The principles application of carbon and oxygen isotope in geological studies . (Paleoceanography, paleoclimatology, Dating, Mineral exploration, etc

1. CARBON AND OXYGEN ISOTOPES:
PRINCIPLES AND APPLICATION IN
GEOLOGICAL STUDIES
BY
OLADIMEJI AKINSILE
UNIVERSITY OF ILORIN, ILORIN,
NIGERIA

2. PRESENTATION OUTLINE
 Introduction
 Objectives of the review
 Principles and instrumentation
 Fractionation processes
 Application of carbon and oxygen in geological studies
 Selected case studies
 Conclusions

3.  What is isotope ?
 Basics of isotope
 Stable and unstable isotopes

4. TABLE 1: ATOMIC WEIGHT OF CARBON(C)) and OXYGEN(O)
ISOTOPE ( Walker et al 1989)
ELEMENT ISOTOPE ATOMIC
WEIGHT(amu)
ABUNDANCE
(%)
CARBON ( 6) 12C 12.00000 98.90
13C 13.00335 1.1
OXYGEN (8) 16O 15.9994 99.76
17O 15.994915 0.04
18O 17.999160 0.20

5. OBJECTIVES OF THE REVIEW
 To discuss the principles and instrumentation
involved in the carbon and oxygen isotope.
 To discuss the application of carbon and oxygen
isotopes in geological studies.

6. PRINCIPLES
Element occur in the earth system in multiple
isotopes , both stable and unstable
Proportions of stable isotopes in the earth are
constant
The lighter isotopes (16O , 12C ) are more reactive
than heavier isotopes (18O, 13C)
In higher temperature,lighter isotopes are
preferentially lost.

7. MEASURING ISOTOPES
Prepare sample
Introduce sample
Convert to gas
Flow through GC to seperate
CO2
Inject reference gas to IRMS
Inject sample to IRMS
Figure 1:Schematic diagram of Isotope-ratio mass spectrometer used to measure stable isotope
ratios, with gas bench in foreground After Williams, 1998.

8. ISOTOPE STANDARD
 VSMOW – Vienna standard mean ocean water (bunch of
ocean water kept in austria) . The standard for the oxygen
isotope is 0.002004
 PDB- Pee Dee Belemnite – Fossil of a belemnite from the Pee
Dee formation in canada . The standard carbon oxygen
isotope is 0.011056
 CDT- Canyon Diablo Troilite
Source: After J. Hoefs (1980) (Stable isotope Geochemistry)

9. FRACTIONATION PROCESSES
This is a reaction or process which selects for
one of the stable isotope of a particular
elements. If the process selects for the heavier
isotope. The reaction product is heavy and vice
versa
 Types
Equilibrum isotope fractionation
kinetic isotope fractionation

10. Calculations
It is given as per mil (‰) difference (δ)
compared to a standard.
For Oxygen isotope this is calculated as
For carbon isotope it is calculated as
The result is multiplied by 1000 simply to make the resulting
ratio more meaningful

11. APPLICATIONS
 Geochronology
it is assumed that the atmosphere is in equilibrum with respect to 14C poduced by
the cosmic ray flux which is equal to the rate of decay of 14C , so that the abundance
in the atmosphere remains constant
N = N = Noe-lt
Where No is the number of atoms present at t = 0. This is the basic form of the
radioactive decay equation.
N = number of atoms left
t = time when organism from which the sample was taken died
Fig 2 : diagram showing the 14C
dating curve After Libby and Arnold
(1949)

12.  Paleoenvironment :To distinguish between the sedimentary rocks of marine
origin and those deposited in terrestial environment.
Fig 3 :Distribution of δ18O and δ13C values in various types of marine carbonates . After
milliam, . J. D., 1974)

13.  Geothermometry – the utility of oxygen isotopes has to do with
fractionation that occurs during evaporation and condensation of water and
CaCO3
T(°C) = 16.9 – 4.38 (dc –dw) + 0.10(dc-dw)2
where dc = the equilibrum oxygen isotope of calcite
dw= oxygen isotopic composition of the water from which the
calcite was precipitated
 Paleoceanography
• Paleoclimate reconstruction
Fig 4: Diagram showing δ18O
trends in the glacial-interglacial
swings in the longterm record
cooling of the deep ocean. K.G.
Miller et al.,
Paleoceanography 2, 1, 1987.

14. Fig 5: Schematic illustration of the
relationship between continental
glaciations and the 18O content of
ocean water during the last 150,00
years .
*Note that 18O values become less
negative (more heavy oxygen) during
stages of continental glaciation and
lowered sea level .After Williams et
al., 1988

15.  Hydrothermal ore deposit. This is the large interaction of
cooling magma and large volume of meteoric water helps in
understanding its origin and related alteration in the country
rocks which has a deep seated origin.Low δ13C value of -4
to -12 suggesting deep seated origin. While most carbonates
minerals formed early in hydrothermal veins have value of -6
to -9 but those formed in paragnetic sequence are rich in 13C
and may have positive value.

16.  Fossil fuel
it can be used to detect fossil fuel contribution to the
atmosphere because the burning of fossil fuel has
increased the CO2 content of the atmosphere and has
caused immeasurably decrease in 13C value because
of the enrichment in 12C.

17. To achieve maximum stratigraphic precision and age control
Fig 6: showing carbon isotope stratigraphy of bulk carbonates sediments
from deep sea drilling project (After shackleton, N.J and M.A Hall, 1984)

18. Figure 7: Geological map of dahomey embayment Nigeria part
Carbon and oxygen isotopic compositions and diagenesis of the Ewekoro
Formation in the eastern Dahomey Basin, southwestern Nigeria
O.A Adekeye, S.O Akande. R.B. Bale and , B.D. Erdtmann 2005

19. Table.2 : Regional Stratigraphic Setting of Dahomey Basin (Modified from Idowu et al., 1993)

20. Table 3 . Carbon and Oxygen isotopic compositions of the selected Ewekoro Carbonates in Sagamu Quarry
Sample No Locations Age Sample description %o PDB
δ13C
%o PDB
δ18O
Unaltered oyster shells
S-1ai
S1aii
S3a
S13ai
S13aii
Sagamu
quarry Paleocene Unaltered oyster
shell
0.86
0.91
0.87
0.59
0.62
-4.46
-4.31
-4.49
-4.51
-4.41
Unaltered sea urchins
S1b
S3b
S13b
Sagamu Quarry
Paleocene
Unaltered sea
urchins
1.01
0.14
-0.14
-3.41
-4.12
-4.83
Whole sample
S5a
S10a
S11a
S12a
S18a
S18aii
S25a
S28a
Sagamu Quarry
Paleocene Bulk sample
-1.39
0.07
-0.23
0.34
- 0.83
- 0.58
- 0.24
- 0.23
-4.77
-4.39
-4.65
-5.37
-5.37
-5.13
-5.06
-5.02
Recrystallized calcite sample
S1c
S3c
S5b
S10b
S11b
S12b
S13c
S20s
Sagamu Quarry
Paleocene Recrystallized
calcite
0.07
-1.22
-0.80
-1.18
-1.02
0.12
-2.44
-2.26
-4.46
-6.32
-7.34
-7.68
-6.54
-6.24
-7.12
-7.53

21. Fig 8: Plot showing carbon and oxygen
composition in the Ewekoro Formation

22. RESULT AND INTERPRETATION
From the table, it is concluded that the carbon and oxygen isotopic
compositions of the carbonate rocks vary from -3.41 ‰ to -7.68 ‰ δ18O
PDB and ±1.01 ‰ to -2.44 ‰ δ13C PDB for tertiary sea water suggest that
the heavier oxygen and carbon are recorded in the unaltered carbonates and
the lighter fractions in the late stage recrystallized carbonates, due to the
indicative of isotopic fractionation.
Estimated formational paleotemperature for the carbonates vary from
26.650c to 32.520c based on the calculations from and the unaltered
carbonates δ18O values indicating only very limited burial and lack of
severe hydrothermal alterations .

23. CASE STUDY TWO
• Depositional environment and carbon/oxygen isotopic composition of the
Paleocene carbonates exposed around Kalambaina, Sokoto basin, Nigeria
O.A Adekeye, S.O Akande, B.D and Erdtmann, B.D (2013)
Figure 9: Geological sketch map of northwestern Nigeria showing Kalambaina
Formation type locality (modified from Obiosio et al., 1998).

24. Figure 10: Generalised stratigraphic setting of the Sokoto
Basin (modified from Obiosio et al., 1998)

25. Table 4: showing carbon and oxygen isotopic composition of the selected kalabaina
carbonates in kalambaina quarry
Carbon and oxygen isotopic composition vary from -5.29%o to -6.55%o δ18O
PDB and -1.24%o to -3.40%o PDB δ13C in the whole rock

26. RESULT AND INTERPRETATION
The lighter oxygen and carbon fractions in the samples is a reflection of the
depletion of heavier isotope of oxygen and carbon as a result of late stage
recrystallization, which suggests that carbonates of the Kalambaina
Formation were deposited in shallow marine environment during the
Paleocene marine transgression into the Sokoto basin. No evidence of
hydrothermal alteration was observed in the carbonates, brings organic rich
water with low 13C/12C ratio (δ13C) into the shallow marine water
environments of the primary carbonate build up (Marshall, 1992).

27. Fig 11: Synthetic sedimentological log of Jibou
Formation in Rona area and location of samples
under study (R1-R46 )
Rona Limestone is a lens shaped body
located in the NW of transylvania having a
local development. The classic outcrop is
located westwards from the
neighbourhood of jibou and rona , the
deposit has maximum thickness of about
300m,towards the NE, it gradually
becomes thinner until it disappears in the
area of caselor and Gardbrookes (Popescu,
1984)
The age of Rona Limestone is Late
Paleocene - Early Eocene (Gheerbrant et
al., 1999).
GEOLOGICAL BACKGROUND
CARBON AND OXYGEN ISOTOPE RATIOS IN RONA LIMESTONE,
ROMANIA
STELA CUNA1, DANA POP2, ALEXANDRU HOSU2

28. METHODOLOGY AND RESULT
Carbon and oxygen isotope measurements were done on 10 samples and
the carbon 13 range from δ13C (-3.12 to -6.78) and δ18O (-9.41 to -14.13)
Table 5 : Showing the carbon and oxygen isotopic data

29. • Table 5: carbon and oxygen isotope ratios in carbonate rocks according to
previous references

30. Fig. 12:Distribution of δ18O vs. δ13C (‰ PDB) values in various types of
carbonate rocks, including this study (After Veizer, 1983)

31. RESULT AND INTERPRETATION
The oxygen and carbon isotope data indicate a freshwater
depositional environment with the δ13C mean value (-4.96‰
PDB) is, generally, representative for fresh-water carbonates of
the Tertiary period.

32. Conclusion
 Isotopic variations in stable and non stable isotopes are often produced by
exchange reactions, kinetic reactions in biological system such as
evaporation or diffusion. The fractionation of stable isotope decreases with
increase in temperature hence stable isotopes show greater fractionation in
sedimentary systems than in magamatic rocks.
 Carbon and oxygen isotope has a very wide application in geological
studies including, the study of igneous, sedimentary and metamorphic
rocks, application to temperature (paleothermometry), study of
hydrothermal ore deposits, determination of fossil fuel to know the various
carbon contents, and to distinguish marine from non marine carbonates.

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