Geol2001 Short Answer Questions

Front 1

Which of the ‘big five’ mass extinctions resulted in 2nd level ecological disruptions without significantly effecting reef ecosystems?

Back 1

Cretaceous–Paleogene extinction event (K/T)

Front 2

On what scale do alpha, beta, and gamma diversity differ?

Back 2

A =single fossillocality or a single sample of fossils (Local)/(Habitat)

B = Regional/local = True

Y = Diversity of an entire landscape/oceanscape (Regional)/(Landscape)

*A & Y can be measured with a species count

*B = Uses A+Y to work out how strongly the habitats overlap.

Front 3

Which type of diversity is plotted in Sepkoski curves?

Back 3

Total Diversity

Front 4

Calculate Simpson’s evenness index for the following fossil community:(NOTE: The actual exam will contain different numbers!)

brachiopod A: 1 specimens

brachiopod B: 2 specimens

bryozoan A: 4 specimens

bryozoan B: 2 specimens

crinoid A: 1 specimen

Back 4

D = 0.0476

D=1-(∑n(n-1)

------------

N(N-1)

Front 5

How many Bambachian megaguilds are represented by the 5 species listed in the table below?

Back 5

4

1) A&B (Same Bambachian megaguild)

2) C

3) D

4) E

Front 6

In which geological period appear the first representatives of the Modern Evolutionary Fauna?

Back 6

End-permian mass extinction lead to a rise of MFs

Cambrian, rise in Triassic

Front 7

How did the diversity of the Palaeozoic Evolutionary Fauna develop during the Mesozoic?

Back 7

stenotopic organisms

Front 8

In the table below list the stratigraphic range (e.g. Ordovician – Permian) during which the groupslisted below were at the peak of their ecological success.

1)bivalves

2)inarticulate brachiopods

3)crinoids

Back 8

1)tria-terc

2)Cambrian

3)ord-dev

Front 9

9. Which quantitative method results in a plot as shown below?

y=N of species

x=N of Samples

Back 9

Rarefaction curve

Front 10

What is described by the Signor-Lipps effect?

Back 10

The first and last appearance of a fossil taxon is never truly known

Front 11

Define the term convergent evolution.

Back 11

Organisms that are not closely related adapt similar characteristics, due to environmental controls. Eg. Sharks(fish), Dolphins(mammals),

Front 12

To what substrate were crinoids with lots of arms and a long flexible stem likely attached?

Back 12

hard grounds

Front 13

In the diagram below mark the type of survivorship curve that is typical for a population oforganisms with an r-strategy.

y= N of survivors as a %

x= Age of species as a %

Back 13

Type 3

Because high infant mortality rate in r-strategists, so sharp decrease in survivors in early age

Front 14

Name two characteristics of K-strategists.

Back 14

Large body

slow to mature

few offspring

Tendency to occupy niches in systems which are already near or at population limit

Tend to occur in stable systems

Low juvenile mortality

Front 15

Name two characteristics of r-strategists.

Back 15

Fast to mature

High fecundity

High dispersal ratesmall body types

many offspring

Tend to occupy high stress/unstable environments

High juvenile mortality

Front 16

The base of which geological period is defined by the first appearance of an ichnospecies? (Burrowers)

Back 16

Base of the Cambrian period

Front 17

If burrow A cross-cuts burrow B, which burrow formed in a shallower tier?

Back 17

B

Front 18

What happens to burrow size as oxygen levels in the marine environment decrease?

Back 18

Decreases

Front 19

What is the name given to the study of fossil communities?

Back 19

Palaeosynecology

Front 20

What term is used to describe the sedimentary rock fabric caused by the activities of burrowing organisms?

Back 20

Bioturbation

Front 21

Give two examples of trace fossils that are underground miners:

(a):

(b):

Back 21

Fodinichnia & Agrichnia (Possibly) or diplocraterion & rhizocordlium

Front 22

Which ichnofacies indicates quiet, deep, muddy environments and is dominated by pascichnia andagrichnia?

Back 22

Nereites (Off shore/deep)

Front 23

Which ichnofacies indicates mobile, sandy substrates and is dominated by vertical domichnia?

Back 23

skolithos (Shoreface)

Front 24

What term is given to fossil taxa that temporarily disappear from the rock record, e.g. in theaftermath of extinction events?

Back 24

Lazarus taxon

Front 25

Which large igneous province is associated with the Late Triassic mass extinction event?

Back 25

central Atlantic magmatic province

Front 26

Name an important use of microfossils in geology?

Back 26

Dating (biostratigraphy)

Front 27

Give an example of a method used in the preparation of sediment samples for microfossil analysis?

Back 27

Dying, washing, chemical extraction, thin section analysis

Front 28

Name a microfossil group which has a calcareous shell?

Back 28

Foraminifera

Front 29

Name a microfossil group which has a siliceous shell?

Back 29

Siliceoflagellate

Front 30

Name a microfossil group which has an organic-walled shell?

Back 30

Dinoflagelattes

Front 31

The life cycle of foraminifera is characterised by an alternation between two generations – one that reproduces sexually and one that reproduces asexually. Name these 2 generations?

Back 31

Gamont (sexual) & agamont (asexual)

Front 32

In the classification of foraminifera, Loeblich and Tappan (1964) recognised 5 suborders. Name thesuborder of foraminifera which have imperforate, porcelaneous calcareous walls?

Back 32

Miliolina

Front 33

In the classification of foraminifera, Loeblich and Tappan (1964) recognised 5 suborders. Name thesuborder of foraminifera which have perforate, hyaline calcareous walls?

Back 33

Rotalinia

Front 34

In the classification of foraminifera, Loeblich and Tappan (1964) recognised 5 suborders. Name thesuborder of foraminifera that use foreign particles to make their tests and cement them together witheither organic or calcareous cements?

Back 34

Textulinia

Front 35

In the morphology of foraminifera, what term is used for the chamber arrangement where chambers are coiled in a helical spire?

Back 35

Trochospiral

Front 36

Name an abiotic environmental factor that controls the distribution and abundance of benthic foraminifera?

Back 36

Salinity

Temperature

Dissolved O2

Front 37

Name an important biotic environmental factor that controls the distribution and abundance ofbenthic foraminifera?

Back 37

Space

food

competiton

Front 38

In the study of modern foraminifera, what is the name of the non-vital stain that is commonly usedto differentiate ‘live’ from ‘dead’ individuals?

Back 38

Rose-bengal

Front 39

The proportions of three wall structures of foraminifera are commonly plotted on ternary diagramsto differentiate particularly shallow-water environments. Name these 3 wall structures?

Back 39

Hyaline

porcelaneous

agglutinated

Front 40

Name a diversity index that is commonly used in the study of benthic foraminifera?

Back 40

Fisher alpha index

Front 41

Larger foraminifera are said to be adapted to nutrient deficient conditions. What term is used fornutrient deficient conditions?

Back 41

Oligotrophic

Front 42

Give the name of a genus of larger foraminifera?

Back 42

Nummulite zenehesis

Front 43

Name an area on Earth where the environment is described as ‘hypersaline’?

Back 43

Arabian gulf

Front 44

Name a genus of benthic formaninifera that is typical of lagoon environments?

Back 44

Quincoequelina

Front 45

What morphological features are typically associated with benthic foraminifera that occupy an epifaunal microhabitat?

Back 45

Rounded trochospiral

Milioline biconvex

Front 46

Name two key morphological features of planktic foraminifera?

Back 46

Globular chambers & open appiture

Front 47

Name an important ecological factor that controls the distribution and abundance of planktic foraminifera?

Back 47

Temperature

Front 48

It is known that planktic foraminifera occupy different depths within the water column. Typically,what are the morphological characteristics of species that occupy surface waters?

Back 48

Smaller thinner walled

Symbiont bearing

Front 49

It is known that planktic foraminifera occupy different depths within the water column. Typically,what are the morphological characteristics of species that occupy deeper waters?

Back 49

Keeled

non spinose

thicker walled

Front 50

The coiling direction of the planktic foraminifera Neogloboquadrina is commonly used forreconstructing past water temperatures. Name the species that coils in an anticlockwise direction(left/sinistral) and dominates in colder waters?

Back 50

Neoglobquadrina pachyderma

Front 51

Cemented beach sands are common in which diagenetic environment?

Back 51

Marine Vadose

Front 52

Cements in modern beach rocks typically consist of which carbonate mineral?

Back 52

Aragonite or High-Mg calcite

Front 53

The formation of cemented beach sands typically occurs how far below the surface?

Back 53

10's of cm

Front 54

Microbial micritisation is common in which diagenetic environment?

Back 54

Marine phreatic (Quieterwater-low energy areas- back reef lagoons)

Front 55

Formation of grapestones and aggregates is common in which diagenetic environment?

Back 55

Meteoric Vadose

Front 56

Carbonate dissolution commonly occurs in which diagenetic environment?

Back 56

Meteoric

Front 57

What is the defining feature of isopachous cements?

Back 57

Equal all the way around the grain

Front 58

As rainwater is undersaturated with respect to CaCO3, this leads to which process?

Back 58

Dissolution

Front 59

As water moves downwards through the meteoric vadose zone via diffuse or conduit flow it become saturated in CaCO3 so that cementation occurs. These cements are typically what type of carbonate?

Back 59

Low mg-calcite

Front 60

Name a carbonate mineral that is highly susceptible to dissolution?

Back 60

Aragonite

Front 61

In arid settings what is the typical rate of alteration?

Back 61

Slow

Front 62

Ferroan cements contains elevated concentrations of which element?

Back 62

Iron (Fe+)

Front 63

Name an environment in which cementation takes place where CaCO3 enriched waters result from evaporation?

Back 63

Meteoric Vadose (Cave systems, desert wadi)

Front 64

With respect to carbonate diagenesis principle cements types include aragonite; high-Mg calcite;low-Mg calcite and dolomite.

Name a less common cement type associated with carbonate diagenesis?

Back 64

Quartz

Kaolinite

Gypsum

Halite (Salt)

Front 65

Slow and continuous cementation processes in the meteoric phreatic diagenetic environment leadto what type of cement morphologies?

Back 65

Large blocky spar

Front 66

Increasing ambient Mg/Ca supply combined with increasing carbonate ion supply typically leads to which cement morphology?

Back 66

Accicular

Front 67

In which latitudes is seawater supersaturated with respect to CaCO3 today?

Back 67

Tropics +/- 25 degrees

Front 68

What is the surname of the geologist who devised the Facies code system for fluvial deposits?

Back 68

Miall (1977)

Front 69

What does a sedimentary facies allow the interpretation of?

Back 69

Allows a sedimentary process to be established, based upon key descriptive attributes. I.e.

- Fluid (Air or water) or Gravitational deposition

- Planar Cross laminations etc.

- Coarsening/ fining up cycles

Front 70

What does a facies association allow the interpretation of?

Back 70

Assign all sediments to an environment ( Look for facies patterns in a log)

Front 71

Name a sedimentary process that is typical of alluvial fan environments?

Back 71

1) Debris Flow

2) Sheet Flood

3) Stream Channel

Front 72

In stratigraphy, what is the name of the law that describes the arrangement of sedimentary facies in space and time?

Back 72

Walther's Law - The principle that facies occur in conformable vertical successions of starta, also occur in laterally adjacent environments

Front 73

Name an environmental controlling factor that can result in the development of a coarsening or fining upwards facies sequence?

Back 73

Reduction in energy from a channel caused by warming of climate (Less precipitation) will cause a fining up sequence in river beds.

Vise versa

Repeated fault movements caused by tectonics increasing gradients causes coarsening upwards in alluvial fans.

Front 74

An alluvial fan with a low surface slope and a large catchment area will be dominated by what kind of sedimentary process?

Back 74

Sheet flood

Higher water supply

Low angle

Front 75

Name a facies model for an alluvial fan setting?

Back 75

The Trollheim Facies Model

or

Conceptual alluvial fan facies model by Miall (1977)

Front 76

An alluvial fan with a steep surface slope and a small catchment area will be dominated by what kind of sedimentary process?

Back 76

Debris flow

Low water supply

Steep slopes

Front 77

Meandering river channels can often undergo avulsion. Name a cut off process that results inavulsion?

Back 77

Neck cut-off

Front 78

Palaeosols in floodplain deposits that show grey mottling indicate what kind of climatic setting?

Back 78

Humid Climate

-Reduction mottling

- Gleys?

Front 79

What is a lake setting characterised by evaportic sediments called?

Back 79

Playa Lake

Front 80

The development of evaporitic minerals on a lake floor will result in the formation of what kind of surface cracks?

Back 80

Desiccation cracks

Front 81

What kind of basin fill geometry is formed within a symmetrical rift basin?

Back 81

Graben

Front 82

What kind of sedimentary environment characterises the footwall setting of a terrestrial rift basin?

Back 82

Alluvial fan

Front 83

The axis of an externally drained rift basin is dominated by what kind of sedimentary environment?

Back 83

Rivering environment (Fluvial)

Axial drainage channel

Front 84

What is the collective name of the sedimentary facies that develops within the underfilled stage offoreland basin development?

Back 84

Flysch (Fine)

Front 85

What is the collective name of the sedimentary facies that develops within the overfilled stage offoreland basin development?

Back 85

Molasse (Coarse)

Front 86

What are the main deltaic-sub environments?

Back 86

1) Delta Plain (Interdistributary bays & Distributary channels)

2) Delta Front (Proximal and Distal)

3) Prodelta

Front 87

What are the main sub-environments in a delta plain?

Back 87

Interdistributary bays (muds) & Distributary channels (Sands)

Front 88

What are names of the two processes which deliver sediment from distributary channels to interdistributaryareas?

Back 88

Overbank flooding

&

crevassing

Front 89

What kind of facies successions typify minor mouth bar progradation?

Back 89

Progradation = Coarsening Up successions

Front 90

What kind of dense flows deliver coarse sediment to the distal delta front and prodelta?

Back 90

Hyperpycnal (Turbidity currents)

- Effluent denser than basin waters

Front 91

Hypopycnal conditions are occur when?

Back 91

When effluent is less dense than basin water density, leading to effluence floating above basin water creating a salt wedge

Front 92

What is the key difference between failure-induced turbidites and hyperpycnal turbidites on deltafronts?

Back 92

Hyperpycnal is caused by denser effluent from channel entering a less dense basin.

Failure-induced is from slumping & slides along basal sheare zone, caused by tectonics, gas hydrate escape

Front 93

Normal regression in deltas generates what kind of facies succession?

Back 93

Progradation so coarsening up successions

Front 94

What sedimentary features are typical of delta front successions which are not found in offshoreshelf deposits?

Back 94

1) heterolithic Clinoforms <2°?

2) Higher Sand:Mud ratio Coarse deposited at mouth)

3) Wave reworked (offshore below mean storm wave base)

Front 95

Which type of sedimentary structure is unique to the offshore-transition zone?

Back 95

Storm-generated sand beds of laminated hummocky cross-stratification

Front 96

Palaeocurrent distributions from trough cross bedding deposited in the upper shoreface are likely toshow what kind of distribution?

Back 96

Parallel to palaeo shoreline

Front 97

The thickest successions in near-shore facies are likely to be deposited during what kind of genetic behaviour?

Back 97

Progradation

Front 98

What flow regime does parting lineation develop in?

Back 98

lower part of the upper flow regime

Front 99

What kind of genetic behaviour occurs when sediment supply rate in the nearshore zone is greaterthan the rate of relative sea-level rise?

Back 99

Normal Regression - Progradation

Front 100

How can erosion surfaces generated by regression and transgression be differentiated in nearshoresuccessions?

Back 100

Forced regression - Out-of-sequence shallowing & surface offorced regression

*Offlap w/ downstepping

Transgression - Ravinements (transgressive surfaces of erosion)

*Retrogradation w/ backstepping

Front 101

Forced Regression = Sea level fall (forced progradation)

Retrogradational = Sed. deficit & formation of barrier islands, estuaries ( *Flooding)

Back 101

Not a question