04 - Stratigraphy 2.pdf

8/11/2019 04 - Stratigraphy 2.pdf

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STRATIGRAPHY 2Sediments in TIME and SPACE

http://www.eos.ubc.ca/courses/eosc326/content/EOSC326/

ID: eosc326

PW: ammonite

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LECTURE OUTLINE#

LITHOSTRATIGRAPHIC FORMATIONS

# FACIES

#

FACIES AND SEA LEVEL CHANGE# CASE 1: Stead State

# CASE 2: Transgression

#

CASE 3: Regression# Facies as Diachronous units

# WALTHERS LAW

#

MECHANISMS OF SEA LEVEL CHANGE# Crustal Deformation

# Isostatic Redress

# Global Eustatic Effects

#

Glaciation# Spreading Ridge Activity

# ENVIRONMENTS WHERE DEPOSITION OCCURS

#


3/43

MID TERM 1 HEADS UP

!"#$%&"' )*+$%$,-

./ !01234 . 561 77/ 8094:0;< ;451=6>? .@ 7 561 A/

A/ "3BC02>C BC4 D;4E;451=6>? :=33 60B F4 4G59=641

1=;4HB3I I02 5;4 ?J33 4GD4HB41 B0 F4 K59=3=5; :=BC

BC4 95B4;=53 D;4?46B41 =6 BC49/

$


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Learning Goals

1.# Define a lithostratigraphic formation

2.# Define a sedimentary facies and and explain how they may differ

laterally

3.#

Predict how facies will change vertically in response to sea levelrise (transgression) and fall (regression)

4.# Define Walthers Law

5.# List mechanisms of global (eustatic) and local sea level change.

6.# Relate sedimentary environmentsto the types of sediments

deposited in those environments and how this all relates to EarthSystem Science.

%


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Distinctive rock unit thathas recognizable contactswith units above and

below.

Rock type / fossilscontent / sedimentary

structures

ALSO must be able totrace it across country must be able to MAP it

Lithostratigraphic Formations

&


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Formations: 1 rocktype orassociations of

rock type, eg

Uinta Formation, Utah: composed of Sand and Siltstones

'


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How many formations would you tentatively identify?Mark them on the LHS of this photograph

The Grand Canyon (


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i>clicker: How many formations did you identify?

The Grand Canyon

A: 2

B: 3

C: 5

D: 6

E: 7

)


9/43

LithostratigraphicFormations in the

Grand Canyon

At least 10in this

part..

probablymore

noteGroup

*


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REMEMBER: A sediment is deposited as a factor of theenvironment in which it is being deposited

EG: Near shore sands deposited by a slow advancing sea.

NOTE: although this is all the SAME TYPE OF SEDIMENT the

sediments at A were deposited BEFORE the sediments at B

!+

L*#$ M*% 7N.A- L441 B0 4GD35=6 BC=? ?3=14? F4O4;


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Develops concept of Formations a little further

Facies: part of a rock body that has characteristics from which

we can infer the depositional environment.

Consider this EXAMPLE of where sediment is beingdeposited.

FACIES: A DefinitionSee page 102 106 for additional information

!!

reverse engineer what the sediments make up this rock

sand closest to shore. heaviest. currents cant carry them further out Carbonates:sediment produced by plankton


12/43

Turbulent (waves)High Energy

Environment

RIVER INPUT

All clasticsediments

have been

deposited

All coarsesedimentshave been

deposited

A coccolithophore: justone type of CaCO3

secreting planktonic

creature

Again in a little more detail..

Non clastic, biological sediment composedof CaCO3 Low Energy Environment

NOTE: this slope is greatly exaggerated!#

key to unravel ancient system because of the course -> fine sediment deposition


13/43


14/43

=PH3=H2;4T

=/# #2;F2346H4 0K :5B4;

==/#

U=V4 0K ?41=946B5;I >;5=6?===/

#

W=030>I

=R/#

Q5B4; 14DBC

R/# Q5B4; B49D4;5B2;4

SandMud and Clay

Carbonate mud

River:input of sediment

ShorelineSea level

"/# =/ ==/ =R/ R/

W/#

=/ ==/ ===/ =R/)/# =/ ==/ =R/

,/# ===/ =R/ R/

$/# ===/ =R/

!%

answer C


15/43

HOWEVER:Lets complicate things

Plot sea level versus time:

Facies SHIFT through timedue to changes in sea level

LOCAL and GLOBAL

(Global = Eustatic)

Facies and

Sea LevelChange

COD-XX46/:=X:=


16/43

CASE 1: the rate at which sediments are deposited keeps pacewith any changes in sea level T1 T3

RIVERINPUT

Facies boundaries inabout the same

location over time

TIME

Shoreline doesntchange location

A

A

Pebbles/GravelSand

SiltMuddy

carbonates

- facies boundaries and the location of the shoreline will notchange location over time

!'

no relative change in sea level, so the facies boundaries didnt really change


17/43

We often can not see a cross section with all the facies exposed.

Just have a thin core of sediment in order to work out how sea

level has changed in the past

COD-XX46/:=X:=ZQ4?B4;6Z"2?B;53=5/[D> COD-XX46/:=X:=

!(


18/43

T1

T2

T3

If you were to extract acore of sediments from

the area indicated in

case 1 at A A, this is

what that sedimentary

core would look likethe SAME facies from

the bottom to the top ofthe core.

A

A

As the sedimentary faciesare THE SAME over time

from the bottom of the

core (oldest) to the top of

the core (youngest) thenthe environmentalconditions (sea level)

MUST HAVE BEEN THE

SAME OVER TIME

Top of thesedimentary

core (youngest)

Bottom of thesedimentary core

(oldest)

!)

T1(oldest) and T3(youngest)

were sand, so it tells us the environment/sea level did not change

that much


19/43

CASE 2: Sea Level RISES over time: A TRANSGRESSION

- Facies MIGRATE in direction of ADVANCING shore line

Shore lineat Time-rock unit B

Shore lineat Time-rock unit A

Shore lineat Time-rock unit C

!*

environment is varying


20/43

NOTE the core of sediments you would get in this case

Progressively finersediments: Finer faciesOVERLY coarse facies:

SEA LEVEL MUST BE

RISING. Facies are saidto demonstrateonlappingbehaviour

Shore line A

Shore line B

Shore line C

#+


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CASE 3: Sea Level FALLS over time: A REGRESSION

- Facies migrate in direction of RETREATING shoreline

Progressively coarse

sediments: Coarse faciesOVERLY fine facies: SEA

LEVEL MUST BEFALLING. Facies

demonstratebacksteppingbehaviour

- NOTE the core of sediments you would get in this case

Oldest

shore line

Old shore

line

Current shore line

#!


22/43

=PH3=H ?B5B4946B? 95I F4 B;24 T

"/# #C=? 5;45 C51 F446 4GD4;=46H=6> ?45 34R43 ;=?4

W/#

#C=? 5;45 C51 F446 4GD4;=46H=6> ?45 34R43 K533

)/#

#C=? 5;45 C51 ?446 ?446 60 ;435JR4 HC56>4 =6 ?45 34R43,/# #C4 0H456 C51 F446 H06?=?B46B3I B2;F2346B \C=>C 464;>I]

BC;02>C02B BC4 J94 0K 14D0?=J06 0K BC4 ?41=946B

$/# #C4 0H456 C51 F446 H06?=?B46B3I ^2=4B \30: 464;>I]

BC;02>C02B BC4 J94 0K 14D0?=J06 0K BC4 ?41=946B

L*#$- ?30D4 C4;4 =? _%$"#'` 4G5>>4;5B41

#0D 0K H0;4

W0O09 0K H0;4

)5;F065B4?

U=3B?

U561?

)35I

##

answer B


23/43

Key

Pebbles/GravelSandSiltCarbonate

mud

Increasing grain size

Existingland

surface

Sea Level

Input ofsediment

Facies as Diachronous unitsDiachronus = time crossing

Example: with sea level rise

Shore lineT1

NOTE TIMEHORIZON T1

NOTE: Slope GREATLY exaggerated

#$


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Key


mud


Existingland

surface

Sea Level

Input ofsediment

Shore lineT1

NOTE TIMEHORIZON T1

#%


25/43

Sea Level

Input ofsedimentShore line

T2Shore line

T1

Movement of shoreline: TRANSGRESSION

As Before:- sea level rises

- facies migrate in the

direction of the moving

shoreline.

NOTE TIMEHORIZON T2

Key


mud


Existingland

surface#&


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Sea Level

Input ofsediment

Shore lineT2

Shore lineT1

Shore lineT3

- Sea level continuesto rise.


NOTE TIMEHORIZON T3

Key


mud


Existingland

surface#'


27/43

Sea Level

Input ofsediment

Shore lineT2

Shore lineT1

Shore lineT3

Shore lineToday


Boundariesbetween differentsea floors.. T1-T3

Effectively time

horizons (red)

Boundariesbetween

different facies

(yellow)

If we just correlated the same sediment TYPE (faciesboundaries. The yellow lines) we would be CROSS

CUTTING the red time lines (T1, T2, T3)

#(


28/43

On this diagram draw thefacies boundaries and time

lines .

Movement of shoreline: Transgression or regression?

NOTE: Slope GREATLY exaggerated

Key


mud


Existingland

surface#)


29/43

Indicate with an X theyoungest conglomerate.Indicate with a Y the

oldest carbonate.

Movement of shoreline: REGRESSION

facies

time

Key


mud


Existingland

surface#*


30/43

=PH3=H B0 ;435JR4 ?45

34R43 5? ;4D;4?46B41 FI BC=? S>2;4T \5??294 K5H=4?

F02615;=4? 5;4 R4;JH53]/

=/# %435JR4 ?45 34R43 =? K533=6>

==/#

%435JR4 ?45 34R43 =? ;=?=6>===/# U41=946B =6D2B =? D5H4 :=BC

?45 34R43 HC56>4

=R/# U41=946B =6D2B =? 60B D5H4

:=BC ?45 34R43 HC56>4

R/#

%435JR4 ?45 34R43 =? H06?B56B

SandMud and Clay

Carbonate mud


ShorelineSea level

"/#

=/ ===/ R/W/# =/ =R/

)/# ==/ =R/

,/# =/ ===/

$/#

===/ R/$+

answer Ebecause facies boundary

are vertical


31/43

=PH3=H :C5B :0231 F4 BC4

0;=46B5J06 0K BC4 K5H=4? F02615;=4?T

SandMud and Clay

Carbonate mud


ShorelineSea level

"/# M;09 34a B0 ;=>CB

W/#

#0:5;1? 144D4; :5B4;

)/#

M;09 ;=>CB B0 34a

,/#

W02615;I 0;=46B5J06 :0231 F4 R5;=5F34

$/#

M5H=4? F02615;=4? :0231 F4 R4;JH53

$!

answer A.


32/43

SO WHAT IS ALL THIS LEADING TO?

We know the following facts:

1.# Facies are distributed due to changing conditions of deposition

over the surface of our planet. In our example, shallow highenergy, near shore conditions are characterized by sand.Deeper, quieter conditions are characterized by finer grained

sediments.

2.#

As conditions change (such as sea level) facies will appear toMIGRATE, following their particular environmental conditions.

3.# Over time this will lead to patterns of facies as one facies

MIGRATES OVER ANOTHER.

Walthers Law

$#


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4. This means that when we recover a verticalsuccession of rock (like the one we used in our

example) we can PREDICT the lateral equivalenceof facies

As we go from coarse, near-shore facies at thebottomof the core to off-shore, deeper water

carbonate sediments at the topof the core, sealevel (in this example) must have been RISING over

time.

silts sands Conglomerates

silts

sandscarbonates

carbonates

silts sandscarbonates pebbles

sands

silts

Carbon-ates

bottom

top

The uneven boundaries between the facies arean attempt to demonstrate that facies GRADE

into each other just as environments grade into

each other.

Conglomerates

Conglomerates

$$


34/43

This is summed up in WALTHERS LAW

Facies that occur in a CONFORMABLE VERTICALSUCCESSION of strata, were deposited in laterally adjacent

depositional environments.

or put another wayadjacent sedimentary environments (facies) will end up

overlapping one another over time.

Sealevelfa

ll

Sealevelrise

Shore line

Beachsediments

Near shoresediments

Off shoresediments

$%


35/43

1. Crustal Deformation (Local)

# Mountain building

# Subduction

#

Continental collision

Mechanisms of Sea Level Change

(i.e. relative sea level)

$&


36/43

2. Isostatic redress (local)

# E.g. Removing ice sheets from Scotland

#

Scotland relative regression, England relative transgression

$'

ocean crust sag down because ice too heavy


37/43

Scotland: Raised BeachesEngland: Big Trouble!

Depositing lots of sediment can also cause the crust to sag

COD-XX46/:=X:=


38/43

The Michigan Basin

E#bcNN9 BC=H< =6 BC4 H46B;4

E#,4D0?=J06 K;09 )59F;=56 E d2;5??=H

$)

too much sediments deposited that the crust

sags

positive feedback. getting heavier, causing

more sag, causing more .


39/43

3. Global Eustatic Controls

1. Glaciation

$*

ice sheet grew, sea level sink.

sea level rise, ice sheet smaller


40/43

2. Spreading Ridge Activity

# Active spreading - Large Ocean Ridges hot and buoyant

#

Displace ocean water

%+

a lot of activity will produce a lot of mountain change, also displace water out therefore higher sea levels.

global effect not local


41/43

Environments where deposition occurs

Terrestrial transitional Marine: see readings

%!

higher sea level affect how

river deposit sediments


42/43

=PH3=H

14D0?=B41 =6 BC4 ?2F95;=64 K56T

"/#

#C4;4 :0231 F4 60 HC56>4W/# #C4 ?41=946B? :0231 F4H094 H05;?4;

)/# #C4 ?41=946B? :0231 F4H094 S64;

,/#

#C4 ?41=946B? :0231 F4 90?B3I H09D0?41 0K K431?D5;

$/# #C4 ?41=946B? :0231 F4 4;0141/%#

answer c


43/43

"#$% &'()*+,- .,(-/+0 1$- *2&+'%$0%3

U45 34R43 HC56>4 :=33 4e4HB BC4 HC5;5HB4; 0K "'' K5H=4? F4=6> 14D0?=B41 =6

"'' ?41=946B5;I 46R=;06946B?

4%,56 /&7

"89:; "8 4?4"

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04 - Stratigraphy 2.pdf