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W3+4 - Early Paleozoic Flashcards

(52 cards)

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1
Q

What was the latest ice age?

A

Cenozoic
Current era (66mya to present)
Began in Cretaceous-Paleogene Extinction event (Cretaceous-Tertiary extinction)
Quaternary period (last 2.58my) is particularly marked by ice ages

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2
Q

When was the last glacial maximum?

A

18 000ya
About 30% of world’s landmasses were covered in ice (vs 10% today)
Average temperature was 6C colder
More ice sheets present, including Laurentide
Antarctica has remained relatively the same

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3
Q

When was life originally believed to have became complex?

A

Between the Ediacaran Period of the Precambrian and the Cambrian Period

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4
Q

What events occurred at the end of the Ediacaran Period, before the Cambrian Era?

A

Break up of Rodinia caused the formation of shallow reef systems and the Iapetus Ocean (precursor to Atlantic Ocean), allowing for the increase of biodiversity
Overall rise of sea-level and warming through to the Ordovician (evidenced by change from sandstones upwards into carbonates)
Ediacaran fauna die out (possibly due to anoxic event)
- some metazoans survived into Cenozoic

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5
Q

When was the Ediacaran Period?

A

635-541mya

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6
Q

What are the oldest possible eukaryotes?

A

Metazoans are suggested to have first appeared 800-700mya before snowball earth (no fossil evidence)
Oldest multi-celled embryos are found in Doushantuo Formation in China, dated to ~600mya

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7
Q

What are Metazoan fossils?

A

Early synonym for the kingdom Animalia
Most fossils aren’t able to be connected to extant species

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8
Q

What was the first Metazoan fossil discovered?

A

Charnia
Discovered by English schoolchildren in the Charnwood Forest, England
Originally thought to be from the Cambrian (wasn’t believed fossils could exist in rocks any older) but later realized to be Late Proterozoic
Originally thought to be related to modern sea pens (cnidarian) - very different
Not a plant as it would’ve been too deep for photosynthesis to occur

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9
Q

Where did the earliest Canadian organism evolve?

A

Found at Mistaken Point, Newfoundland

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10
Q

What was the Ediacaran Period named after?

A

Ediacaran Hills, Australia

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11
Q

What is a Petalonomae fossil?

A

Petal animal
Has no feeding structures, organs, stinging cells, or body cavity
Fractal body plan increased surface area
Probably an osmotroph (fed by osmosis)
No modern counterparts - represent a long extinct clade
Ex: Charnia

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12
Q

What are Ernietta fossils?

A

Found in shallow water sandstones (Namibia)
Live partially buried in the sediment
Thought to be osmotrophic

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13
Q

What are Bilaterian fossils?

A

Motile
Belong to extinct clade - no known modern examples
Feeding mechanism unknown - maybe in situ osmosis, maybe aided by cilia

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14
Q

What are some examples of Bilaterian fossils?

A

Springgina = distinct head, tail, and segments, no mouth parts
Kimberella = grazing traces, may have been a stem mollusc
Parvancorina = vaguely trilobite like (but not related)

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15
Q

What are Trilobozoan fossils?

A

Motile
Tri-radial symmetry
Hard to classify

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16
Q

What are Cloudina fossils?

A

Calcium carbonate skeletons
Probably more complex than stromatolites
Named after Canadian paleontologist, Cloud
Not clear what phyla these belonged to

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17
Q

When are most Ediacaran fossils found?

A

Between 575-541mya

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18
Q

When was the Cambrian period?

A

541-485.4mya

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19
Q

When was the Cambrian explosion of life?

A

Started ~538.8mya
Possibly caused by increase in oxygen or increase in carbonate concentration (allow for skeletons to form to protect organisms)
All principal groups developed between 530-520mya
Shelled forms developed
Trace fossils record complex behaviour

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20
Q

What is the Burgess Shale?

A

Middle Cambrian shale in Alberta
Discovered by Charles Walcott of the Smithsonian Institute who collected over 65000 fossils by 1924 - quarry named after him
Exposed near Mt. Wapta, BC

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21
Q

What is unique about the Burgess Shale?

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A

Contains very strange organisms - some of which have little similarity to present-day organisms
Weird forms represent early experimentation of evolutionary life in uninhabitated niches
Very rich fossil record

22
Q

How did the Burgess Shale form?

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A

508mya
Collapse of carbonate reef top deposited shallow water fauna in muds at the deep marine base of the escarpment
Conditions (shales and muds) allowed preservations of soft parts
Unknown if fossilized organisms lived at escarpment base or reef top

23
Q

What is the Opabinia regalis fossil?

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A

5 eyes
Has a proboscis (long and mobile nose)
No legs
Segmented
Back and side fins
Uncertain how it is related to modern organisms

24
Q

What is the Anomalocaris canadensis fossil?

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A

Parts of it were originally believed to be a shrimp tail, jellyfish, or sponge
Largest predator in the Cambrian
Two eyes on stalks
Side and back fins
No legs
Now assigned to Radiodonta (spoke tooth)

25
What are Radiodont fossils?
Highly successful and diverse group known to have lived through the Devonian period
26
What are Lobopod fossils?
Lobe-feet animals Segmented Have mouths Spines for protection Now thought to be ancient Onychophorans
27
What are Panarthropod fossils?
Includes the lobopod and radiodont groups Thought to be stem ancestors of the Arthropods
28
What are some examples of Cambrian fauna?
Marella = an extinct arthropod, similar to a trilobite Yohoia = two front appendages, arthropod Metaspringgina = early chordate, initially thought to be related to Springgina
29
What was the geology of Cambrian North America like?
Period of tectonic stability (no collisions between continents, stayed still) Passive divergent margins along east and west coast - allowed for diverse life forms Carbonates and sands deposited in shallow inland seas (only found in Ottawa area) NA was located near the equator Surrounded by shallow seas 'Epeiric' (on the craton) seas - water infilled the continent
30
What happened to the Iapetus Ocean?
Precursor to Atlantic Ocean During the early to mid-Ordovician (450mya), Laurentia drifted towards Baltica and Gondwana, closing the ocean
31
How were the Taconic Mountains formed
Through the repeated collision of Laurentia with Baltica (SA)
32
What is a clastic wedge?
Thick accumulation of sediment or sedimentary rocks in lens shape Thin near the mountain front, thickens landward, then becomes thinner further inland
33
What is the Queenston Clastic Wedge?
~480km clastic wedge of sediment Clastic sediment eroded from Taconic mountains and was transported to sea by inland rivers, forming huge deltas which prograded westward
34
How is the Queenston Clastic Wedge represented in the Niagara Escarpment?
Queenston shale Whirlpool sandstone = clean (no other sediment types), cross-bedded sandstone, deposited in river system feeding large delta Grimsby shale and Thorold sandstone = interbedded sandstones and shales (indicate different energy levels), deposited in shallow sea, wave ripples and hummocky cross-beds in sandstones (indicate waves and storm events)
35
When did uplift of Taconic Mountains stop?
Mid-Silurian (430mya) Input of clastic sediments reduced Allowed for deposition of limestones and dolostones (chemically precipitated and bioclastic), some shale (little sediment input - sediment pulses)
36
How are the Silurian Tropical Seas represented in the Niagara Escarpment
Lockport and Irondequoit limestones and dolostones Rochester shale (from some sediment input) Differing bed thickness of Lockport members is caused by differences in interruptions (as beds are represented by uninterrupted deposition)
37
How did Silurian Reefs die out?
Near end of Silurian Climate became warmer and more arid Sea regressed exposing reefs - reefs died Extensive tidal flats (sabkhas) formed
38
How are evaporites formed?
In shallow, restricted basins surrounded by fringing reefs Sea water evaporates rapidly, precipitating salts Deposits formed in arid basins Evaporation of 1000m sea water yields about 0.75m gypsum and 1.37m salt
39
What are common evaporite minerals?
Halite, anhydrite, gypsum, sylvite, kieserite, bischofite
40
Where is the largest salt mine in the world?
Goderich - where the Silurian sedimentary rocks are most exposed
41
How thick is the Silurian basin located under Hamilton?
800m Thicken westward and eastward into the Appalachian and Michigan basins
42
What is the dip of the Paleozoic strata?
Dip gently (<1 percent) to SW due to the shape of the basin Strike NE to SW (with youngest rock to the SW - where sediment overlays the Canadian shield)
43
What was life like in the Paleozoic?
Life still mainly remains in the seas Includes brachiopods, corals, eurypterids, trilobites, and cephalopods
44
What was the Ordovician diversification?
485-443mya Families of marine organisms increased from 160 to 530 - particularly among trilobites, brachiopods, bivalve mollusks, and gastropods Caused by mountain building events and volcanisms (different altitudes) - cause diverse environments
45
What are crinoid fossils?
Also known as sea lilies Sessile animals attached to the sea floor Gather food particles from the water with arms Stems consist of plates that fall apart when the animal dies, leaving ossicles that are often seen as fossils Crinoidea class was much more diverse in Ordovician than in present (700 current living species)
46
What are cephalopod fossils?
Squid-like animals with coiled or straight shell with internal chambers Carnivorous and pelagic (live and swim in open water column)
47
What are tabulate coral fossils?
Important reef builders Build their structures in sheets (tables) Captured small animals with tentacles/cilia Extinct, but related to modern corals ~300 species have been described/identified
48
What are eurypterid fossils?
Also known as sea scorpions Aquatic invertebrates (brackish estuaries) Have nasty pincers Can grow up to 3m long Present from the Ordovician to Permian
49
What are brachiopod fossils?
Bivalve molluscs with asymmetrical shell Sessile (bottom dweller) Filter-feeder Outnumbered trilobites by Ordovician Very common in Silurian (500 genera) but rare in present day (100 genera)
50
What is a mass extinction event?
Episodes of globally-significant extinctions Reduction of species diversity Two definitions: >20% marine genera become extinct or 75% of all species become extinct
51
How many mass extinction events have there been?
5, throughout the Phanerozoic Includes the Late Ordovician, Late Devonian, Late Permian, Late Triassic, and Late Cretaceous (mark the end of a period)
52
What was the Late Ordovician Extinction?
Also called the Ordovician-Silurian Extinction (marked the end of Ordovician and start of Silurian) 57% of marine genera disappeared (21 families of trilobites, brachiopods, bivalves, corals) Killed 85% of marine species Probably occurred over several million years in two phases Caused by glaciation (Sahara) - lowered sea levels and diminished habitats, lowered temperatures, ice sheets blocked photosynthetic organisms on sea floor

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