C-Mass Extinctions P2

Question 1

What are the alternative hypotheses to a bolide impact for the K-T boundary? (3)

Answer 1

Eustatic sea level changes
Climate changes
Volcanic eruptions

Question 2

Name the 3 boundaries and the large basalt provinces related to them.

Answer 2

T-J boundary: Central Atlantic Magmatic Province
K-T boundary: Deccan Traps
P-T boundary: Siberian Traps
Continental = flood basalts Oceanic = Plateaus

Question 3

Deccan Traps ((5)

Answer 3

In India
Multiple episodes of flood basalt
Fine-grained; volcanic; effusive
2km thick: 500,000km(squared): 512,000km(cubed)
Formed at K-T boundary

Question 4

In relation to the Deccan Traps, what is unusual about the size?

Answer 4

They were originally larger (India was beside Africa at time of eruption)

Question 5

What are the potential effects of the release of volcanic gases into the atmosphere? (CO2) (4)

Answer 5

CO2 emissions - global warming - Oceanic stagnation and marine anoxia - marine mass extinction

Question 6

What are the potential effects of the release of volcanic gases into the atmosphere? (Cl, F) (4)

Answer 6

Cl, F emissions - Acid rain - Fungal proliferation - Terrerstrial mass extinction

Question 7

What are the potential effects of the release of volcanic gases into the atmosphere? (SO2) (5)

Answer 7

SO2 emission - Brief global cooling - Glaciation - Sea-level fall - Marine mass extinction

Question 8

What re the geological events around the K-T boundary? (4)

Answer 8

Bolide impact at/near boundary
Deccan Traps eruption
Fall then rise in eustatic sea level
Warming then Cooling episode

Question 9

What is the input from the fossil record about the K-T boundary?

Answer 9

Faunal change across K-T boundary

Recent foraminifer: chambered shell of microscopic unicellular animal

Question 10

Input from fossil record: extinction patterns in fossil record (3)

Answer 10

Abrupt, Stepwise, Gradual

Question 11

Input from fossil record: brachiopods (4)

Answer 11

Shells
Denmark
Lazarus Taxa
Abrupt extinction at K-T boundary followed by origination of numerous new species

Question 12

Input from fossil record: planktic foraminifera (2)

Answer 12

El Kef, Tunisia

Step-like (Stepwise) extinction around K-T boundary followed by protracted origination of new species

Question 13

Input from fossil record: foraminifera (3)

Answer 13

Brazos river section, Texas
Extinction below and above K-T boundary, not at it
Tsunami depostits below K-T boundary?

Question 14

Input from fossil record: megaflora (3)

Answer 14

Marmath, North Dakota
Complicated pattern (gradual and stepwise)
Not all extinction at boundary

Question 15

Selective extinction - why did the dinosaurs go extinct but the likes of snakes, turtles, lizards and crocodiles didn’t?

Answer 15

Various groups are more affected than others despite similar ecologies
Eg. snakes, lizards, etc are smaller than dinosaurs so need less food, light, less chance of being found etc.

Question 16

Dinosaur Abundance - 2 interpretations

Answer 16

Hell Creek Formation

1) Extinction gradual over 8 mil years, then abrupt before K-T boudnary, therefore, extinct before K-T
2) Abrupt extinction at K-T boundary associated with an impact

Question 17

What are the problems with identifying extinction events? (5)

Answer 17

Sedimentary hiatuses
Signor-Lipps effect backsmearing
Fluctuating abundance
Lazarus taxa outage
Elvis taxa

Question 18

What are the problems with identifying extinction events? - sedimentary hiatuses (3)

Answer 18

Non-continuous deposition has effect of truncating fossil record
A gradual extinction event is preserved with signature of an abrupt event
Appears as dotted line in extinction graph

Question 19

What are the problems with identifying extinction events? - Signor-Lipps effect backsmearing (3)

Answer 19

Unlikely for LAD to be coincident with actual time of extinction (no matter how fine the sampling)
Effect is to artificially truncate a species range : backsmearing : any abrupt event appears more gradual than it is
Dot = last, line after = fossils preserved but not collected by sampling programme

Question 20

What does LAD stand for?

Answer 20

Last appearance datum

Question 21

What are the problems with identifying extinction events? - fluctuating abundance (2)

Answer 21

Sample: only a proportion of standing crop : likelihood of being included in the sample is a function of abundance
Presence of species fluctuates but is still there

Question 22

What are the problems with identifying extinction events? - Lazarus Taxa (2)

Answer 22

Can indicate local extinction then resupply from elsewhere

Can indicate migration of taxon from area and later return (migration could be related to: environmental conditions)

Question 23

What is Lazarus Taxa?

Answer 23

A taxon that disappears from the fossil record for an interval of geological time but appears again later

Question 24

Give an example of Lazarus Taxa.

Answer 24

Brachiopods, NW Europe, Denmark

Question 25

What are the problems with identifying extinction events? - Elvis Taxa (3)

Answer 25

Extinction event occurs
New taxa (sourced from taxon closely related to those that went extinct) evolve to fill vacant ecological niches
Anatomy may mimic that of the extinct species, leading to interpretation that original taxa are still present

Question 26

Conclusions of all mass extinction evidence to do with K-T boundary (

Answer 26

Can test if K-T event is result of bolide impact (should be abrupt extinction pattern in fossil evidence)
Fossil evidence does not consistently show abrupt extinction patterns
Fossil record could be compromised - so not accurate
Alternatively, bolide impact not event that caused mass extinction - other factors may have helped

Question 27

The 6th mass extinction

Answer 27

Earth currently experiencing many of the killing mechanisms invoked for terrestrial causes of extinction events
Could be 1st mass extinction to have anthropogenic causes

Question 28

What is a polymorph of calcium carbonate?

Answer 28

Aragonite

Question 29

Graptolite periderm is described as?

Answer 29

A recalcitrant organic tissue

Question 30

What evidence of he K-T boundary was furtherst from the crater impact (widest geographic distribution)? (7)

Answer 30

Boundary clay
Tektites
Stishovite
Ir anomaly
Fern Spike
Shocked quartz
Impact glass

Question 31

What is the taxonomic level and geochronological division used to identify mass extinctions?

Answer 31

Family period