656
0
0
0 .2
E
0.4
6 0.6
I
I- 0.8
0...
w
0
...J
~
er
:::>
m
N
n, POROS ITY
0 .2
0.4
,'~, /' h1 = 1m
,'< (n1 = 0.7)
\
' ,
\ \ ' ,
-t
\
\ ' ,
I
\
\ \ z2
'. \ \ I
'. \ \ 1
\
, \
b
0 .6
SEDIMENT
COLUMN
\ I \ I
\ I \
\ I \
\ I
\ I
\2 3
: I
c-------/[i ]
\
COMPAC TI ON
Chapter 13 Diagenesis
COMPA CTION AND
COM PACTI ON RATI O
lI -
· a -- --f
POROSITY
I
I
h p
I
n1
SOLIDS
I
,
h1
7.; -
I
"2
I
I
1\-'h2
I
h s I
I
.i _ ~ _
I
:i. _
COMPACTI ON RATIO CR = hh 1 = 1 1 - "2
( 1)
2
- n1
2
"
I
\
h 1 = 400m
~DECOM PACTION
\ I (n1 = 0.55)
/
"
I
\
~
3-f-r-------- -llJ
SINCE hs = ( 1- "1 ) h1 =( 1- n2 ) h2 ,
HEIGHT OF PORE WATER LOSS:
I
\
I- - -
-r --- - , - --7
1
2
3
CR , COMPACTION RATIO
c
d
COMPACTlON
~
"
VOID RATIO e= hs"
e
(2)
(3)
SOLID PARTlCLE
SHALLOW ·BURIA L
(GRAVEL , FOSSIL)
CONCRETlON)
~~~i---~-~-~~~-----~~
- - -
- - - -
...... 1
_ _ _
_ _ _ _ _ _
laIif
_
- -- ------DIFFERENTIAL COMPACTION
SEDIMENT ·FILLED
PRIOR TO DISSOLUT ION OF SHELL
::!: INTACT
SHELL
Fig. 13.6. a Demonstration of compaction ratio, eR,
vOld ratio, e, and thickness or height of expelled pore
water by comparing two sedimentary columns. These
have the same height, h s ' of compact, solid matter,
but differing porosities, nj and n 2 • b Relationship
between porosity-depth curve and eR at different
depths, z, below top of sedimentary sequence. Note
that eR depends on the height, hj , of the uppermost
sediment column and on its average porosity, nj ,
which decreases with increasing thickness of h,.
c-e Direct measurement of compaction ratio using (c)
horizontal, initially cylindrical sediment-filled burrows, (d) compacted part of sediment-filled broken
fossil shell, and (e) initial parallellamination deformed by differential compaction adjacent to solid
gravel, compact fossil (e.g. belemnite, bone of vertebrae), and early diagenetic concretion
0
0
0 .2
E
0.4
6 0.6
I
I- 0.8
0...
w
0
...J
~
er
:::>
m
N
n, POROS ITY
0 .2
0.4
,'~, /' h1 = 1m
,'< (n1 = 0.7)
\
' ,
\ \ ' ,
-t
\
\ ' ,
I
\
\ \ z2
'. \ \ I
'. \ \ 1
\
, \
b
0 .6
SEDIMENT
COLUMN
\ I \ I
\ I \
\ I \
\ I
\ I
\2 3
: I
c-------/[i ]
\
COMPAC TI ON
Chapter 13 Diagenesis
COMPA CTION AND
COM PACTI ON RATI O
lI -
· a -- --f
POROSITY
I
I
h p
I
n1
SOLIDS
I
,
h1
7.; -
I
"2
I
I
1\-'h2
I
h s I
I
.i _ ~ _
I
:i. _
COMPACTI ON RATIO CR = hh 1 = 1 1 - "2
( 1)
2
- n1
2
"
I
\
h 1 = 400m
~DECOM PACTION
\ I (n1 = 0.55)
/
"
I
\
~
3-f-r-------- -llJ
SINCE hs = ( 1- "1 ) h1 =( 1- n2 ) h2 ,
HEIGHT OF PORE WATER LOSS:
I
\
I- - -
-r --- - , - --7
1
2
3
CR , COMPACTION RATIO
c
d
COMPACTlON
~
"
VOID RATIO e= hs"
e
(2)
(3)
SOLID PARTlCLE
SHALLOW ·BURIA L
(GRAVEL , FOSSIL)
CONCRETlON)
~~~i---~-~-~~~-----~~
- - -
- - - -
...... 1
_ _ _
_ _ _ _ _ _
laIif
_
- -- ------DIFFERENTIAL COMPACTION
SEDIMENT ·FILLED
PRIOR TO DISSOLUT ION OF SHELL
::!: INTACT
SHELL
Fig. 13.6. a Demonstration of compaction ratio, eR,
vOld ratio, e, and thickness or height of expelled pore
water by comparing two sedimentary columns. These
have the same height, h s ' of compact, solid matter,
but differing porosities, nj and n 2 • b Relationship
between porosity-depth curve and eR at different
depths, z, below top of sedimentary sequence. Note
that eR depends on the height, hj , of the uppermost
sediment column and on its average porosity, nj ,
which decreases with increasing thickness of h,.
c-e Direct measurement of compaction ratio using (c)
horizontal, initially cylindrical sediment-filled burrows, (d) compacted part of sediment-filled broken
fossil shell, and (e) initial parallellamination deformed by differential compaction adjacent to solid
gravel, compact fossil (e.g. belemnite, bone of vertebrae), and early diagenetic concretion