The Paleozoic
Life and Times
Major Events in the Paleozoic
• Tectonics
– Formation of Gondwana
– Formation of Eurasia
– Formation of Pangea
• Extinctions
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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
60 N
P
South
China
P
O
P
le
ne
lli
d
Laurentia
P
Iapetus
30 S
P
AP
Siberia
Aegir
P Sea
Baltica
P
Armorica
m
R
ea
l
d
P
P
A A
Avalonia
P P
P
Gondwana
Pa
leo
Oc P a c i
ea fic
n
R
ea
lm
A
A
ic
hi
i
Equator
P
P
R
ed
l
Paleo-Asian
Ocean
AP
P
A=Archaeocyathids of Tommotian/Atdabanian age
Subduction Zone
P=Phosphorite Occurrences (Parrish et al., 1986)
Humid Tropical Zone
30 N
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
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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
Nautoloids
Crinoids
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 NELaurentia.
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 preDevonian (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
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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
Jawless fish
Eurypterids
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
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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)
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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