THE EARLY PALEOZOIC

THE CAMBRIAN 544-505 MYCAMBRIA>>WALES ADAM SEDGWICK 1835

THE ORDOVICIAN 505-438 MYORDOVICE>>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 MYTYPE LOCALITY>>BURIN PENINSULA, NEWFOUNDLANDCAMBRIAN 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 RODINIAAVALONIAN OROGENYOPENING OF IAPETUSOPENING OF RHEICTACONIC OROGENY

CLOSING OF IAPETUSACADIAN 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 DepositsB) Middle to Late Ordovician Development of Trench Along the Eastern Boundary and Subsequent Closure of the Iapetus OceanC) 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 timeof lowest sea level due toProterozoic glaciationsBy middle Cambrian seahad flooded the continent

LITHOLOGIC FACIES OF THE CAMBRIAN

The transgression of theCambrian 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

ORDOVICIAN-PALEOGEOGRAPHY

Tippecanoe TransgressionSt. Peter’s Sandstone

The Queenston Clastic WedgeRedbeds coarser towardsthe source area, TaconicHighlands (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 FAUNASmall Shelly Fossils1-2 mmCalcium phosphateCalcium cqarbonateMost phyla represented1 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 SHALEFine 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 MYSILURES>> WELSH TRIBE

Roderick Murchison 1835THE 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

OrogenicDevelopmentOf the Eastern

US

Acadian Orogeny produced a thick clastic wedge (the Catskill Wedge) of red beds[conglomerates and sandstones]

During the Devonian the rate of sedimentation increased from 7m/MY to 17m/MY to 70m/MY

Chattanooga Shale- Anoxic black shale, marker bed

East-West Cross Section across the Devonian Catskill Wedge

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 California-

Nevada

Domes and BasinsVertical Uplift and SubsidenceErosional and Depositional Features

Depositional Basins of the North American Craton

1500 m of carbonates, rock salt and gypsumin 5 major cycles

Cyclic: Dolomite, Anhydrite, Halite

Model Illustrating the Deposition of EvaporitesMichigan Basin

Variable sea level represented sequences of sediments bounded by unconformities on all of the cratons -

Highest Stand of sea Level

NEOPROTEROZOIC TO CENOZOIC TRANSGRESSIONS AND REGRESSIONS OBSERVED ON THE CRATON

Oriskany SandstoneKaskaskia

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 mHuge 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: ThelodusB: PteraspisC: JamoytiusD: Hemicyclaspis

Evolution of Jaws in Fish

Placoderms

Dunkleosteus

Skull 1 m highfish 10m long

The Origin of Tetrapods

Crossopterygians

Amphibian

IchthyostegaLate 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