Week 15

Question 1

Cambrian overview

Answer 1

Explosion

Earliest animal with notochord = Pikaia Gracilens

Warm/humid

High sea level

Current circulating

Few continents at poles

Question 2

Ordovician overview

Answer 2

High sea level

Gondwana drifting S

Lots of carbonate deposition

Low continental erosion (flat)

1st terrestrial land plants = liverworts

Mycorrhizal fungi

Question 3

Mycorrhizal fungi

Answer 3

Enhances P from soil to roots

• increase SA
• release phosphatase = enhances P uptake
• releases organic acids = enhances mineral weathering

Question 4

Ordrovician glaciation

Answer 4

Last ~1Ma

Atmospheric CO2 7000-4000ppm

= horizontal sea level drop (extreme)
= 2nd largest extinction (-60% marine species)

Caused by Appalachian orogeny and silica weathering/CO2 effect

Question 5

Silurian overview

Answer 5

Gondwana high S lats

Panthalassa ocean covered most N hemisphere

Baltica/Avalonia = Caledonian Orogeny

~Glaciation
Increasing SL
= climate stabilisation

1st jawed fish and vascular plants e.g. cooksonia
- cells that enhance fluid conduction

Question 6

Devonian overview

Answer 6

Laurentia/Baltica = supercontinent

Gondwana still high S lats

High sea level = sedimentary rock deposition and lots of submerged land

Gilboa forest

Terrestrial equivalent to Cambrian explosion

End = mass extinction

• :( benthic marine shallow tropical
• :) deep/high latitudes

Question 7

Devonian forests

Answer 7

Deep roots = increase pedogenesis (break rocks)

Webbed leaves = cool shade

New “forest” biome

More organic matter in streams = black shale

Decreased surface albedo 10-15%

Amazing perseveration: silicified CALDOXYLOPSIDA (hollow middle and very complex????)

Question 8

Cause of Devonian mass extinction

Answer 8

DEVONIAN PLANT HYPOTHESIS
More continent erosion = ocean eutrophication
More silicate weathering = glaciation
(Like Ordovician mass extinction)

VOLCANIC
Mercury spike in sediment

Question 9

Carboniferous summary

Answer 9

High SL

Warm early, ice on Gondwana/increases through

Coal swamps low lats

Pangaea

Permo-Carboniferous massive ice age

Carbon stored in coal
- trees in tropical = x rings b/c no seasonality

Land plants: LEPIDODENDRON/SIGILLARIA

1st conifers

Amphibians/spiders/insects

High O2 = gigantism

Question 10

Evidence for carbon stored in coal during carboniferous

Answer 10

COAL SEAMS

CYCLOTHEMS
- periodically inundated

O ISOTOPES
- photosynthesis

C ISOTOPES
- peak in 13C b/c plants love 12C and buried

Question 11

Oxygen limit

Answer 11

30%

Question 12

Permian overview

Answer 12

Ferns —> more advanced conifers/ginkgo trees

Desert established

Insects and reptiles radiated
COLEOPTERA (beetles)
DIPTERA (flies)

End = largest mass extinction (-96% animal species)

Question 13

Causes for Permian mass extinction

Answer 13

GLACIATION

PANGAEA FORMATION

SIBERIAN TRAPS

METEOR

FOSSIL FUEL BURNING

Question 14

1st order tectonic features during Permian examples

Answer 14

Variscan orogeny

Ural Mountains

Ancestral Rocky Mountains

Question 15

Evidence for tectonic features during Permian/how we can reconstruct orogeny timings

Answer 15

87Sr/86Sr show silicate weathering rates

Depend on:

Non radiogenic deep sea hydrothermal

Continental weathering radiogenic riverine sources

Continental crust 87Rb—>87Sr

Question 16

Stomata

Answer 16

SI = stomatal index

More = low CO2

BUT

• response is species dependent
• only when leaves preserved/existed

Question 17

How did Wegner come up with the Permo-Carboniferous ice age? And some facts

Answer 17

Odd striations

Max extent lasted ~20Ma
~150-250 m SL change
Tropics ~warm