AN ABSTRACT OF THE THESIS OF
e E. Johnson Ibach
in
for the degree of
Oceanography
Title:
presented on
Master of Science
22 April 1980
THE RELATIONSHIP BETWEEN SEDIMENTATION RATE AND TOTAL ORGANIC
CARBON CONTENT IN ANCIENT MARINE SEDIMENTS
Abstract approved:
Redacted for Privacy
LaVerne Kuim Erwin Suess
Sedimentation rate could become a new exploration tool for evaluating the source rock potential of sedimentary basins in frontier regions.
Petroleum source rocks are defined on the basis of total organic carbon
by weight percent.
An analysis of Deep Sea Drilling Project (DSDP)
cores indicates that there exists quantitative relationships between
sedimentation rate and total organic carbon content in fine grained
ancient marine sediments of Jurassic, Cretaceous and Cenezoic age.
These relationships are independent of geographic setting, geologic age,
and differential compaction, but are highly dependent upon lithology.
For any given sedimentation rate, the total organic carbon content
increases from calcareous to siliceous to black shale sediments.
For
each of these lithologies, the total organic carbon content increases
with sedimentation rate due to reduced aerobic microbial degradation at
higher burial rates.
Above a critical sedimentation rate, the total
organic carbon content may decrease with increasing sedimentation rate
due to a clastic dilution effect.
Aerobic microbial degradation, how-
ever, continues to be less efficient at higher burial rates.
Therefore,
even though the total organic carbon content may decrease, the quality
of the organic matter preserved and the oil generation and oil migration
potential of the sediment may continue to increase with increasing
sedimentation rate.
Similar relationships have also been established between total
organic carbon and grain accumulation rate, and total organic carbon
accumulation rate and grain accumulation rate.
These relationships
support both reduced aerobic microbial degradation and the clastic
dilution effect.
In the latter case, the lithologic control is less
pronounced, and the relationship can be used to determine total organic
carbon content even when the lithology is not known.
The results of this study have important implications for petroleum
exploration in frontier regions.
Sedimentation rate and grain accumula-
tion rate could be determined from seismic isopach and velocity data.
When the lithology is not known, such as prior to exploration drilling,
grain accumulation rates could be used to estimate the total organic
carbon content, and the oil generation and oil migration potential of a
sedimentary basin.
Once the lithology is known, the source rock poten-
tial of the basin can be more accurately predicted.
Future work should
be directed toward testing the application of sedimentation rate and
grain accumulation rate in the petroleum exploration of frontier regions.
The Relationship Between Sedimentation Rate and
Total Organic Carbon Content in Ancient Marine Sediments
by
Lynne E. Johnson Ibach
A THESIS
submitted to
Oregon State University
in partial fulfillment of
the requirements for the
degree of
Master of Science
June 1980
APPROVED:
Redacted for Privacy
essor of Oceanography
in charge of major
Redacted for Privacy
Associate Professor of Oceanography
in charge of major
Redacted for Privacy
Dean of School of Oceanography
Redacted for Privacy
Dean of Grivate School
Date thesis is presented
22 April 1980
Typed by Pam Wegner for
Lynne E. Johnson Ibach
Dedication
To my Mother and Father, who inspired me and supported me throughout the course of my studies;
and
To my husband, Darrell, who was always there to listen and offer
suggestions when I most needed it.
Thank you.
Acknowledgements
I would like to give special thanks to my co-advisors, Dr. LaVerne
Kulm and Dr. Erwin Suess, for their continued support and guidance
during this study.
I would also like to thank Dr. Bill Hutson, Chi
Muratli and Duncan McEwan for their technical assistance on statistical
computer programming; Dr. Hans Schrader and Dr. Larry Small for biological discussions and references on the nature of primary productivity;
and Dr. Gunnar Bodvarsson and Dr. Steve Johnson for their advice on
geophysical aspects of this study.
I am also indebted to Peter Woodbury
and the Data Handling Section of the Deep Sea Drilling Project for their
informative help in retrieving the DSDP data on which this study was
based.
TABLE OF CONTENTS
Page
INTRODUCTION ...................................................
1
BACKGROUND.....................................................
2
PROCEDURE ......................................................
Samples...................................................
Lithology.................................................
Age.......................................................
Sedimentation Rate ........................................
Total Organic Carbon ......................................
Accumulation Rates ........................................
Graphical and Statistical Analysis ........................
3
RESULTS AND DISCUSSION .........................................
Effect of Environmental Setting and Geologic Age
..........
Effect of Lithology .......................................
Lithologic Effect on Total Organic Carbon Content ...
Lithologic Effect on the Relationship Between
Sedimentation Rate and Total Organic Carbon
Content............................................
Low Rate of Sedimentation:
Increasing Organic
Carbon Content ................................
High Rate of Sedimentation: Decreasing Organic
Carbon Content ................................
3
5
5
6
6
7
7
8
9
9
12
14
14
20
Effect of Differential Compaction .........................
23
Relationship Between Organic Carbon Content Versus Grain
Accumulation Rate and Organic Carbon Accumulation Rate
Versus Grain Accumulation Rate ..........................
27
Lithologic Effect on Organic Carbon Accumulation Rate
.....
31
IMPLICATIONS FOR PETROLEUM EXPLORATION .........................
32
CONCLUSIONS ....................................................
36
REFERENCES .....................................................
39
APPENDIX I:
Summation of Data for DSDP Sediment Intervals
.....
43
LIST OF FIGURES
Figure
Page
1
Location of Deep Sea Drilling Project (DSDP) Holes.
2
Organic Carbon Versus Sedimentation Rate Showing
Environment of Deposition and Geologic Age.
10
3
Organic Carbon Versus Sedimentation Rate Showing
Lithologic Field Zonation.
11
4
Low
Organic Carbon Versus Sedimentation Rate.
rates of sedimentation are characterized by
High rates of
increasing organic carbon content.
sedimentation are characterized by decreasing organic
carbon content.
15
5
Effect of Sedimentation Rate on the Degradation of
Organic Matter.
18
6
Organic Carbon Versus Sedimentation Rate in Recent
Sediments.
19
7
Relationship Between Sedimentation Rate, Organic
Carbon Content and Primary Productivity for Recent
Marine Sediments.
22
8
Organic Carbon Versus Grain Accumulation Rate Showing
Lithologic Fields in the Absence of Differential
Compaction Effects.
24
9
Low
Organic Carbon Versus Grain Accumulation Rate.
rates of grain accumulation are characterized by
increasing organic carbon content. High rates of
grain accumulation are characterized by decreasing
organic carbon content.
25
10
Organic Carbon Accumulation Rate Versus Grain
Accumulation Rate Showing the Contraction of
Lithologic Fields.
28
11
Organic Carbon Accumulation Rate Versus Grain
Low rates of grain accumulation
Accumulation Rate.
are characterized by increasing rate of organic
High rates of grain accumulation
carbon accumulation.
are characterized by a slower increase in the rate of
organic carbon accumulation.
29
12
Organic Carbon Accumulation Rate Versus Grain
Accumulation Rate without Lithologic Field Zonation.
33
13
Sonic Velocity Versus Grain Density.
35
4
LIST OF TABLES
Page
Table
Organic Carbon Versus Sedimentation Rate.
Mathematical Expression and Statistical
Correlation (R) for Each Lithology.
16
2
Organic Carbon Versus Grain Accumulation Rate.
Mathematical Expression and Statistical
Correlation (R) for Each Lithology.
26
3
Organic Carbon Accumulation Rate Versus Grain
Accumulation Rate. Mathematical Expression and
Statistical Correlation (R) for Each Lithology.
30
1
THE RELATIONSHIP BETWEEN SEDIMENTATION RATE AND
TOTAL ORGANIC CARBON CONTENT IN ANCIENT MARINE SEDIMENTS
INTRODUCTION
The hydrocarbon potential of a sedimentary basin depends in part on
the presence of favorable petroleum source rocks.
One of the major
problems in petroleum exploration is establishing criteria that can
evaluate the source rock potential of both onshore and offshore basins
in frontier regions.
Petroleum source rocks are defined on the basis of total organic
carbon content.
Clastic source rocks contain at least 0.5% total organ-
ic carbon by weight while carbonate source rocks contain at least 0.3%
total organic carbon by weight (Tissot, 1978).
These limits represent
the minimum organic carbon content required for oil migration to occur
under favorable maturation conditions.
The petroleum generating poten-
tial of a source rock can be evaluated by determining the organic content of the sediments, the volume of organic rich sediments, the nature
of the organic constituents (oil-prone marine versus gas-prone terrestrial) and the degree of thermal maturation of the sediment.
At present, the evaluation of petroleum source rock requires criteria that can be applied only to areas with extensive well control.
New criteria now need to be developed for frontier basins where there is
limited well control and petroleum exploration depends largely on the
analysis of seismic reflection records.
These new criteria should be
based on factors such as rate of sedimentation, which can be determined
from seismic reflection records prior to exploration drilling (Vail et
al., 1977).
2
The purpose of this study was to establish whether sedimentation
rate could be used to define the total organic carbon content or source
rock potential of ancient marine sediments.
The specific objectives
were to determine 1) if a quantitative relationship exists between
sedimentation rate and total organic carbon content in fine grained
ancient marine sediments and 2) the effect of variable lithology, age,
environmental setting and differential compaction on the observed relationship.
If a relationship between sedimentation rate and organic carbon
content can be established, sedimentation rate could be used to identify
source rock facies from seismic reflection records of marine sedimentary
basins.
Furthermore, the petroleum generating potential of the source
rock could be estimated from seismic records by determining the volume
and burial history (thermal maturation) of the marine source rock facies.
BAC KG ROUND
Until recently, organic rich sediments were thought to be preserved
only in lakes and basins with restricted circulation (Blatt, Middleton
and Murray, 1972).
However, numerous recent studies document the pre-
servation of organic-rich sediments on continental margins and in offshore basins under open marine conditions.
These organic sediments are
rich in primary marine organic constituents (i.e. phytoplankton) and are
more oil prone than sediments rich in terrestrial organic constituents
at the same level of thermal maturation (Tissot, 1978).
Numerous studies
by such authors at Gross et al. (1972), Romankovich (1968), Bordovskiiy
(1965) and Trask (1934) have observed that organic content of these
sediments varies with certain parameters.
The organic content is higher
3
the sediments are fine grained (silts and clays); the sedimenta-
when:
tion rate is higher; the sediments are associated with high primary
productivity regions; and when the sediments are known or inferred to
have formed under oxygen deficient conditions.
More recent studies by Heath et al. (1977) and MUller and Suess
(1979) have defined a relationship between organic carbon content and
sedimentation rate for fine grained sediments in modern environments.
These studies show that the organic content of recent sediments increases quantitatively with sedimentation rate.
Sedimentation rate is critical because it controls the degree of
preservation or organic matter in recent sediments.
MUller and Suess
(1979) have shown that as the sedimentation rate increases, there is a
higher percentage of the primary productivity of a region preserved in
the bottom sediments.
Coleman,. Curtis and Irwin (1979) indicate that
rapid rates of burial shorten the duration of aerobic microbial degradaLess microbial degradation results in a higher content of organic
tion.
carbon preserved, more oil prone organic constituents, and less CaCO3
diagenic cements which would inhibit oil migration.
PROCEDURE
Samples
The study utilized selected cores from the broad data base of drill
hole material obtained by the Deep Sea Drilling Project (DSDP).
One
hundred and five sediment intervals were chosen from 38 DSDP cores so as
to represent a wide range of environments of deposition (Figure 1).
sediment intervals chosen reflect:
The
inland sea; marginal back arc basin;
active, passive and translational continental margins; and deep ocean
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Location of I)eep Sea Drilling Project (DSDP) Holes.
I:
4Q 50
5
basin environments.
They include sediments of Jurassic, Cretaceous,
Tertiary and Pleistocene age and each sediment interval reflects the
deposition of a distinct lithology such as "black shale," silty clay and
diatomite (siliceous), and nanno fossil ooze (calcareous).
The lithol-
ogy, age, sedimentation rate, total organic carbon content, bulk density,
porosity and accumulation rates of the sediment intervals are given in
Appendix I.
Litho logy
Lithologic descriptions were made by the shipboard scientists (see
Appendix I) using standard techniques of visual examination, smear slide
and carbonate bomb analyses (DSDP, Vol. 18).
Sediments were then clas-
sified according to the classification system used on each leg of the
Deep Sea Drilling Project.
These classifications are all based on the
percentage of major components; however, the cutoff precentage for each
of the lithologies varied from leg to leg.
For this study, the classi-
fication has been standardized as follows:
>30% biogenic, detrial and volcanic Si02
1)
siliceous sediments:
2)
calcareous-siliceous sediments:
3)
calcareous sediments:
4)
black shales:
20-30% S102, 30-70% CaCO3
>30% CaCO3
black color, >30% terrigenous components,
variable CaCO.. and SiO
content
2
Age
The ages of the sediments were determined by the shipboard scientists (see Appendix I).
Foraminiferal, nanno fossil, radiolarian and
diatom species assemblages were determined for selected horizons.
The
species assemblages were then compared to standard biostratigraphic
charts in order to determine the geologic age.
Sedimentation Rate
In most cases, sedimentation rates were determined by shipboard
scientists and the individual authors of the Initial Reports of the Deep
Sea Drilling Project (see Appendix I).
The paleontological age of dated
horizons was plotted against the depth of the horizon in order to generate a sedimentation rate curve for the cored interval.
in the curves represent uniform rates of sedimentation.
Linear segments
The actual
sedimentation rate was then computed by measuring the thickness of the
sediment interval between the two paleontologically dated horizons at
the top and bottom of the linear segment.
Where these curves were not
available, sedimentation rates were determined directly from the paleontological data available for selected intervals in the cored sediment.
Total Organic Carbon
The total organic carbon by weight percent (TOG) is based on DSDP
Samples are first acidi-
burn technique analyses of selected samples.
fied to remove any
GaGO3.
The residual organic carbon is then converted
to CO2 at temperatures in excess of 1600°C.
A Leco carbon analyzer
measures the thermal conductivity of the gas mixture which in turn
reflects the percentage of CO2 or organic carbon in the sample with an
analytical error of ±0.04% TOG (DSDP, Vol. 9).
Sedimentation rate
intervals that had the largest number of TOG analyses were selected for
this study.
The TOG analyses were then averaged over each distinct
lithology within a sedimentation rate interval.
In this way it was
7
possible to generate a uniform sedimentation rate and an average TOC
value for each sediment interval that represented a distinct lithology.
Accumulation Rates
Porosity and bulk density estimates were used to calculate grain
accumulation rates according to the method of Van Andel et al.
(1975) as
shown below:
Grain Accumulation Rate
=
l00(sedimentation rate) (wet bulk density
-.01025 porosity)
Organic carbon accumulation rates were calculated after the method of
Van Andel et al. (1975) as shown below:
Organic Carbon Accumulation Rate = (total organic carbon) (grain accumulation rate)
The porosity, density, sedimentation rate and TOC values used in the
calculations represent the average value for each sediment interval with
a distinct lithology.
The porosity and density estimates are based on
DSDP Gamma Ray Attenuation Porosity Evaluator (GRAPE) analyses and have
an analytical error of 5% and +0.05 g/cm3, respectively (DSDP, Vol. 9).
Van Andel et al. (1975) indicate that the error in accumulation rate
estimates is greater than for sedimentation rate estimates and is in the
order of 10% of the calculated value.
Graphical and Statistical Analysis
All of the graphs were prepared on log-log plots after the method
employed by MUller and Suess (1979) in order to facilitate comparison
with data for recent sediments.
Sedimentation rate was plotted against
total organic carbon and the graph was analyzed for groupings of data on
the basis of age, lithology or environniental setting.
Organic carbon
was plotted against grain accumulation rate to eliminate the effect of
variable porosity in sedimentation rate estimates that arises from
differential compaction.
Organic carbon accumulation rates were plotted
against grain accumulation rates after the method and justification
given by MUller and Suess (1979).
Trends on each of the graphs were
defined, and the log values were subjected to linear regression analysis
to develop mathematical expressions and correlation coefficients for the
observed relationships.
Regression equations for each of the graphs
were then replotted on log-log plots in order to clarify the presentation of results.
Linear regression analysis of the graphs was conducted using the
computerized Statistical Package for the Social Sciences (SPSS, Nie et
al., 1974).
Log values were used in order to develop linear mathemati-
cal expressions following the standard practice for linear regression
analysis of non-linear curves (Neter and Wasserman, 1974).
The derived
linear expression (LogY = b logx + a) actually represents the power
ab
relation (y = 10 x ).
.
Pearson's correlation coefficient, R, measures
the degree to which the linear expression fits the data and, when R is
squared, the degree of explained variance (Nie et al. ,
1975).
To sim-
plify the presentation of results, only the linear expression of the
power relations and the R value have been given.
RESULTS AND DISCUSSION
Figure 2 depicts the general relationship between sedimentation
rate and organic carbon content in ancient marine sediments.
In general,
the organic carbon content increases and then decreases with increasing
sedimentation rate.
This trend in poorly defined, however, and there is
a large scatter in the total organic carbon values at moderate rates of
sedimentation ("40-SO rn/my).
Effect of Environmental Setting and Geologic Age
Figure 2 also shows the environmental setting and age of each data
point.
High organic carbon contents and moderate sedimentation rates
tend to represent Cretaceous sedimentation of passive rift margins;
moderate organic carbon contents and high rates of sedimentation tend to
represent Pleistocene sedimentation on active continental margins; while
low organic carbon contents and low sedimentation rates tend to reflect
sedimentation on deep sea oceanic plates.
Each of these groups or
"clusters" of data contain numerous exceptions and indicate that geolog-
ic age and environmental setting have only a general control on the
relationship between organic carbon and sedimentation rate.
Effect of Litho logy
Figure 3 shows that significant zones or fields of data do occur on
the basis of lithology.
Four lithologic fields can be identified from
Figure 3 as follows:
a)
Calcareous field:
The calcareous field includes chalk, limestone,
mans, nanno oozes and calcareous or nannofossil rich clays.
Total
organic carbon varies from 0.1 to 0.17% by weight while sedimentation rate varies from 4.5 to 41.5 rn/my.
The sediments range in age
from Cretaceous to Pleistocene and represent deposition on active
margins, passive margins and in deep ocean basin environments.
b)
Calcareous-siliceous field:
The calcareous-siliceous field is
largely composed of radiolarian rich nanno ooze with subordinate
10
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Figure 2.
CRETACEOUS
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Organic Carbon Versus Sedimentation Rate Showing
Environment of Deposition and Geologic Age.
TOC
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Organic Carbon Versus Sedimeìtation Rate Showing
Lithologic Field Zonation.
12
data from cherty limestone.
The total organic carbon by weight
percent increases from 0.12 to 0.26% while the sedimentation rate
varies from 3.4 to 20 rn/my.
The sediments typically represent deep
ocean sedimentation of Oligocene to Pliocene age.
c)
Siliceous field:
The siliceous field includes silty clays (detrial
silica), diatomites (biogenic silica), silty siliceous clays (bio-
genic, volcanic and detrial silica) and volcanic rich radiolarian
nanno oozes.
Total organic carbon varies from 0.19 to 1.97 percent
by weight while the sedimentation rate varies from 2.3 to 174 m/my.
Sediment intervals represent inland sea, marginal back arc basin,
active and passive continental margin, and deep ocean basin environments of deposition that range in age from Jurassic to Pleistocene.
d)
Black shale field:
The black shale field includes interbedded
black clays and limestone, black mans, sapropels and black silty
clays.
Total organic carbon by weight percent ranges from 0.4 to
5.4% while sedimentation rate varies from 4.0 to 230 rn/my.
The
sediment intervals are generally Cretaceous but range from Jurassic
to the Pleistocene in age.
The geologic setting includes inland
sea and passive continental margin sedimentation.
The majority of
Cretaceous data represents the early opening of the Atlantic Ocean.
Lithologic Effect on Total Organic Carbon Content
Figure 3 indicates that a definite relationship exists between
lithology and total organic carbon content.
In general, for any given
sedimentation rate, the organic carbon content increases from calcareous
sediments to calcarous siliceous sediments to siliceous sediments to
13
black shales.
Furthermore, there is a definite separation of data
between each of the lithologic fields with the exception of an overlap
between the black shale and siliceous field.
The lithologic effect on organic carbon content is related to the
degree of aeration of the sediment which effects the aerobic microbial
degradation of organic matter (Coleman et al., 1979).
Black shales
represent oxygen deficient or anoxic environments of deposition.
More
organic matter is preserved because the aerobic stage of microbial
degradation has been foreshortened or bypassed.
Similarly, siliceous
sediments are less permeable, and therefore less aerated than calcareous
sediments.
Krumbein and Sloss (1963) indicate that the lower permeabil-
ity of siliceous sediments is due to the lower solubility of Si02 (as
compared to CaCO3) in near surface sediments, and the lower percentage
of clay sized particles (i.e. siliceous sediments contain silt sized
quartz and diatoms whereas calcareous sediments contain clay sized
nannofossils).
The partial overlap between the black shale and siliceous fields in
Figure 3 suggests that the siliceous sediments within the overlap region
were deposited under oxygen deficient conditions more typical of black
shale formation.
This oxygen deficient condition could occur in silled
basins, or in open marine conditions where the 02 minimum in the oceans
intercepts the continental margin.
Siliceous sediments deposited under
these conditions would have a smilar total organic carbon content and
therefore a similar source rock potential as black shales.
Under less aerated conditions, aerobic microbial degradation is
reduced.
The organic matter is less degraded and the production of
nearsurface diagenetic cements is reduced (Coleman et al., 1979).
This
14
explains why the oil generation and oil migration potential also increases from calcareous to siliceous to black shale sediments along with
total organic carbon content.
Lithologic Effect on the Relationship Between Sedimentation Rate and
Total Organic Carbon Content
The lithologic effect clarifies the relationship between sedimentation rate and organic carbon content shown in Figure 2.
The data in
Figure 2 can be broken down into lithologic fields as shown in Figure 3.
Each of these lithologic fields depicts a unique relationship between
For each lithology, the
organic carbon content and sedimentation rate.
organic carbon content first increases, and then decreases with increasing sedimentation rate.
Low Rate of Sedimentation:
Increasing Organic Carbon Content
Figure 3 shows that the trend of increasing organic carbon with
sedimentation rate is present for each lithology and is the dominant
trend at low rates of sedimentation (less than 14 rn/my).
The trend in
each field was subjected to linear regression analysis using log values
(see Procedure, Graphical and Statistical Analysis).
The relationships
are depicted in Figure 4 and expressed in Table 1 under Relationship A.
Figure 4 shows that the slope of Relationship A increases from
calcareous to siliceous to black shale sediments.
The increasing slopes
indicate the relative effectiveness of sedimentation rate in preserving
the organic carbon in each of these lithologies.
In Table 1, Pearson's
coefficient of correlation, R, varies from moderate (.52) in black
shales to good (.88) in siliceous sediments.
The poorer correlation in
15
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10
SEDIMENTATION
Figure 4.
I
I
I
21.13
2.50
I
I
14.10
I
2.00
1.50
40.80
RATE (SR)
tOO
M/M.Y.
Organic Carbon Versus Sedimentation Rate.
Low rates of
sedimentation are characterized by increasing organic
carbon content.
High rates of sedimentation are
characterized by decreasing organic carbon content.
Trend A in siliceous sediments reflects the anomalous
case of increasing organic content at high rates of
sedimentation.
TABLE 1.
ORGANIC CARBON VS SEDIMENTATION RATE
MATHEMATICAL EXPRESSION AND STATISTICAL CORRELATION FOR EACH LIThOLOGY
LITHOLOGY
RELATIONSHIP A
INCR TOC WITH SED RATE
BLACK SHALE
LOG(TOC)=.64L0G(SR)- .55
R
.52
RELATIONSHIP B
DECR TOC WITh SED RATE
LOG(TOC)=-. 73LOG(SR)+1.72
R
.91
CRITICAL
SED RATE
40.8
LOG= 1.66
SILICEOUS
LOG(TOC)=.S1LOG(SR)-.80
.88
LOG(TOC)=-.34L0G(SR).30
.45
21.1
LOG=1.325
(SILTYCLAY,
DIATOM ITE)
CALCAREOUS
SILICEOUS
LOG(TOC)=.37LOG(SR)-1. 10
.75
CALCAREOUS
LOG(TOC)=.16LOG(SR)-1.07
.67
LOG(TOC)=-.35L0G(SR)..48
.88
14.0
LOG= 1.15
R
PEARSON'S COEFFICIENT OF CORRELATION, (0.0 - 1.0)
TOC = TOTAL ORGANIC CARBON, (WT, %)
SR = SEDIMENTATION RATE, (M/MY)
C'
17
the black shale field reflects varying degrees of anoxicity (oxygen
deficiency) at the time of deposition, and the highly variable CaCO3
contents typical of black shale sediments.
In the calcareous field, the
moderate R value (.67) is due to variable CaCO3-clay contents.
As
stated above, the anoxicity of bottom waters and the amount of highly
soluble CaCO3 effect the aeration of the sediment and the degree of
aerobic microbial degration of organic matter.
The trend of increasing organic carbon content with sedimentation
rate reflects the important effect of microbial degradation (Coleman et
al., 1979).
As sedimentation rate increases, the zone of aeration
becomes smaller and the sediment makes a more rapid passage through the
zone as the burial rate increases.
Aerobic microbial degradation be-
comes increasingly less efficient and more organic carbon is preserved
(Figure 5).
Since aerobic microbial degradation is a near surface
event, it would be expected to have a similar effect on organic preservation in recent sediments.
In Figure 6, MUller and Suess (1979) have
shown that the same trend of increasing organic carbon with sedimentation rate is also present in recent sediments.
Coleman et al. (1979) also indicate that the organic matter preserved will have a better potential to generate and migrate oil because
reduced microbial activity minimizes the degradation of organic matter
and decreases the production of diagenic cements (Figure 5).
It should
be noted however, that a minimum organic content (TOC) is required
before any oil migration will occur (.5% TOC clastics, .3% TOC carbonates; Tissot, 1978).
To summarize, as sedimentation rate increases, the total organic
carbon by weight percent increases, the quality of the organic matter
18
[ Prospect
Aerobic zone
Sulfate
red u c t ion
Fermentation
j
zone
Thermal
maturation
Very slow sedimentation
All organics destroyed
Zero
Slow sedimentation Massive
modification sulfides, carbonates
Poor
zones
Intermediate rates Significant
modification of organic matter:
Liquid
hydrocarbon
'window'
carbonates
F
Fairly rapid sedimentation
Organic
matter little affected by aerobic and
sulfate reduction zone processes
Very rapid sedimentajion
Liquid Pydrocarbons may
be destroyed
Figure 5.
Fair
Good
Uncertain
Effect of Sedimentation Rate on the Degraaation of Organic.
Matter (after Coleman et al., 1979).
19
>-
300
>->---
<OlE
200
100
0
I
z
10
8
W Baltic
0
00)
Peru
A
I
* Oregon
0 NW Africa
0 0
0
0
A Argentine Basin
Central Pacific
0.1
10
SEDIMENTATION
Figure 6.
100
RATE
1,000
10,000
(m/M.Y.)
Organic Carbon Versus Sedimentation Rate in Recent
Sediments (modified after MUller and Suess, 1979).
20
preserved increases, and the oil generation and oil migration potential
of the sediment may increase.
High Rate of Sedimentation:
Decreasing Organic Carbon Content
The lithologic fields in Figure 3 show a reverse trend of decreas-
ing organic carbon content at high rates of sedimentation (greater than
41 rn/my).
These reverse trends were subjected to linear regression
analysis in each of the lithologic fields.
The relationships are de-
picted in Figure 4 and expressed in Table 1 under Relationship B.
The
critical sedimentation rate for each lithology is the point at which the
organic carbon content starts to decrease and Relationship B begins.
Figure 4 and Table 1 show that this critical sedimentation rate varies
from 14 rn/my in calcareous sediments to 21 rn/my in siliceous sediments
to 41 rn/my in black shales.
Pearson's coefficient of correlation (R)
ranges from moderate (.45) for siliceous sediments to excellent (.91)
for black shales (Table 1).
There are two exceptions to the reverse trend of decreasing organic
carbon:
1) the reverse trend was not observed for calcareous-siliceous
sediments, and 2) the siliceous field shows an additional trend of
increasing organic carbon content (Trend A, Figures 3 and 4).
The first
exception is due to the absence of data for calcareous-siliceous sediments at high rates of sedimentation.
The second exception represents a
continuation of the trend of increasing organic carbon observed at low
rates sedimentation.
The reverse trend of decreasing organic carbon in each lithologic
field (Relationship B), the lower R value for siliceous sediments, and
the anomalous secondary Trend A of increasing organic carbon in silice-
21
ous sediments are all related to a clastic dilution effect.
Clastic
dilution occurs at high rates of sedimentation when the input of organic
matter from primary productivity does not keep pace with the input of
clastic sediments.
When this occurs, the organic carbon content de-
creases with increasing sedimentation rate (Relationship B, Figure 4).
The lower R value for the siliceous sediments reflects the various
degrees of clastic dilution which may occur.
The anomalous secondary
Trend A of increasing organic content in siliceous sediments (Figure 4)
represents the rare case when no clastic dilution occurs at high rates
of sedimentation.
The clastic dilution effect is supported by the data of MUller and
Suess (1979) for recent hemipelagic sediments.
In Figure 7, their data
show two distinct trends at high rates of sedimentation.
Where high
sedimentation rates are associated with high primary biological produc-
tivity, the organic carbon content continues to increase with increasing
sedimentation rate (Data Group A2).
However, where high sedimentation
rates are associated with a low primary productivity region, and clastic
dilution occurs, organic carbon content decreases with sedimentation
rate (Data Group B).
This clastic dilution effect does not occur at low
rates of sedimentation (Data Group Al).
For the ancient siliceous sediments of Figures 3 and 4, the clastic
dilution effect at high rates of sedimentation is dominated by data
representing Pleistocene sedimentation of active continental margins.
The case of no clastic dilution (Trend A), represents data from regions
which are presently highly productive (i.e. Black Sea, Red Sea).
Trend
A was not observed for black shale or calcareous sediments (Figure 4).
In the case of black shales this may be due to the fact that primary
22
300>-
I->2O0-
'
I
cJE
,-
3-"Ti,''
0
100-
0-__ 'B
A
=
z
o
I0
=
-
/
/
o
_u_.
L
-/
o
0.1-
-,
4.
!IIIJlI
I
10
LOW RATES
T
I
111111
100
1,000
10,000
HIGH RATES
SEDIMENTATION
Figure 7.
'8
RATE
(m/M.Y.)
Relationship Between Sedimentation Rate, Organic Carbon
Content and Primary Productivity for Recent Marine
Sediments (modified after MUller and Suess, 1979)
A1:
At low rates of sedimentation, organic carbon
content increases even though primary productivity
is low and constant relative to increasing clastic
input (i.e. increasing sedimentation rate).
A2:
At high rates of sedimentation, organic carbon
content increases when primary productivity remains
high relative to increasing clastic input.
B2:
At high rates of sedimentation, organic carbon
content decreases when primary productivity is low
and constant relative to increasing clastic input.
productivity was never high enough to offset the effect of clastic
dilution.
In the case of calcareous sediments, it may be that the
higher primary productivity required to offset clastic dilution was
characterized by siliceous phytoplanktcn, similar to the higher productivity regions in modern oceans.
In this case, siliceous phytoplankton
(diatoms) would dominate over calcareous nanno plankton and siliceous,
rather than calcareous sediments would be deposited.
This effect would
also explain the smaller range of clastic dilution (higher R value) in
calcareous and black shale sediments as compared to siliceous sediments
(Table 1, Relationship B).
The clastic dilution effect only occurs at high rates of sedimentation and effects only the organic matter preserved by weight percent.
The quality of organic matter preserved should continue to increase as
sedimentation rate increases since microbial degradation is increasingly
inefficient.
Therefore, the oil generation and oil migration potential
of the sediment may also continue to increase with sedimentation rate
even though the total organic carbon content by weight percent decreases.
Effect of Differential Compaction
The sedimentation rates of Figure 3 reflect various stages of
porosity reduction associated with differential compaction.
In Figure 8
the effect of differential compaction has been eliminated by converting
the sedimentation rates of Figure 3 into grain accumulation rates which
removes the effect of variable porosity (see Methods, Accumulation
Rate).
In Figure 8, as in Figure 3, the same four lithologic fields are
identified and each of the lithologic fields shows the same trends of
24
TOC
LOG10 TOC
1.50
I.-.
10
.90
0
0
I-
.30
< 1.0
C-)
-.30
z
cr
o
_j
-.90
0.IBLACK SHALE
0
I
F7
kJ
-1.50
CALCAREOUS-SILICEOUS
SILICEOUS
(SILTY CLAY-DIATOMITE)
BLACK SHALE - SILICEOUS
OERLAP RçGION
I
LOG10GAR
GR
.75
2.35
00
GRAIN
Figure 8.
I
2.95
1,000
ACCUMULATION
CALCAREOUS
I
3.55
4.15
4.75
0,000
RATE (GAR) q/cm2/M.Y.
Organic Carbon Versus Grain Accumulation Pate Showing
Lithologic Fields in the Absence of Differential Compaction
Effects.
TOC
LOG10 TOC
1.50
10.0.90
C-)
0
I-
z
o
'Z
C-)
.30
10-
< 01I-
0
I-
o(,g.
I
- .50
LOG,0 GAR
I
I
2.35
1.75
I
ii
II
G AR
100
ii
2.95
3.55
I
775 1,000 1622
GRAIN ACCUMULATION RATE
Figure 9.
4.15
I
5370
(GAR)
4.75
I
10,000
g/cm2/M.Y.
Organic Carbon Versus Grain Accumulation Rate.
Low rates
of grain accumulation are characterized by increasing
organic carbon content. High rates of grain accumulation
are characterized by decreasing organic carbon content.
ORGANIC CARBON VS GRAIN ACCUMULATION RATE
TABLE 2.
MATHEMATICAL EXPRESSION AND STATISTICAL CORRELATION FOR EACH LITHOLOGY
LITHOLOGY
RELATIONSHIP A
INCR TOC WITH GAR
R
RELATIONSHIP B
DECR TOC WITh GAR
R
CRITICAL
GAR
BLACK SHALE
LOG(TOC)=.41LOG(GAR)-1.18
.52
LOG(TOC)=-.55LOG(GAR)+2.48
.91
5370
LOG=3.73
SILICEOUS
(SILTYCLAY, DIATOMITE)
LOG(TOC)=. 38LOG(GAR)-1. 35
.84
LOG(TOC)=-. 18LOG(GAR)+.30
.38
778
CALCAREOUS
SILICEOUS
LOG(TOC)=.42L0G(GAR)-1.93
.88
CALCAREOUS
LOG(TOC)=.14LOG(GAR)-1.34
.70
LOG=2.89
LOG(TOC)=-.44L0G(GAR)+.55
.94
1622
LOG=3. 21
R = PEARSON'S COEFFICIENT OF CORRELATION, (0.0 to 1.0)
TOC = TOTAL ORGANIC CARBON, (WT,
2
TOCAR = TOTAL ORGANIC CARBON ACCUMULATION RATE, (g/cm /MY)
GAR = GRAIN ACCUMULATION RATE, (g/cm2/MY)
IN)
0\
27
increasing, then decreasing organic carbon content with increasing
accumulation rate.
The trends in Figure 8 were subjected to linear
regression analysis and the results are depicted in Figure 9 and expressed in Table 2.
A comparison of Figure 4 and 9 and Tables 1 and 2, indicates that
differential compaction effects only the critical rate.
In Figure 4,
the critical sedimentation rate increases from calcareous sediments (14
rn/my) to siliceous sediments (21 rn/my) whereas the critical accumulation
2
rate in Figure 9 increases from siliceous sediments (780 g/cm /my) to
calcareous sediments (1620 g/cm2/my).
This reversal in critical rate
occurs because grain accumulation rates incorporate the grain density of
the sediment and CaCO3 has a higher grain density than Si02 (2.71 g/cm3
vs. 2.65 g/cm3; Gardner, 1974).
There is no significant change in the
statistical correlation (R) of the observed relationships (Tables 1 and
2)
Relationship Between Organic Carbon Content Versus Grain
Accumulation Rate and Organic Carbon Accumulation Rate Versus
Grain Accumulation Rate
The organic carbon content is the total organic carbon in the
sediment by weight percent.
The organic carbon accumulation rate is the
rate at which organic carbon is incorporated and preserved in the sediment.
Organic carbon accumulation rate has been plotted against grain
accumulation rate in Figure 10.
The same four lithologic fields identi-
fied in Figure 8 were also identified in Figure 10 and the trends in
each field were subjected to linear regression analysis (Figure 11,
Table 4).
28
TOCAR
LOG10 TOCAR
100,000 -
00 F
>:
4.20
N
10,000
o
3AO
1,000 -
2
4
2.60
BLACK SHALE
SILICEOUS
100(_)
ISILTY CLAY-DIATOMITE)
BLACK SHALE SILICEOUS
1.80
0
4
OVERLAP REGION
ECALCAREOUS - SILICEOUS
10 -
CALCAREOUS
1.00 ft_
2.40
LOG10GAR 1.60
3.20
4.00
I
GAP
00
1,000
0,000
5.60
4.80
I
100,000
GRAIN ACCUMULATON RATE (GAR) g/cm2/M.Y.
Figure 10.
Organic Carbon Accumulation Rate Versus Grain Accumulation
Rate Showing the Contraction of Lithologic Fields.
29
TOCAR
LOG10 (TOCAR)
100,000 5.0
>.;
c.J
E
o
C
4.
10,000
o g
OLii
i.-.
1,000
oz0
Ix
_j
2.1
001.1
0
C-)
10 1.0
L0G10(GAR)
1.6
I
GAR
100
GRAIN
Figure 11.
II
778 000 1622
I
I
5370 0,000
ACCUMULATION RATE (GAR)
I
00,000
g/cm2/M.Y.
Organic Carbon Accumulation Rate Versus Grain Accumulation
Rate.
Low rates of grain accumulation are characterized
by increasing rate of organic carbon accumulation.
High
rates of grain accumulation are characterized by a slower
increase in the rate of organic carbon accumulation.
ORGANIC CARBON ACCUMULATION RATE VS GRAIN ACCUMULATION RATE
TABLE 3.
MATHEMATICAL EXPRESSION AND STATISTICAL CORRELATION FOR EACH LITHOLOGY
LITHOLOGY
RELATIONSHIP A
INCR TOCAR WITH CAR
R
RELATIONSHIP B
INCR TOCAR WITH GAR
R
LOG(TOCAR)=1.42L0G(GAR)-1.18
.90
LOG(TOCAR)=.45L0G(GAR)+2.48
.88
SILICEOUS
LOG(TOCAR)=1.35L0G(GAR)-1.30
(SILTYCLAY, DIATOMITE)
.98
LOG(TOCAR)=.82L0G(GAR)+.30
.88
CALCAREOUS
SILICEOUS
LOG (TOCAR)=1. 41LOG(GAR)-1.91
.99
CALCAREOUS
LOG(TOCAR)=1.14LOG(GAR)-1.33
.99
BLACK SHALE
R = PEARSONS COEFFICIENT OF CORRELATION, (0.0 to 1.0)
TOC = TOTAL ORGANIC CARBON, (WT, %)
TOCAR = TOTAL ORGANIC CARBON ACCUMULATION RATE, (g/cm2/MY)
CAR = GRAIN ACCUMULATION RATE, (g/cm2/MY)
CRITICAL
GAR
5370
LOG=3.73
778
LOG=2.89
LOG(TOCAR)=.56L0G(GAR)+.54
.96
3.21
31
A comparison of these figures indicates that the organic carbon
content and organic carbon accumulation rate both increase up to a
critical grain accumulation rate (Relationship A, Figure 8 and 9 vs.
Relationship A, Figures 10 and 11).
In both cases, the critical accumu-
lation rate ranges from 780 g/cm2/my for siliceous sediments to 1620
2
g/cm /my for calca reous sediments to 5370 g/cm2/my for black shales
(Figure 9, Table 3 and Figure 11, Table 4).
At high rates of grain accumulation, above the critical rate,
organic carbon content decreases with increasing grain accumulation rate
(negative slope of Relationship B, Figure 10).
The organic carbon
accumulation rate, however, continues to increase with grain accumulation rate, but at a slower rate (i.e. flatter, positive slope of Relationship B, Figure 11).
The decrease in organic carbon content and the
flatter slope for organic carbon accumulation rate both reflect the
effect of clastic dilution.
The organic carbon accumulation rate in-
creases, however, instead of decreasing, because the organic carbon that
is incorporated into the sediment is preserved at a faster rate due to
reduced aerobic microbial degradation at higher rates of grain accumulation.
The relationship between organic carbon content and organic
carbon accumulation rate thus supports both the effect of clastic dilution and the effect of reduced aerobic microbial degradation at higher
rates of grain accumulation.
Lithologic Effect on Organic Carbon Accumulation Rate
A comparison of Figures 8 and 10 shows that the influence of lithology is reduced when organic carbon accumulation rates are used instead
of organic carbon content.
The lithologic fields in Figure 10 are still
32
well defined, but they are narrower and the statistical correlation (R)
of the trends in each field increases markedly (Table 3, R value .88-.99
vs. Table 2, R value .38-.94).
All the data from Figure 10 was subjected to linear regression
analysis, irregardless of lithology.
Figure 12 shows that the statisti-
cal correlation (R) remains high (.89).
The high statistical correla-
tion indicates that the organic carbon accumulation rate could be deter-
mined from grain accumulation rate even when the lithology is not known.
Since total organic carbon content equals the total organic carbon
accumulation rate divided by grain accumulation rate, the source rock
potential of a sediment could be determined without knowing the lithology if the grain accumulation rate is known.
IMPLICATIONS OF PETROLEUM EXPLORATION
The results of this study indicate that sedimentation rate and
grain accumulation rate could be used to determine the source rock
potential of marine sedimentary basins.
In frontier regions, sedimenta-
tion rate and grain accumulation rate can be determined directly from
seismic reflection records.
Vail et al. (1977) has shown that seismic traces represent chronostratigraphic horizons.
When these horizons are dated from outcrop or
well data, sedimentation rates can be calculated by measuring the thickness of sediment between two key chronostratigraphic horizons.
In a
similar fashion, sedimentation rate maps can be produced from seismic
isopach maps.
The lithology of the interval can be determined from well
data after drilling, or predicted from outcrop and seismic character
analysis prior to drilling (Vail et al., 1977).
When the lithology is
33
LOG10 TOCAR
TOCAR
100,000 - 5.00
F-
4.20
10,000
:
4
ou
z
..
en
3.40
1,0002.60
-J
O
00-
S.
1.80
/
0- l.O0
LOG 0GAR
GAR
3.20
2.40
1.60
4.00
I
I
I
too
I,OOO
10,000
GRAIN
Figure 12.
ALL
LITHOLOGIES
LOG (TOCAR)I.3OLOG(GAR)-l.37, R.89
ACCUMULATION
4.80
5.60
100,000
RATE (GAR) g/cm2/M.Y.
Organic Carbon Accumulation Rate Versus Grain Accumulation
Rate Without Lithologic Field Zonation.
34
known to be calcareous, siliceous or black shale, sedimentation rate
maps can be converted into maps of total organic carbon by using the
appropriate lithologic field or curve.
The total organic carbon cutoff
for petroleum source rocks (0.5 TOC clastics, 0.3% TOG carbonates;
Tissot, 1977) would then be used to define the volume of the source rock
facies.
The grain accumulation rates can also be determined from seismic
reflection records since grain accumulation rate (GAR) is calculated
from sedimentation rate (SR) and grain density (g){GAR = lOO(SR)(g);
Van Andel, l975}.
The sedimentation rate can be determined from seismic
records as outlined above.
Grain density can be determined from seismic
velocity or from time interval maps.
The relationship between velocity and grain density is shown in
Figure 13.
This empirical relation is based on the average grain densi-
ty and average sonic velocity of the DSDP sediment intervals used in
this study.
These sediment intervals range from 100 to 1000 meters in
subsurface depth and the relationship should be tested for accuracy at
subsurface depths greater than this.
The grain density determinations are based on DSDP Grape analysis
(DSDP, Vol. 9) and have an analytical error of +5% (Van Andel, 1975).
Sonic velocity estimates have an accuracy of +0.5% (DSDP, Vol. 19).
The
statistical correlation (R value) of the relation is given in Figure 13
as .97.
This high degree of correlation indicates that grain density
estimates from sonic velocity will be nearly identical to those from
Grape analysis and should not effect grain accumulation rate calculations.
The prospect of determining grain accumulation rates and sedimenta-
35
8.50
6.90
0
E
5.30
3.70
:''
'
3. CLEAN LIMESTONE
AT DEEPER DEPTHS
/
-
U.,
.
-
S
2. CLEAN SANDSTONE
AT DEEPER DEPTHS
,y
I. SHALES
100 TO 1,000 METERS,,,/I'
a
.50
..
I
0
.8
GRAIN
Figure 13.
I
I
1.6
2.4
DENSITY (pg)
I
I
3.2
I
4.0
g/cm3
Sonic Velocity Versus Grain Density
1.
Shales: include calcareous, calcareous-siliceous,
siliceous and black shale DSDP sediments used
in this study.
2.
Deep Clean Sandstone: equivalent to the values
for pure quartz crystals (Gardner, 1974).
3.
Deep Clean Limestone:
equivalent to the values
for oure calcite crystals (Gardner, 1974).
36
tion rates from seismic reflection records has important implications
for source rock evaluations in frontier regions with limited well control.
By using Figure 12, the total organic carbon content, or source
rock facies, of a marine sedimentary basin can be identified from seismic reflection analysis prior to exploration drilling.
Once the lithol-
ogy is determined from outcrop data, subsurface well data or seismic
character analysis, the total organic carbon content can be more accur-
ately predicted from either sedimentation rate, or grain accumulation
rate, by using the appropriate lithologic field or curve (Figures 3 and
4, Figures 8 and 9 or Figures 10 and 11).
The oil generation an oil migration potential of a marine sedimentary basin can also be estimated from sesimic records by determining the
amount of total organic carbon above the source rock cutoff (.5% TOC
clastics, .3% TOG carbonates), the magnitude of the accumulation rate
(relative degree of preservation), the volume of the source rock, and
its burial history (thermal maturation).
CONCLUSIONS
The results of this study are summarized as follows:
1.
A definite relationship exists between total organic carbon content
and sedimentation rate for fine grained ancient marine sediments of
Jurassic to Pleistocene age.
The relationship is strongly depen-
dent on lithology but is relatively uneffected by geologic age,
environmental setting or differential compaction (Figures 2, 3, 4,
8 and 9).
In general, for any given sedimentation rate, the organ-
ic content increases from calcareous to siliceous to black shale
sediments (Figures 3 and 4).
37
2.
For each of these lithologies, quantitative relationships exist
between total organic carbon content and sedimentation rate (Fig-
ures 3 and 4), and total organic carbon and grain accumulation rate
(Figures 8 and 9).
The organic carbon content first increases (due
to reduced aerobic microbial degradation) and then decreases (due
to clastic dilution) with increasing sedimentation or grain accumulation rate.
The quality of organic matter preserved, and the oil
generation and oil migration potential of petroleum source rocks
should continue to increase with sedimentation rate due to reduced
aerobic microbial degradation.
3.
Similar quantiative relationships also exist between total organic
carbon accumulation rate and grain accumulation rate and show a
higher degree of statistical correlation (Figures 10 and 11).
The
lithologic effect is less pronounced so that total organic carbon
content could be predicted from grain accumulation rates even when
the lithology is not known (Figure 12).
4.
Sedimentation rates and grain accumulation rates could be determined from seismic reflection records or from seismic iospach or
time interval maps (Figure 13).
By using the appropriate figure,
sedimentation or grain accumulation rate maps could be converted
into total organic carbon maps and the petroleum source rock facies
outlined.
These results indicate that sedimentation rate and grain accumulation rate could be used as criteria for source rock evaluation in marine
sedimentary basins of frontier regions.
Future work should be directed
toward testing the use of these criteria in an exploration situation.
The establishment of sedimentation rate and grain accumulation as cri-
38
teria for source rock evaluation would substantially reduce the risk of
frontier exploration, and would provide a mechanism for comparing the
petroleum potential of offshore exploration regions.
39
REFERENCES
Initial Reports of the
Barker, P. F., I. W. D. Dalziel, et al.
1976.
Deep Sea Drilling Project. U.S. Govt. Printing Office, Washington,
36:5-15, 207-257.
D.C.
Blatt, H., G. Middleton, and R. Murray.
1972.
Prentice Hall Inc., N.J.
Rocks.
634 pp.
Origin of Sedimentary
Initial Reports of the Deep
Bolli, H. M., W. B. F. Ryan, et al. 1978.
U.S. Govt. Printing Office, Washington, D.C.
Sea Drilling Project.
40:5-28, 29-182, 357-451.
Accumulation and transformation of organic
1964.
Bordovskiy, 0. K.
Accumulation of organic matter
substances in marine sediments.
3:
Marine
Geology.
3:33-82.
in bottom sediients.
Burial rate a key to
Coleman, M. L., D. C. Curtis, and H. Irwin.
1979.
source and reservoir potential. World Oil, March. p. 83-92.
1973.
Initial Reports of the Deep
Creager, J. S., D. W. Scholl, et al.
U.S. Govt. Printing Office, Washington, D.C.
Sea Drilling Project.
19:3-16, 19-9, 217-277, 325-369, 370-411, 463-553.
Anoxic environments and oil
1980.
Demaison, G. J., and G. T. Moore.
Organic Geochemistry.
2:9-31.
source bed genesis.
Submarine slumping and location of cal bodies.
1946.
Fairbridge, R. W.
AAPG Bull.
30:84-92.
1974.
Formation
Gardner, G. H. F., L. W. Gardner, and A. R. Gregory.
velocity and density - The diagnostic basics for stratigraphic
39(6):77O-780.
Geophysics.
traps.
1972.
Gross, M. G., A. G. Carey, Jr., G. A. Fowler, and L. D. Kuim.
Distribution of organic carbon in the surface sediment, northeast
Columbia River Estuary and Adjacent Ocean
Pacific Ocean.
In:
Bioenvironmental Studies, A. T. Pruter, and D. L. Alverson
Waters:
(eds.), University of Washington Press. p. 254-264.
Initial Reports of the Deep Sea Drilling
Hays, J. D., et al.
1972.
9:3-20A,
Project. U.S. Govt. Printing Office, Washington, D.C.
43-208, 209-316, 615-704.
1977.
Organic carbon in
Heath, G. R., T. C. Moore, and J. P. Dauphin.
The Fate of Fossil Fuel CO2 in the Oceans,
In:
deep sea sediments.
N. R. Anderson, and A. Malahoff (eds.), New York, Plenum Press.
p.
605-625.
Initial Reports of the
1972.
Hollister, C. 0., J. I. Ewing, et al.
U.S. Govt. Printing Office, Washington,
Deep Sea Drilling Project.
11:5-9, 219-312.
D.C.
Stratigraphy of the Lacustrine Sedimentation in the
1978.
HsU, K. J.
Initial Reports of the Deep Sea Drilling Project, D. A.
In:
Sea.
Ross, Y. P. Neprochnov, et al (eds.), Vol. 42, Part 2, U.S. Govt.
Printing Office, Washington, D.C. p. 509-524.
Initial Reports of the Deep
1975.
Karig, D. E., J. C. Kingle, et al.
U.S.
Govt.
Printing
Office, Washington, D.C.
Sea Drilling Project.
31:5-21, 351-402.
Initial Reports of the Deep
1974.
Kennett, J. P., R. E. Houtz, et al.
U.S. Govt. Printing Office, Washington, D.C.
Sea Drilling Project.
29:3-16, 317-364.
Initial Reports of the Deep
1973.
Kuim, L. D., R. Von Huene, et al.
U.S. Govt. Printing Office, Washington, D.C.
Sea Drilling Project.
18:5-13, 31-96, 169-212, 213-223, 244-286, 287-376.
Initial Reports of the Deep Sea
1977.
Lancelot, Y., E. Seibold, et al.
U.S.
Govt.
Printing
Office, Washington, D.C.
Drilling Project.
41:7-18, 21-161, 163-232, 421-491.
Productivity, sedimentation rate
1979.
MUller, P. S., and E. Suess.
Deep-Sea
and sedimentary organic carbon content in the oceans.
26: 1347-1362.
Research.
Applied Linear Statistical Models.
1974.
Neter, J., and W. Wasserman.
Richard D. Irwin, Inc. 842 pp.
Statistical Package for the Social
1975.
SPSS:
Nie, N. H., et al.
McGraw-Hill, Inc. 675 pp.
Sciences.
Organic carbon and nitrogen distribution in
Romankevich, E. A.
1968.
8:825-838.
Okeanologia.
sediments of the Pacific Ocean.
Initial Reports of the
Ross, D. A., Y. P. Neprochmov, et al. 1978.
Deep Sea Drilling Project. U.S. Govt. Printing Office, Washington,
43(2):3-l5, 17-26, 293-355.
D.C.
Initial Reports of the Deep
Ryan, W. B. F., K. J. HsU, et al. 1973.
U.S.
Govt.
Printing
Office, Washington, D.C.
Sea Drilling Project.
13:5-17, 355-382.
Geologic Synthesis of Leg 19
1973.
Scholl, D. W., J. S. Creager.
(DSDP) Results; Far North Pacific, and Aleutian Ridge, and Bering
Initial Reports of the Deep Sea Drilling Project, J. S.
In:
Sea.
Creager, D. W. Scholl, et al (eds.), Vol. 19, U.S. Govt. Printing
Office, Washington, D.C. p. 897-913.
Cenozoic Diatoms from the Northeast Pacific, Leg
1973.
Initial Reports of the Deep Sea Drilling Project, L. D.
Kuim, R. Von Huene, et al (eds.), Vol. 18, U.S. Govt. Printing
Office, Washington, D.C. p. 673-797.
Schrader, H. J.
18.
In:
41
Norwegian Sea Cenozoic Diatom
1976.
Schrader, H. J., and J. Fenner.
Initial Reports of the Deep Sea Drilling
In:
Biostratigraphy.
Project, M. Talwani, G. Udintsev, et al (eds.), Vol. 38, U.S. Govt.
Printing Office, Washington, D.C. P. 921-1100.
Mineral phases formed in anoxic sediments by microbial
Suess, E.
1978.
decomposition of organic matter. Geochem. Cosmochim. Acta.
43:339-352.
Stratigraphy
1978.
Stoffers, P., Degens, E. T., and Trimonis, E. S.
and suggested ages of Black Sea sediments cored during Leg 42B.
Initial Reports of the Deep Sea Drilling Project, D. A. Ross,
In:
Y. P. Neprochnov, et al (eds.), Vol. 42, Part 2, U.S. Govt. Printing Office, Washington, D.C. p. 483-488.
Initial Reports of the Deep Sea
1976.
Taiwani, H., G. Udintsev, et al.
U.S. Govt. Printing Office, Washington, D.C.
Drilling Project.
38:3-19, 23-116, 151-387, 389-449, 451-519, 595-654.
Petroleum Formation and Occur1978.
Tissot, B. P., and D. H. Welte.
New York, Springer
rence, New Approach to Oil and Gas Exploration.
Verlag.
539 pp.
Deposition of organic matter in recent sediments.
Problems of Petroleum Geology, A Symposium, E. W. Wrather, F.
In:
H. Lahel (eds.), Syndey Powers Memorial Volume, AAPG.
p. 27-67.
Trask, P.
D.
1934.
Initial Reports of the Deep Sea
1971.
Tracey, J. I., Jr., et al.
Drilling Project. U.S. Govt. Printing Office, Washington, D.C.
8:5-16, 17-41, 61-134, 135-283.
Initial Reports of the Deep
1979.
Tucholke, B. E., P. R. Vogt, et al.
U.S. Govt. Printing Office, Washington, D.C.
Sea Drilling Project.
43:5-27, 195-321, 323-391.
Chrono1977.
Part 5.
Vail, P. R., R. G. Todd, and J. B. Sangree.
Seismic
In:
stratigraphic Significance of Seismic Reflections.
Stratigraphy - Applications to Hydrocarbon Exploration, C. E.
Payton (ed.), AAPG Memoir 26. p. 99-116.
Cenozoic
1975.
Van Andel, T. H., G. R. Heath, and 1. C. Moore, Jr.
History and Paleoceanography of the Central Equatorial Pacific
Ocean. GSA Memoir 143.
134 pp.
In:
Tectonic Summary of Leg 18.
1973.
Von Huene, R., and L. D. Kuim.
Initial Reports of the Deep Sea Drilling Project, L. D. Kuim, R.
Von Huene, et al (eds.), Vol. 18, U.S. Govt. Printing Office,
Washington, D.C. p. 961-976.
1974.
Initial ReWhitmarsh, R. B., 0. E. Weser, D. A. Ross, et al.
U.S. Govt. Printing Office,
ports of the Deep Sea Drilling Project.
23:5-31, 601-676, 677-752.
Washington, D.C.
42
Initial Reports of the Deep Sea
Yeats, R. S., S. R. Hart, et al.
1976.
U.S. Govt. Printing Office, Washington, D.C.
Drilling Project.
34:3-15, 19-80, 81-109, 109-153.
APPENDIX
APPENDIX I.
S'JMMATION 0! DATA FOR 1)51W SEDIMENT INTERVAL.S
Grain
Sod.
Leg
lo1e
Interval
Lith*
(m)
8
8
8
8
8
9
9
9
9
9
9
9
9
9
9
9
9
9
9
9
11
11
13
13
18
18
18
18
18
18
18
18
18
18
19
19
19
19
69
69
70
70
70
77
77
77
77
77
77
77
77
77
78
78
78
84
84
84
105
lOS
130
130
173
173
173
173
175
175
176
177
178
178
13
183
183
186
0- 30
32-146
0- 26
26- 50
50-320
0- 25
25- 42
42- 82
82-161
161-235
235-280
280-325
325-425
425-471
20- 50
50-223
223-315
0- 80
80-130
130-195
291-392
421-559
15- 58
58-563
0-138
138-203
203-250
250-280
0-119
119-225
0- 40
0- 61
0-195
195-750
0-130
210-240
250-500
0-925
Rate
(rn/my)
1
2.7
7.0
2.4
3.4
16.0
10.0
20.0
20.0
18.0
16.0
10.0
10.0
11.0
11.0
15.5
15.5
15.5
45.0
37.5
1
313.0
4
4
5.0
10.0
70.0
40.0
42.0
10.0
10.0
10.0
174.0
174.0
44.0
30.0
160.0
45.0
45.0
4.0
12.0
120.0
1
2
1
2
2
2
2
2
2
2
2
3
3
3
2
2
3
1
4
4
1
1
1
1
1
1
1
1
1
1
1
1
1
1
-
Accum.
Age
TOC
(weight %)
.19
.15
.23
.12
.17
.15
.21
.24
.22
.22
.26
.16
.13
.12
.25
.26
.14
1.16
.71
.29
1.28
.50
2.50
.61
.75
.65
.61
.56
.76
.56
.36
.29
.35
.37
.29
.60
1.47
.37
Range
Density
(g/cm3)
4-4
4-S
1-4
4-4
4-5
2-2
3-3
3-3
4-4
4-4
4-4
4-4
5-5
6-6
4-4
4-5
5-5
2-2
3-3
3-3
8-8
8-8
2-0
2-2
3-4
4-4
4-4
4-4
2-2
2-2
2-2
2-2
3-2
4_3
3-2
5-4
6-5
3-2
1.22
1.39
1.28
1.35
1.62
1.38
1.39
1.39
1.48
1.53
1.57
1.78
1.74
1.63
1.39
1.54
1.59
1.24
1.27
1.39
1.62
1.63
1.50
1.61
1.53
1.37
1.39
1.37
1.69
1.74
1.58
1.73
1.75
1.67
1.55
1.72
1.88
1.51
Porosity
(%)
86
57
67
70
62
77
76
76
72
69
65
55
57
59
76
68
64
81
80
74
61
65
71
65
70
79
78
79
60
57
67
58
57
62
65
59
SO
70
Rate
(g/cm2/my)
92
564
140
214
1569
592
1218
1240
1336
1318
910
1225
1275
1122
955
1318
1449
1780
1672
2277
428
823
4289
3159
3396
573
585
564
16386
17870
3274
3012
18604
4660
3314
393
150!
7572
TOC
.".ccurn.
Reference
Rz
(g/crn/rny)
18
85
32
(1) 'p.61-134
(l),p.135-283
-
26
267
89
(2) ,p.43-208
256,
298
294
290
237
196
166
135
239
343
203
2065
1187
660
548
411
10723
1927
2547
373
357
316
12453
10007
1179
873
6511
1724
961
(2) 'p.209-316
(2) ,p.61S-704
(3) ,p.2l9-312
(4) 'p.355-382
(5),p.673-794;(6),p.96l-976
(7) ,p.31-96
(5) ,p.673-794; (7) 'p.169-212
(5)
(5)
(5)
(7)
,p.673-794;(7) ,p.213-223
,p.673-794;(7) ,p.233-286
,p.673-794;(6) ,p.961-976
,p.287-396
(8),p.19-9l;(9),p.897-9l3
236
2206
28(12
(8) ,p.217-277;(D) ,p.891-9l3
K
38
38
38
38
38
38
38
38
38
36
36
34
34
36
36
34
34
34
31
34
34
34
29
23
23
23
23
330
330
330
330
336
336
336
338
344
345
345
345
345
321
321
321
227
227
228
228
282
299
319
319
319
320
320
192
192
189
189
189
189
190
190
192
192
192
19
19
19
19
19
19
19
19
19
19
19
Dole
Leg
0- 36
46- 115
115- 480
480- 700
1
1
1
1
1
0- 377
1
1
57
0-
1
1
1
4
4
3
3
1
60-123
130-200
200-300
300-400
400-500
0-159
159-254
254-463
1
0- 35
3
35- 51
1
0- 20
3
3
3
1
4
4
1
1
1
3
3
1
1
1
1
1
1
1
1
1
Lith*
70-155
31-110
10- 57
9- 24
24- 31
110-550
550-750
917-942
942-1000
0-131
131-194
0-150
250-275
192-295
0-110
0-180
180-250
250-370
370-870
0-165
165-500
(m)
Interval
76.0
13.0
21.0
22.0
37.0
6.3
25.0
20.0
100.0
56.0
5.8
1.2
35.0
20.0
7.0
11.0
2.8
4.5
22.0
22.0
25.0
100.0
107.0
150.0
230.0
27.5
115.0
9.0
7.5
110.0
160.0
160.0
160.0
110.0
70.0
57.5
100.0
100.0
(rn/my)
Sed.
Rate
1-1
1.12
.10
.39
.43
.47
.34
.81
.50
.40
.40
.28
5.55
3.18
1.40
.33
.20
.10
.10
4-2
6-5
8-8
8-9
9-9
9-9
3-2
5-5
6-6
3-2
4-2
3-2
4-4
5-5
6-6
2-1
s-4
4-4
.10
3.68
1.27
.10
.10
.S1
.91
.20
.10
.10
.86
1.97
.41
2-2
4-3
4-4
4-4
2-2
4-2
3-2
4-3
4-4
5-4
6-4
3-2
3-3
3-2
3-3
5-5
2-0
4-4
4-4
)
.43
.40
.32
.32
.45
.50
.30
TOC
(weight
Age
Pangc
1.84
1.94
1.83
1.57
1.70
1.79
1.90
1.70
1.32
1.79
2.00
1.71
1.30
1.69
1.26
1.25
1.74
1.72
1.88
1.96
1.96
1.42
1.26
1.58
1.68
79
57
53
60
55
50
69
42
55
68
48
86
86
58
86
66
60
83
59
75
43
43
57
58
48
72
(,9
71
76
85
(%)
1.48
1.44
1.50
1.39
1.24
I?orosity
C,rnjn
3094
14198
7102
648
2492
2469
9738
1239
703
2374
4963
892
759
413
103
504
5491
221
108
3721
10293
7798
19200
32700
2956
8386
4043
4453
6101
3667
Accum.
Rate
(g/cm2/my)
(c:ont inued)
(g/em3)
I .
Density
M'PflNI)l X
ii
950
1390
281
839
7887
619
1171
9810
19876
2770
219
76
136
21
50
999
372
22
9792
297S7
10879
6974
8852
15361
2873
2021
1336
2501
733
TOC
Acu,m.
flae
(g/em2/my)
(!
(I
(I
(I
'(1
(l
(l
(I
(I
(ll
(I
(l
(
(8
(8
APPCHD1X 1.
Leg
hole
Interval
LitIi
(m)
38
38
348
348
40
40
40
361
41
41
41
41
41
41
41
41
41
41
41
41
.11
41
41
4
41
41
41
42
42
43
43
43
364
364
366
366
366
366
366
366
366
366
367
367
367
367
367
367
367
370
370
370
370
381
381
386
387
387
0- 64
64- 265
727- 954
517- 583
1
1
4
4
583- 791
4
0- 100
3
110- 138
170- 200
200- 240
250- 470
480- 600
680- 720
720- 770
3
0- 170
3
3
3
3
3
3
1
170- 260
260- 320
320- 400
680- 860
910-1030
1.
1070-1140
3
200- 230
440- 620
665- 730
750- 890
200- 310
437- 475
1
953-1314
967-1086
577- 701
1
1
4
4
1
4
1
1
4
4
4
4
Scd.
Rate
(rn/my)
40.0
17.0
16.0
4.0
20.0
20.0
5.0
22.5
40.0
9.5
29.0
41.5
14.0
90.0
11.0
2.3
6.0
20.0
4.8
9.2
8.0
35.0
18.0
12.0
100.0
26.0
45.0
42.3
18.8
(Continued)
Grain
TOC
(wciglit %)
.26
.39
1.40
.98
1.95
.12
.10
.10
.14
.10
.11
.10
.10
.29
.30
.20
.57
7.80
.40
.17
.40
1.09
.61
1.22
1.70
1.09
3.90
5.00
2.10
Age
Range
Density
Porosity
Rate
lOC
Acciim.
Pate
(g/cm3)
(%)
(g/cm2/rny)
(g/cm2/my)
Accum.
2-2
4-2
8-8
1.69
1.44
63
70
1.81
55
8-8
8-8
1.81
1.90
1.63
1.77
1.69
56
3-2
4-4
4-4
4-4
6-5
6-6
6-6
7-6
3-2
4-4
6-6
50
63
54
59
4149
1218
1784
445
2538
1987
610
2437
Reference
-
1079
175
2497
43
4949
238
61
244
(IS).p.595-654;(16),p.921-h100
(l7),p.29-I82
(ll),p.35l-dSl
(l8),p.2l-ll
(18),p.l63-232
6-6
8-8
8-8
8-8
44
6-6
8-6
8-8
2-2
4-4
8-8
8-8
8-8
(lS),p.421-491
1.45
1.89
1.88
74
47
47
5308
3379
5776
3683
22525
1.78
54
2087
4382
9023
(l9Lp.293-355;(20),p.483-488
(2l),p.SO9-524
(22),p.l95-321
(22),p.323-391
APPPNI)IX I.
(Continued)
'.0
al.jtlrnlogy:
+Age Range:
l=siliceous, 2ca1careous-siliceous, 3=calcareous, 4=black shale (see Procedure, Lithology)
1=Reccnt, 2=Pleistoccnc, 3=Plioccne, 4=Mioccne, 5=Oligoccne, 6=11ocene, 7=Paleoccne, 8=Crctaceous, 9=JurassiC
Grain Accumulation Rates and Total Organic Carbon Accumulation Rates were calculated after Van Andel et al
(1975) and have an
estimated error of ±10% of the calculated value (see Procedure, Accumulation Rates).
Total Organic Carbon (bc), Porosity and Density data represent the average value for sediment intervals as calculated from
computer printouts from the Data Handling Section of the Deep Sea Drilling Project, Scripp's Institute of Oceanography,
La Jolla, Ca.
Lithology, Geologic Ages and Sedimentation Rates were determined by shipboard scientists and individual authors of the Initial
Reports of the Deep Sea Drilling Project.
The references are indicated by the table and cited below as follows:
(1) Tracey, J.I., Jr., Ct al, 1971, V.8.
(2) Hays, J.D., et al, l92, V.9.
(3) llollister. C.D., Ewing, J.1., et al, 1972, V.11
(4) Ryan, 1V.B.F., tisii, K.J., et al, 1973, V.13.
(5) Schrader, Il..J., 1973, V.18.
(6) Von I(uenc, R., Kuhn, 1.0., 1973, V.18.
(7) Kuim, 1.0., Von Iluene, It., et al, 1973, V.18.
(8) Creager, J.S., Scholl, D.1V., Ct al, 1973, V.19.
(9) Scholl, D.W., Creagor, J.S., 1973, V.19.
(10) Whitmarsh, R.8., Weser, 0.11., et a!, 1974, V.23
(ii) Kenneth, 3.1'., Iloutz, R.E., et al, 1974, V.29.
(12) Karig, 0.11., Ingle, J.C., et al, l97S, V.31.
(13) Yeats, R.S., Hart, S.R., et al, 1976, V.34.
(14) parker, P.r., Da1ie1, l.W.D., et al, 1976, V.36.
(15) Taiwani, N., Udinstev, G., et al, 1976, V.38.
(16)'Schrader, 11.3., 1976, V.38.
(37) 8olli, U.N., Ryan, W.B.F., et al, 1918, V.40.
(18) Lancelot, Y., Seibold, 11., et al, 1977, V.41.
(19) Ross, 0.A., Neprochmov, Y.P., et al, 1978, V.42.
(20) Stoffers, P., Degeiis, E.T., Trimonis, 11.S., 1978, V.42.
(21) Ilsii, K.J., 1978, V.42.
(22) Tucholke, 8.11., Vogt, P.R., et a1, 1979, V.43.
Por complete citation see References.
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