The Paleozoic

Life and Times

Major Events in the Paleozoic

• Tectonics –Formation of Gondwana

–Formation of Eurasia

–Formation of Pangea

• Extinctions – Cambrian

– Ordovician

– Devonian

– Permian

The Paleozoic Runs from 542 Ma to 251 Ma

Periods:

Cambrian 542-488 Ma

Ordovician: 488-444 Ma

Silurian: 444-416 Ma

Devonian: 416-359 Ma

Carboniferous: 359-299 Ma

Mississippian: 359-318 Ma

Pennsylvanian: 318-299 Ma

Permian: 299-251 Ma

Major Events in the Paleozoic

• Sea Level Changes (highs and lows)

– Cambrian high

– Ordovician and Carboniferous lows

• Climatic Changes (glaciations)

– Ordovician

– Permo-Carboniferous (severe)

Cambrian 542-488 Ma

The Cambrian Period

• Cambrian System. [1835] Named by Adam Sedgwick for Transitional rocks in Wales that are found below Murchison's Silu-rian System.

• Sedgwick did not recognize any fossils. Sedgwick based his system on lithology, not fossils (it wasn't until the 1850's that fossils were discovered in his type Cambrian section).

• Since, in the mid-1800's, fossils were viewed as essential for the naming and recognition of systems, the Cambrian wasn't accepted by many people.

• It wasn't until 1879 with Lapworth's establishment of the Ordovician, that the Cambrian was reinstated (and was based on fossils).

Major Events in the Cambrian

Period (542-488 Ma)

1. The rise of animals- The Cambrian Expansion (Tommottian time).

2. Early rich lagerstatte such as Burgess Shale (Canada) and Chengjiang (China).

3. Nearly every metazoan phyla began in the Cambrian

4. Development of hard parts (phosphatic, calcitic and chitonous skeletons).

5. Formation of the Gondwana supercontinent

6. Climate was moderate to warm due to continental location

Tectonic Setting of the Cambrian

Equator

30 S

30 N

60 N

Laurentia

Gondwana

Armorica

Avalonia

Siberia

BalticaIapetus

AegirSea

A

A=Archaeocyathids of Tommotian/Atdabanian age

Subduction Zone

A

A

A A

Red

lichi

id R

ealm

Ole

nelli

d Rea

lm

SouthChina

A

Hu

mid

Tro

pic

al Z

one

Pal

eo P

acif

icO

cean

Paleo-AsianOcean

P

PP

P

P

P=Phosphorite Occurrences (Parrish et al., 1986)

P

P PP

P

P

P

P

P

P

P

P

Tectonic Setting of the Cambrian

• Gondwana (Africa, South America,

Madagascar, India, Antarctica, Australia

and Seychelles) forms at ~530 Ma.

• Laurentia (North America) located near the

from mid-south lats to equator

• Iapetus Ocean opened and has started to

close

• Siberia also located near the equator

Burgess Shale Fauna

The Burgess Shale

• Burgess shale fauna are a mix of soft and

hard bodied animals. There is evidence

for predation. It is likely that predatory

behavior was responsible for the

development of hard exoskeletons.

The Cambrian Climate and Sea

Level

• Sea level was generally high in the

Cambrian (trangressions) and this resulted

in shallow, warm-water seas perfect for

life.

Cambrian Sea Level Map

Diagnostic Fauna of the Cambrian

• Trilobita

• Brachiopoda

• Archeocyathids

• Echinoderms

Cambrian Fauna

Cambrian Extinction

• At least four major extinctions occurred during the Cambrian. The first extinction occurred at the Early Cambrian epoch boundary.

• During this event, the oldest group of trilobites, the olnellids, perished as well as the primary reef-building organisms, the archaeocyathids.

• The remaining three extinctions were irregularly distributed around the Late Cambrian epoch boundary, and as a whole, severly affected trilobites, brachiopods, and conodonts.

The Ordovician (488-444 Ma)

• The Ordovician Period is the second period of the Paleozoic Era.

• This important period saw the origin and rapid evolution of many new types of invertebrate animals which replaced their Cambrian predecessors.

• Primitive plants move onto land, until then totally barren.

• The supercontinent of Gondwana drifted over the south pole, initiating a great Ice Age that gripped the earth at this time. The end of the period is marked by an extinction event.

Ordovician Origins

• Ordovician System. [1879] Charles

Lapworth established the Ordovician from

studies in Wales and elsewhere based on

distinctive graptolite fossils.

• By this time trilobites were known from

rocks below classical Silurian (in

Sedgwick's Cambrian)

Major Ordovician Events

• Major Transgression in the Middle

Ordovician.

• Major Regression in the Late Ordovician

related to Gondwana glaciations.

• Major radiation following the Cambrian

extinctions.

• Rise of the cephalopods (intelligence

increase in the Ordovician)!

Evolutionary Events

• Molluscs-

– Cephalopoda- Nautiloids, ammonites

– Gastropoda- snails

– Bivalves- clams

• Crinoids- Rich variety of crinoids also

known as sea-lilies

• Bryozoa- ‘moss animals’ colonials

• Corals- Rugosa and Tabulata

Crinoids

Nautoloids

Bryozoa

Rugose Corals

Tabulate Corals

Tectonic Events

• The beginning of the Appalachian

Mountain chain and ultimately Pangea

• Taconic Orogeny -collision of small blocks

of island arc and microcontinents with NE-

Laurentia.

Ordovician Extinction

• The Ordovician extinction occurred at the end of the Ordovician period, about 440-450 million years ago.

• This extinction, cited as the second most devastating extinction to marine communities in earth history, caused the disappearance of one third of all brachiopod and bryozoan families, as well as numerous groups of conodonts, trilobites, and graptolites.

• Much of the reef-building fauna was also decimated. In total, more than one hundred families of marine invertebrates perished in this extinction

Cause of Extinction

• The Ordovician mass extinction has been

theorized by paleontologists to be the

result of a single event; the glaciation of

the continent Gondwana at the end of the

period.

The Silurian (444-416 Ma)

• Silurian System. [1835] Established by Roderick Murchison for rocks with distinctive fossils that was originally classified as Transitional (a Wernerian term) in Wales.

• Silurian was the generally accepted pre-Devonian (Old Red Sandstone) system for all the Lower Paleozoic.

• Silures- Ancient Celtic tribe

The Silurian (444-416 Ma)

• Following the Gondwana glaciations, the

earth entered a greenhouse phase with

equable climates from pole to equator

• Recovery from the extinction was swift and

efficient leading to a rich biodiversity

• Major evolutionary change was a rich

terrestrial ecosystem.

• Major reef and evaporite formation

Evolutionary Events

• The most important evolutionary development of this period, was that of the first true terrestrial ecosystem

• The first fossil records of vascular plants, that is, land plants with tissue that carries food, appeared in the Silurian period. They were simple plants that had not developed separate stems and leaves.

• Brachiopods are the most common hard-shelled organisms, making up 80% of the total species.

• Tropical reefs are common in the shallow seas of this period, formed by tabulate and rugose corals, stromatoporoid organisms, bryozoa and calcareous algae. Trilobites, cephalopods, gastropods, and echinoderms.

• Planktonic graptolites remain common and diverse. The single-spined Monograptus is the predominant genus

• Jawless fish invade brackish and fresh water, as do eurypterids, xiphosurids, scorpions, which may have been semi-aquatic.

• At the end of the period Jawed fish appeared for the first time, but they remain insignificant.

Typical Silurian Fossils

Eurypterids

Jawless fish

Gastropods

Tectonic Events

• Final Closure of Iapetus Ocean during

Middle Silurian time

• Acadian Orogeny – Collision between

Baltica (northern Europe) with North

America.

• Narrowing of the Tethyan Ocean (between

Gondwana and Laurentia)

Acadian Orogeny

Silurian Extinctions

• No major Silurian extinctions although

trilobites continued to decline in

abundance during this interval.

The Devonian (416-359 Ma)

• The name Devonian was introduced in

1829 by Sir R. Murchison and A. Sedgwick

to describe the older rocks of Cornwall and

Devon.

• Nicknamed “The Old Red Continent”

because of the abundance of red

sandstones.

• Also called “The age of Fishes”

Old Red Sandstone

Major Devonian Events

• Acadian Orogeny

• The rise of Fishes

• The rise of tetrapods (terrestrial animals)

• Trees and forests appear on land

• Devonian climate was equable with many

continents situated on the equator, but

there were strong zonal climates as well.

• Frasnian-Fammenian Extinction

Evolution

• The rise of Fishes

• The start of tetrapods and the invasion of

land animals.

• The beginning of forests on land

• Devonian life is a hallmark step in

evolution as it marks the true ‘explosion’ of

terrestrial life.

From Fish to Land

Tetrapod

trackway found in

Kentucky.

The Fishes

Dunkleosteus

Great Moments

The Fish Related to Tetrapods (lobe-finned)

Eusthenoptyron- Lobe finned fish

Panderichthys

The Intermediates!

• This fossil was just discovered in

Greenland sometime last year

• It shows a transition from a true fish to a

true tetrapod (land dweller).

• It is called tiktaalik rosea

Tiktaalik Rosea

Acanthostega

Icthyostega

Plant Life in the Devonian

Cooksonia

Devonian Tectonics

• End of the Acadian Orogeny (formation of

Euramerica).

Euramerica

Devonian Extinctions

• Frasnian-Fammenian (~375 Ma)

• The Frasnian/Famennian Extinction Event affected both marine and terrestrial ecosystems, as demonstrated by the diversity record of marine invertebrates, land-plant

spores, and macrofloras. • A variety of causes have been proposed to explain the

Frasnian/Famennian event including climate change (both global warming and cooling) and increased influx of terrigenous sediments to continental shelves caused by the appearance and spread of deeply rooted forest ecosystems and gamma-ray bursts due to nearby supernovae explosions

Carboniferous Period (359-299 Ma) (Mississippian and Pennsylvanian)

• Mississippian (359-323 Ma) • Pennsylvanian (323-299 Ma) • Rise of complex forest ecosystems • Renowned for coal deposits • Formation of the Pangean Supercontinent • The name Coal Measures was proposed by Farey in 1807

and 1811. • The term Carboniferous was proposed by the English

geologist William Conybeare and William Phillips in a paper published in 1822.

• Alexander Winchell proposed the name Mississippian in 1869 for strata along the Mississippi River

• In 1891 Henry S. Williams suggested Pennsylvanian for the Upper Carboniferous