The Great Ordovician Biodiversification Event

Question 1

What is the GOBE?

Answer 1

Great Ordovician Biodiversification Event

Question 2

What developed from phylla?

Answer 2

Classes which are the taxonomic level below phylla

Question 3

What are the series of the Ordovician?

Answer 3

Lower
Middle
Upper

Question 4

What are the ages of the Ordovician?

Answer 4

Tremadocian
Floian
Dapingian
Darriwilian
Sandbian
Katian
Hirnantian

Question 5

What dispute was resolved by Charles Lapworths discovery of the Ordovician?

Answer 5

Between Murchinson wanting to extend the Silurian down in the rock record and Sedgewick wanting to extend the Cambrian up

Question 6

What do golden spikes represent on the chronostratigraphic chart?

Answer 6

where a rock sequence has been identified to represent type of sequence for that boundary

Question 7

What is an example of the “golden spike” for the base of the Ordovician system?

Answer 7

Green Point, Newfoundland
FAD (first appearance datum) - Iapetognathus fluctivagus

Question 8

What biostratigraphy can be used to identify the base of the Ordovician?

Answer 8

Taxon which look like conodonts - soft eel like (occur globally)

Question 9

What debate is ongoing concerning the Ordovician?

Answer 9

Whether its a continuation of the Cambrian or its own event

Question 10

What is the variation of substrate mobility between the Cambrian and the Ordovician?

Answer 10

Substrate mobility increased due to increased burrowing and movement into the water column

Question 11

What name was given to organisms which moved into the water column in the Ordovician?

Answer 11

Macro plankton

Question 12

What is also evidence of a shift to more life in the water column?

Answer 12

Suspension feeder (nutrients and food off the sediment floor)
Zooplankton - animals in water column

Question 13

What cased a revolution in the oceanic trophic levels in the Ordovician?

Answer 13

Acritarch’s

Question 14

What are acritarch’s?

Answer 14

Small flask shape organic fossils (suggested low level part of Ordovician food chain)

Question 15

What is class Graptolithina?

Answer 15

Mode of life Graptolids
Wholly planktonic
Wide variety of sediments

Question 16

What was a “kick” for biodiversification in the Ordovician?

Answer 16

Establishment of reef communities (modern day hotspots for diversification)

Question 17

What are the causes of GOBE?

Answer 17

Elevated sea levels
Global cooling
Raised atmospheric O2
Elevated oceanic nutrients
Asteroid shower

Question 18

How did elevated sea levels cause GOBE?

Answer 18

Cratonic flooding- increased area due to dispersal of continental areas (produced many shallow shelf environment, high energy and reef environment)

Question 19

How is it thought that global cooling caused the GOBE?

Answer 19

Decline of ocean temp into the middle Ordovician, corresponding with diversification pulses (temp decreased to modern day equatorial temp)

Question 20

What is the EPI?

Answer 20

Early Palaeozoic Ice house

Question 21

How is EPI linked to GOBE?

Answer 21

Ice caps can lead to diversification and help generation of ocean currents distributing nutrients and factor of weathering

Question 22

How is increased atmospheric O2 linked to GOBE?

Answer 22

Increased atmo O2 men more dissolved in ocean, O2 is fundamental part of respiration for many organisms

Question 23

What caused increased oceanic nutrient levels?

Answer 23

Growth of polar icecap drives deep water currents creating upwelling zones ventilating depth

Question 24

How are asteroids linked GOBE?

Answer 24

Intermediate disturbance hypothesis

Question 25

What is the intermediate disturbance hypothesis?

Answer 25

asteroid causes small change in surface conditions which forces adaptation and diversification of species

Question 26

What are found with Ordovician rocks in Sweden?

Answer 26

Lumps of asteroid

Question 27

What evidence of extra terrestrial rock is there in the Darriwilian?

Answer 27

Spikes in Chromite

Question 28

Where is there evidence of elevated flux of cosmic spherules? (Ordovician)

Answer 28

Durness group NW scotland

Question 29

What was mortality rate of the End Ordovician extinction?

Answer 29

Global - 49-60% marine genera 85% marine species

Question 30

What was the main cause of the Ordovician extinction?

Answer 30

Feedback created by the development of a continental ice sheet which expanded rapidly reducing sea level and removing shallow cratonic pools

Question 31

When were the 2 phase extinctions of the Ordovician?

Answer 31

1st End of Katian 2nd midway Hirnantian

Question 32

What are some examples of species greatly affected by the 1st extinction phase?

Answer 32

Chitinozoa Conodonts Graptolites Trilobites Brachiopods

Question 33

What are chitinozoa?

Answer 33

microscopic flask structures assigned to the zooplankton

Question 34

What are conodonts?

Answer 34

primitive vertebrates Largely known from their tooth- like feeding structures some thought to be pelagic, some swimming close to sea-floor (nekto-benthonic)

Question 35

What was the effect of the end Oreo on graptolites?

Answer 35

Major reduction in graptolites, but already in decline from earlier in the Ordovician

Question 36

How are trilobites affected by end Ordo?

Answer 36

pretty much all the free-swimming trilobites, such as Opipeuterella and the cyclopygids go in the first strike

Question 37

How are benthic assemblage zones and end Ordovician extinction linked?

Answer 37

1st strike sea level decline causing compression of sections 4 and 5 (shelf area) 2nd strike upward compression of segments