Sequence Stratigraphy Flashcards

1
Q

What does it mean to say that facies are retrogradational?

A

If sea level rises faster than sediment is supplied, the coastline shifts landward: this is known as transgression and the pattern in the sediments is retrogradational

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2
Q

What is progradational?

A

If sediment is supplied to a coast where there is no (or relatively slow) sea‐level rise the coastline moves seaward: this is regression and the sediment pattern is progradational.

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3
Q

What is aggradational

A

A situation where the coastline stays in the same position for long periods of time is relatively unusual and requires a balance between relative sea‐level rise and sediment supply producing a pattern of aggradation in the sediments.

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4
Q

What is the maximum flooding surface?

A

When transgression ceases and the shoreline initially remains static and then starts to move seawards. It can be identifies by the furthest point of landward extent of the shore line

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5
Q

The maximum flooding surface divides which two system tracts?

A

Highstand and transgressive

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6
Q

What is a ravinement surface? How does it form?

A

surfaces of erosion formed during transgression, they form because high wave energy in the shallow water that floods over the land surface can result in erosion

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7
Q

What is a parasequence?

A

packages of beds deposited as a consequence of the creation of a small amount of accommodation that is then filled up by sediment.

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8
Q

What triggers the start of new parasequence

A

a facies shift from shallower to deeper water deposition

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9
Q

What is the surface called that divides two parasequences

A

flooding surface

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10
Q

What is the facies pattern within an individual parasequence?

A

progradational

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11
Q

What is the definition of “sequence stratigraphy

A

The study of the relationships between sea level changes and sedimentation

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12
Q

What forms the upper and lower boundaries of a sequence

A

An unconformity caused by erosion called a sequence boundary

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13
Q

What is transgression

A

During a relative sea‐level rise, the shoreline will move landward

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14
Q

What is regression

A

Movement of the shoreline seawards as a result of sedimentation occurring at the coast

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15
Q

What is forced regression

A

seaward movement that is due to a relative sea‐level fall

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16
Q

What is accommodation space?

A

Places where sediment will accumulate

17
Q

What three variables are responsible for changes in accommodation space?

A

tectonics, eustatic sea level (global level changes), and sediment supply

18
Q

Why is this area called the “Book Cliffs”?

A

The layered sandstone and shale resemble book pages

19
Q

What resource forms the basis for the local economy?

A

Coal

20
Q

What sedimentary structure is used to deduce the storm wave base?

A

Hummucky beds that indicate they were made during storm waves

21
Q

Describe what is meant by “sediment partitioning.

A

It is a method of sectioning off the various depositional systems present in an environment based off of water depth and sediment supply over time

22
Q

When evaluating the unit called the “panther tongue”, what evidence was interpreted for the case of a river dominated delta vs a wave dominated delta

A

Lack of hummucky beds, instead being unilaterally deposited, having seaward dipping clinoforms, overall low-bay geometry, indicating river dominated delta

23
Q

An incised (eroded) valley was discovered that indicated a sea level fall. The valley was
subsequently filled in with deposits from what environment? What geologic evidence supported the interpretation of this environment?

A

The valley was an estuary turned marine open conditions based on the wave patterns, bioturbation patterns, and and the sand sediments

24
Q

Across the canyon, another erosional surface was identified. Was it another sequence boundary

A

It was a incied valley fill therefore a sequence boundry

25
Q

What puts an end to the field work for the day

A
26
Q

How does the flooding surface differ between the distal and proximal parts of the coastal
environment?

A

Its non linear and is above shoreline

27
Q

How do we know that the plants that formed coal layers grew in situ?

A

Underlying beach deposits have pitted pot marks that indicate peat swamp