• Formation of mountain belts at edges
• tectonic activities associated with the assembly
  of Pangaea.

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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.
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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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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Paleogeographic Reconstructions and Maps

• Geologists want to create maps of the Earth as it
  was in the past,
• correctly position the continents for different
  time periods, and
• reconstruct geography on the continents.

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What data are used to do this as accurately as
possible?

• Paleomagnetism Latitude
• Biogeography - Distribution of flora and fauna.
• Climatology - Climate sensitive sediments
• Tectonic Patterns continuation of mountains
• Cant use Magnetic Stripes on ocean floor-
  Mesozoic 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
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, rotated 30o
Gondwana moved 40o S to a South Pole location
(Late Ord. tillites)
Remember Hawaiians And Emperor Chain Evidence of
changing directions Varying rifting pushes
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http//www.geodynamics.no/Platemotions/500-400
M. Ordovician
http//www.gl.rhbnc.ac.uk/seasia/Biogeog_pdfs/Fort
ey_Cocks.pdf
Saucrorthis
Mostly distinct faunas Continents were not close
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Devonian

• Acadian Orogeny in the Appalachian
• 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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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.
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
Dicranurus
Devonian Faunal Similarities
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Final Assembly of Pangea

• Laurasia collides with Gondwana to form Hercynian
  Mts. Late Paleozoic forms Europe
• Pennsylvanian Siberia collided with
  Kazakhstania, forming Altai Mts.
• Permian Kazakhstania collided with Baltica,
  forming the Urals
• Single continent surrounded by Panthalassa Ocean
  w Tethys Sea

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Gondwana Laurasia collision Hercynian orogeny
North and South Europe suture Hercynian Orogeny
continuous w Allegheny Orogeny about 300 mya
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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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Paleozoic Era key events
Next lets look closer at the Orogenies
Rifting raises water, moves plates, which later
collide.
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, about 500 mya, the direction
  of plate motion reversed and Iapetus began to
  close.

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Global paleogeography for the Cambrian period
Terranes
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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.

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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 Dm., 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
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 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 push stopped and 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 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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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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Appalachian Provinces

• Piedmont Province at collision suture, very
  metamorphosed and intruded
• Blue Ridge Grenvillian rocks thrust cratonward.
• 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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Physiographic provinces Appalachians
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Ouachita Orogeny

• Also Late Paleozoic Gondwana collision
• Northern edge S. America and S. Laurasia
• Smaller plates between them crushed
• Deepwater sediments thrust over Laurasia forming
  long fold and thrust mountain belt
• Similar to Appalachian Valley and Ridge

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Allegheny and Ouachita Orogenies
Hercynian
Allegheny
Ouchita
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Western North America

• In the Devonian, a westward dipping subduction
  zone formed off Western Laurasia.
• An Island Arc formed, the Klamath Arc
• The ocean floor between subducted as the arc
  approached and collided with the continent
• Late Devonian to Early Mississippian
• Called the Antler Orogeny, basin thrust East
• Klamath Mts. and North Sierra Nevada

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Antler Orogeny
Antler Mts. are folded basin sediments
Beginning of Cordillera Construction, Devonian to
Mississippian
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Late Devonian paleogeography of North America
Here it is
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Paleozoic structure of the West
Late Paleozoic also saw the beginnings of the
Rockies
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The Ancestral 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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Paleozoic structure of the West
Exposed granite eroded as arkoses (feldspar rich
sandstones)
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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 and fold. Folding makes deep basin. If
fold basin sediments, uplift.
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 no 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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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)
• 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

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Next Time

• A survey of Paleozoic Life, and
• Latest Permian Mass Extinction
• Most profound in history of life.