THE EARLY PALEOZOIC
THE CAMBRIAN 544-505 MY
CAMBRIA>>WALES
ADAM SEDGWICK 1835
THE ORDOVICIAN 505-438 MY
ORDOVICE>>WELSH TRIBE
CHARLES LAPWORTH 1879
NEOPROTEROZOIC TO
MIDDLE CAMBRIAN
STRATIGRAPHIC COLUMN.
PRINCIPLE LIFE FORMS
AND STAGES OF THE
EARLY CAMBRIAN
PLACEMENT OF
BOUNDARY AT THE
PHYCODES pedum ZONE,
TRACE FOSSIL, @ 544 MY
TYPE LOCALITY>>BURIN
PENINSULA,
NEWFOUNDLAND
CAMBRIAN DIVISIONS
BASED TRILOBITE ZONES
[BIOMERES -INTERVALS
OF TIMES BETWEEN
TRILOBITE EXTINCTIONS]
PALEOGEOGRAPHY
• CAMBRIAN CONTINENTS WITHIN 60O OF
PALEOEQUATOR
• GONDWANA
– TIBET, SE ASIA, ARABIA, AFRICA, AUSTRALIA,
ANTARCTICA, S. AMERICA
• LAURENTIA> RIFT ZONES>PASSIVE
MARGINS
• FLOODING OF INTERIORS DUE TO RIFT
SYSTEMS
• IAPETUS OPENED BET N. AMERICA &
EUROPE
• SUBDUCTION ZONES DEVELOPED LATER
TECTONIC EVENTS
 Pan-African Orogeny
 Caledonian-Hercynian Orogeny
 Appalachian, Caledonian, Hercynian, Urals, Ouachita,
Samfrau
 Overall scenario is coalescence of Pangea during
most of the Paleozoic





Taconic Orogeny mid to late Ordovician
Caledonian Orogeny late Silurian to early Devonian
Acadian Orogeny mid Devonian
Alleghenian Orogeny late Penn, Permian
Hercynian Orogeny - Ouachita Orogeny
PLATE TECTONIC
MOVEMENTS FROM
THE
NEOPROTEROZOIC
TO THE DEVONIAN
(750 MY TO 370MY)
BREAK UP OF RODINIA
AVALONIAN OROGENY
OPENING OF IAPETUS
OPENING OF RHEIC
TACONIC OROGENY
CLOSING OF IAPETUS
ACADIAN OROGENY
The Appalachians
• Valley and Ridge
– folded & faulted sedimentary rks
• Blue Ridge Province
– metamorphosed Precambrian and Paleozoic
Rks
• Inner Piedmont
– high grade metamorphic rks intruded by
granites
• Charlotte & Carolina Slate Belt
– metamorphosed & folded late Proterozoic &
Cambrian sediments and volcanics
A) Cambro-Ordovician Passive Margin: Sandy Shelf Deposits
B) Middle to Late Ordovician Development of Trench Along the Eastern
Boundary and Subsequent Closure of the Iapetus Ocean
C) Collision of Island Arc and other Accreted (exotic) Terranes with
North America in the TACONIC OROGENY
CAMBRIAN
PALEOGEOGRAPHY:
SHALLOW
EPICONTINENTAL
SEAS COVERED THE
CENTRAL US
Earliest Paleozoic time
of lowest sea level due to
Proterozoic glaciations
By middle Cambrian sea
had flooded the continent
LITHOLOGIC FACIES OF THE CAMBRIAN
The transgression of the
Cambrian is visible in
the rocks of the Grand
Canyon
NEOPROTEROZOIC
TO CENOZOIC
TRANSGRESSIONS
AND REGRESSIONS
OBSERVED ON THE
CRATON
Variable sea level represented
sequences of sediments bounded
by unconformities on all of the
cratons - e.g. Sauk, Tippecanoe
ORDOVICIANPALEOGEOGRAPHY
Tippecanoe Transgression
St. Peter’s Sandstone
The Queenston Clastic Wedge
Redbeds coarser towards
the source area, Taconic
Highlands (4000m)
Early Paleozoic Climates
• Climates overall warmer than today
• Continents 600 N & S of equator
• Arid to sub arid environments 450 N & S
of equator
• Redbeds (alluvial) 300 N & S of equator
• Tropical reefs 300 N & S of equator
– Cambrian Archeocyathids; Ordovician
Bryozoans
• Glaciation during the late Ordovician in
Africa
PALEOZOIC LIFE
• Cambrian Explosion>Break up of Rodinia
– radiation of all phyla>Continental Shelves
•
•
•
•
Cambrian Reef Systems
Cambrian extinctions (2nd largest)
Ordovician radiation
Global Faunas (Cambrian vs. Paleozoic
Faunas)
• Ordovician Reef Systems
• End-Ordovician extinction events
THE TOMMOTIAN FAUNA
Small Shelly Fossils
1-2 mm
Calcium phosphate
Calcium cqarbonate
Most phyla represented
1 to 2 MY duration
Trilobite Radiation
•
•
•
•
Comprise 95% of all Cambrian Fossils
Most successful arthropod
Chitinous shell with an underlayer of calcite
5 major extinctions during the Cambrian and
associated radiations
• Each Cambrian Biomere involved the
extinction of 40 to 95% of existing trilobite
genera
THE BURGESS SHALE
Fine grained turbidite deposit at the base of a reef
THE BURGESS FAUNA
Anomalocaris
Opabinia
Hallucigenia
Archaeocyathids &
Stromatoporoid Reefs
•Archeocyathid Reefs begin during
the Tommotian Stage in Siberia
•Spread rapidly through world
•Extinct by Early Cambrian
•Stromotoporoid Reefs begin during
the Middle Cambrian
•They remain a dominant reef
builder until the Devonian
Ordovician Life
• Terminal Cambrian trilobite extinction
led the way for rapid Ordovician
radiations in other groups
• Radiation of molluscs particularly
gastropods decreased importance of
stromatolites
• Tabulate and Rugose coral reefs
• Graptolites as index fossils
• Emergence of land plants
• First Vertebrates
Ordovician Extinctions
• Blackriver-Trenton
– Mid Ordovician, catastrophic regional
extinction
– All echinoderms and cephalopods; 90%
trilobites, 83% pelecypods
• Terminal Ordovician Extinction
– Major glaciation in Gondwana (sea level drop]
– 3rd largest in recorded geologic history; 80%
of all genera
THE MIDDLE PALEOZOIC
THE SILURIAN 438-408 MY
SILURES>> WELSH TRIBE
Roderick Murchison 1835
THE DEVONIAN 408-360 MY
(Old Red Sandstone)
DEVON>> County in SW England
Roderick Murchison
Adam Sedgwick 1839
INTRODUCTION
• Silurian
– 30 MY Duration
• Devonian
– 48 MY Duration
• Final Collision and Suturing of Baltica and
Laurentia
• Caledonian and Arcadian Orogenies
• High Stands of Sea Level
• Epicontinental seas; marine deposits and
thick sequences of evaporites
• Reefs became important
Paleogeography
PALEOGEOGRAPHY
• Closing of Iapetus Ocean
– Baltica-Laurentia; Mongolia-Siberia
• Closing of Rheic Ocean as Gondwana migrated to
west (Laurentia/Baltica-Gondwana)
• Laurentia continued to be a tropical craton
• Shallow seas covered the continents during much of
Silurian
• Devonian orogenies in Northern Hemisphere
– Caledonian (Scandinavia/Greenland) & Acadian (New
England) & Antler (CA-NV)
Cratons and Mobile Belts of North America and Europe
TECTONIC EVENTS
• Caledonian & Acadian Orogenies
– Extension of Late Ordovician Taconic Orogeny
• Mid Devonian Iapetus Ocean closed
• Baltica collided with Laurentia
• Avalonia (Island Arc) sutured to both Baltica
and Laurentia
• Norway collided Greenland forming the
highlands responsible for the Old Red
Sandstone
Orogenic
Development
Of the Eastern
US
Acadian Orogeny produced
a thick clastic wedge (the
Catskill Wedge) of red beds
[conglomerates and sandstones]
East-West Cross Section across the Devonian Catskill Wedge
During the Devonian the rate of
sedimentation increased from
7m/MY to 17m/MY to 70m/MY
Chattanooga Shale- Anoxic black shale, marker bed
Lithofacies &
Thickness Map
of the Upper
Devonian
Sequence of
the Eastern US
The Appalachians
• Valley and Ridge
– folded & faulted sedimentary rks
• Blue Ridge Province
– metamorphosed Precambrian and Paleozoic Rks
• Inner Piedmont
– high grade metamorphic rks intruded by granites
• Charlotte & Carolina Slate Belt
– metamorphosed & folded late Proterozoic &
Cambrian sediments and volcanics
Physiographic Provinces of the Appalachian Region
Highland
Areas
Associated
with the
Antler
Orogeny of
CaliforniaNevada
Domes and Basins
Vertical Uplift and Subsidence
Erosional and Depositional Features
Depositional Basins of the North
American Craton
Model Illustrating the Deposition of Evaporites
Michigan Basin
Cyclic: Dolomite, Anhydrite, Halite
1500 m of carbonates, rock salt and gypsum
in 5 major cycles
NEOPROTEROZOIC TO CENOZOIC TRANSGRESSIONS AND
REGRESSIONS OBSERVED ON THE CRATON
Variable sea level
represented sequences of
sediments bounded by
unconformities on all of
the cratons -
Highest Stand of sea Level
Oriskany
Sandstone
Kaskaskia
Transgression
The Reef System
• Tabulate corals and Stromotoporoid
sponges
• Fauna was vertically zoned (tiered by
depth)
• Clear ecological succession in reef
building from pioneer community
(clumps of twig-like colonies) to platy
and domed shaped colonies to binding
stage by sponges
• Michigan, Canning Basin (Australia),
British Columbia
Mineral Deposits
• Sedimentary copper, lead and zinc sulfides and
Iron ores
• Occur in shales and carbonates
• Disseminated or interbedded
• Tri-state mining district (MO)
• Howard’s Pass, Yukon, Canada
• Wales
• New York to Alabama
Clinton
Iron Ore
Silurian Clinton Group near Birmingham, AL
The ore is an oolite of hematite (iron oxide)
Other Economic Deposits
• Silurian Salt, Michigan and upstate New
York
• Silurian Petroleum Deposits-OH, OK,TX
• Devonian Petroleum Deposits
– Williston Basin- MT and Alberta
– First oil well in US 1859 (PA)
• Silica for glass- Devonian Oriskany
Sandstone, 95-99.8% pure
Mid-Paleozoic Climates
• Gondwana centered over the South Pole
– climates ranged from cold to warm
– glacial striations present in South America yet
Red beds and carbonates and evaporites were
also present in N. Africa, India and Australia
• Other continents were equatorial
– Laurentia, Baltica and Siberia were warm
MID PALEOZOIC LIFE
• The Origin of the Ammonoids
– Cephalopods, Devonian
– Evolved from straight chambered nautiloids
• Eurypterids and the Origin of Arachnids
– Chelicerata (horseshoe crabs and sea
scorpions)
– Ferocious predators of the Paleozoic seas
Life of the
Silurian
Eurypterids
Devonian forms reached 2 m
Huge eyes and pincers
Radiation of Fishes
• During Cambrian and Ordovician only 1 order
of fish, jawless, Ostracoderms (Marine)
• Early Silurian 3 more orders of jawless fish
and the first jawed fish, acanthodian,
appeared and inhabited both marine and
fresh water
• By Middle Devonian all classes of jawed fish
had appeared
• All restricted to 40o of the equator
• Extinction at end of Devonian, terminated the
ostracoderms and the armored placoderms
Evolution of
the 5 Major
Groups of
Fishes
Ostracoderms
A: Thelodus
B: Pteraspis
C: Jamoytius
D: Hemicyclaspis
Evolution of Jaws in Fish
Placoderms
Skull 1 m high
fish 10m long
Dunkleosteus
The Origin of Tetrapods
Amphibian
Crossopterygians
Ichthyostega
Late Devonian (Old Red Sandstone)
One of the Oldest Known Amphibians
The Radiation of Land Plants
• Earliest Fungi appear in the Early
Silurian
• First Land Plants are Late Ordovician
• First Vascular Plants are Late Silurian
• With the appearance of forests in Late
Devonian oxygen levels increased and
reached a peak in the Late Paleozoic
• Land erosion rates significantly
decreased
The Development of Tiering
• Vertical Separation Between Organisms
– Removes competition between organisms of
similar feeding habits
• Different stalk heights in crinoids
• Low herbaceous plants grading into true
forest with tall trees
Terrestrial Communities
• By Early Devonian land communities were
diverse
• Rhynie Chert (Aberdeen, Scotland)
• Silicified peat bog
• Preserved plants as well as spiders, mites
and insects
Mass Extinction
• Major marine extinction of the Late Devonian
– Frasnian-Famennian epochs
• 33% marine families became extinct
• Nearshore marine and reef benthic species
– corals, stromotoporoids, all but 1 order of
trilobites, many brachiopods and ammonoids
• No corresponding terrestrial extinction
Frasnian-Famennian Extinction
• Occurred during a regression
• Associated with low oxygenated water and
high metal concentrations
• Sharp drop in temperature (O2-Isotope
studies)
• Presence of glass spherules
• All indicate a probable asteroid impact which
caused deep anoxic and high metallic content
water to poison shoal communities