Week 2

Question 1

Stratigraphy =

Answer 1

Study of vertical sequence of strata and lateral variations of individual beds on a regional basin

• stratum
• bedding planes (bounding surfaces)

Question 2

Sharp boundaries represent

Answer 2

Period of non-deposition

Question 3

Lithostratigraphy =

Answer 3

Study of PHYSICAL relationship among rock units

Question 4

Biostratigraphy (concept)

Answer 4

:) Shorter lifespan = more precisely correlated
:) Rapidly evolving
:) Broad distribution

e.g. Graptolites, lower Palaeozoic correlate to 100,000 year time frame

Question 5

Chemostratigraphy (concept)

Answer 5

U/Th/K

Gamma rays, consistent with certain lithologies
- low for sand, high for mud

Question 6

Allostratigraphy =

Answer 6

Uses discontinuities:

• unconformities
• omission surfaces
• ravinement surfaces
• flooding surfaces

Question 7

Ravinement surface =

Answer 7

Erosional!

1st surface due to flooding (increasing SL)

Question 8

Flooding surface =

Answer 8

Separates young/old and obvious change in SL

Question 9

Facies =

Answer 9

Distinctive packet of sedimentary rock with specific sedimentary features FROM DEPOSITIONAL ENVIRONMENT

e.g. “deltaic” facies

Question 10

Lithofacies =

Answer 10

Based on grain size/mineralogy

Question 11

Biofacies =

Answer 11

Based on fossils

Question 12

Walthers Law =

Answer 12

Concept that vertical succession of facies represents lateral changes in environment

Question 13

What controls accommodation space?

Answer 13

SEA SURFACE
- eustasy = global SL from datum

SEA FLOOR
- tectonics

RATE OF SEDIMENT ACC

Question 14

Sea level falls =

Answer 14

Sea cuts down and incises
Regression
Coarsening upwards/prograding sequence

Foreshore material steps over and works its way towards the sea

Question 15

Sea level rises =

Answer 15

Sediment deposited further up near river
Transgression
Fining upwards sequence

Question 16

Mechanisms of SL change

Answer 16

Varying ice volume (global/regional)

Varying ridge volume

• slow spreading = decrease (steeper = more vol so requires “more sea”
• fast spreading = increases

Tectonic effects

• plate convergence
• continental collision

Question 17

Systems tracts =

Answer 17

Heterogeneous sedimentary units produced by contemporaneous depositional systems during specific phases of basal level variation

Question 18

TST

Answer 18

Transgressive

Increase in SL

Question 19

RST

Answer 19

Regressive

Decrease in SL

Question 20

Parasequence =

Answer 20

~conformable succession of genetically related beds/bedsets bounded by marine flooding surfaces and their correlative surfaces

Together form a sequence with unconformities as boundaries

Question 21

Progradational parasequence

Answer 21

Decreasing SL

Question 22

Aggradational parasequence

Answer 22

Static SL

Question 23

Retrogradational parasequence

Answer 23

Increasing SL

Question 24

Subaerial unconformity =

Answer 24

Formed through subaerial exposure and erosion including downcutting rivers/soil/karst processes

Question 25

Allocyclic controls =

Answer 25

External to system TECTONICS CLIMATE BASE LEVEL

Question 26

Allocyclic TECTONICS

Answer 26

Accommodation space Sediment flux direction Uplift = erosion Slope/stream power Facies distribution

Question 27

Allocyclic CLIMATE

Answer 27

Weathering Rainfall Glaciation Climatic belts (arid/tropical etc)

Question 28

GR: even block with sharp top and base "cylindrical"

Answer 28

Aggrading ``` Eolian Braided fluvial Channel fill Submarine-canyon fill Carbonate shelf margin Evaporite fill of basin ```

Question 29

GR: coarse up and sharp top "funnel"

Answer 29

Prograding ``` Crevasse splay River mouth bar Delta front Shoreface Submarine fan lobe Change from clastic to carbonates ```

Question 30

GR: fine up and sharp base "bell"

Answer 30

Retrograding ``` Fluvial point bar Tidal point bar Deep-tidal channel fill Tidal flat Transgressive shelf ```

Question 31

GR: hourglass "symmetrical"

Answer 31

Prograding and retrograding Reworked offshore bar Regressive to transgressive shore face delta

Question 32

GR: saw teeth "serrated"

Answer 32

Aggrading Fluvial floodplain Storm-dominated shelf Distal deep-marine slope

Question 33

When does a greater occurrence of turbidites in deepwater occur?

Answer 33

During lowstand rather than highstand