W3+4 - Early Paleozoic

Question 1

What was the latest ice age?

Answer 1

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

Question 2

When was the last glacial maximum?

Answer 2

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

Question 3

When was life originally believed to have became complex?

Answer 3

Between the Ediacaran Period of the Precambrian and the Cambrian Period

Question 4

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

Answer 4

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

Question 5

When was the Ediacaran Period?

Answer 5

635-541mya

Question 6

What are the oldest possible eukaryotes?

Answer 6

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

Question 7

What are Metazoan fossils?

Answer 7

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

Question 8

What was the first Metazoan fossil discovered?

Answer 8

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

Question 9

Where did the earliest Canadian organism evolve?

Answer 9

Found at Mistaken Point, Newfoundland

Question 10

What was the Ediacaran Period named after?

Answer 10

Ediacaran Hills, Australia

Question 11

What is a Petalonomae fossil?

Answer 11

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

Question 12

What are Ernietta fossils?

Answer 12

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

Question 13

What are Bilaterian fossils?

Answer 13

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

Question 14

What are some examples of Bilaterian fossils?

Answer 14

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)

Question 15

What are Trilobozoan fossils?

Answer 15

Motile
Tri-radial symmetry
Hard to classify

Question 16

What are Cloudina fossils?

Answer 16

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

Question 17

When are most Ediacaran fossils found?

Answer 17

Between 575-541mya

Question 18

When was the Cambrian period?

Answer 18

541-485.4mya

Question 19

When was the Cambrian explosion of life?

Answer 19

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

Question 20

What is the Burgess Shale?

Answer 20

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

Question 21

What is unique about the Burgess Shale?

Answer 21

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

Question 22

How did the Burgess Shale form?

Answer 22

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

Question 23

What is the Opabinia regalis fossil?

Answer 23

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

Question 24

What is the Anomalocaris canadensis fossil?

Answer 24

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)

Question 25

What are Radiodont fossils?

Answer 25

Highly successful and diverse group known to have lived through the Devonian period

Question 26

What are Lobopod fossils?

Answer 26

Lobe-feet animals
Segmented
Have mouths
Spines for protection
Now thought to be ancient Onychophorans

Question 27

What are Panarthropod fossils?

Answer 27

Includes the lobopod and radiodont groups
Thought to be stem ancestors of the Arthropods

Question 28

What are some examples of Cambrian fauna?

Answer 28

Marella = an extinct arthropod, similar to a trilobite
Yohoia = two front appendages, arthropod
Metaspringgina = early chordate, initially thought to be related to Springgina

Question 29

What was the geology of Cambrian North America like?

Answer 29

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

Question 30

What happened to the Iapetus Ocean?

Answer 30

Precursor to Atlantic Ocean
During the early to mid-Ordovician (450mya), Laurentia drifted towards Baltica and Gondwana, closing the ocean

Question 31

How were the Taconic Mountains formed

Answer 31

Through the repeated collision of Laurentia with Baltica (SA)

Question 32

What is a clastic wedge?

Answer 32

Thick accumulation of sediment or sedimentary rocks in lens shape
Thin near the mountain front, thickens landward, then becomes thinner further inland

Question 33

What is the Queenston Clastic Wedge?

Answer 33

~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

Question 34

How is the Queenston Clastic Wedge represented in the Niagara Escarpment?

Answer 34

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)

Question 35

When did uplift of Taconic Mountains stop?

Answer 35

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)

Question 36

How are the Silurian Tropical Seas represented in the Niagara Escarpment

Answer 36

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)

Question 37

How did Silurian Reefs die out?

Answer 37

Near end of Silurian
Climate became warmer and more arid
Sea regressed exposing reefs - reefs died
Extensive tidal flats (sabkhas) formed

Question 38

How are evaporites formed?

Answer 38

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

Question 39

What are common evaporite minerals?

Answer 39

Halite, anhydrite, gypsum, sylvite, kieserite, bischofite

Question 40

Where is the largest salt mine in the world?

Answer 40

Goderich - where the Silurian sedimentary rocks are most exposed

Question 41

How thick is the Silurian basin located under Hamilton?

Answer 41

800m
Thicken westward and eastward into the Appalachian and Michigan basins

Question 42

What is the dip of the Paleozoic strata?

Answer 42

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)

Question 43

What was life like in the Paleozoic?

Answer 43

Life still mainly remains in the seas
Includes brachiopods, corals, eurypterids, trilobites, and cephalopods

Question 44

What was the Ordovician diversification?

Answer 44

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

Question 45

What are crinoid fossils?

Answer 45

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)

Question 46

What are cephalopod fossils?

Answer 46

Squid-like animals with coiled or straight shell with internal chambers
Carnivorous and pelagic (live and swim in open water column)

Question 47

What are tabulate coral fossils?

Answer 47

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

Question 48

What are eurypterid fossils?

Answer 48

Also known as sea scorpions
Aquatic invertebrates (brackish estuaries)
Have nasty pincers
Can grow up to 3m long
Present from the Ordovician to Permian

Question 49

What are brachiopod fossils?

Answer 49

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)

Question 50

What is a mass extinction event?

Answer 50

Episodes of globally-significant extinctions
Reduction of species diversity
Two definitions: >20% marine genera become extinct or 75% of all species become extinct

Question 51

How many mass extinction events have there been?

Answer 51

5, throughout the Phanerozoic
Includes the Late Ordovician, Late Devonian, Late Permian, Late Triassic, and Late Cretaceous (mark the end of a period)

Question 52

What was the Late Ordovician Extinction?

Answer 52

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