Stable Carbon Isotopes: a Powerful
Correlation Tool for Clastic Rocks
Elisa Guasti1, Roel Verreussel1, Timme Donders1, Tom van Hoof1
1TNO-Petroleum
Geosciences, Utrecht, the Netherlands
[email protected]
INTRODUCTION
Stable isotope geochemistry is a rapidly evolving branch of science. As an innovative application to E&P, it focuses on
enhancing correlation at a local, regional and a global scale. The combination of biostratigraphic data with the
independent proxy from the stable isotope analyses provides excellent opportunities for chronostratigraphic calibration.
EARLY TOARCIAN OAE
TNO is currently developing novel techniques to utilize the biostratigraphic residues
for stable isotope analysis. A δ13C curve in the Lower Jurassic Dunlin Group of the
northern North Sea displayed a spectacular shift (~5 per mil) towards more negative
values in the deltaic Cook Formation. In combination with the Early Toarcian age
derived from palynology, a correlation with the Toarcian Carbon Isotope Event (CIE) is
possible (Fig. 1). The Toarcian CIE is associated with the organic rich source rocks
known as Posidonia Shale or Jet Rock. In another example, TNO carried out a
palynological and stable isotope study on the Posidonia Shale in the Netherlands. In
this shale gas project, the stable isotope trend of well LOZ-01 matched one-on-one
with the stable isotope trend from the well-calibrated Dotternhausen section in the
type area, more than 500 km away (Fig. 2).
LOZ-01
TOARCIAN
181
182
Early
Middle
180
ps
ila
tu
s
183
ip
ol
le
nit
es
sp
p.
oll
is
d1
3C
Sp
he
r
la
ss
op
C
G
R
GR
Dotternhausen (Röhl et al., 2001)
Age
Ma
δ13C
Fig. 2 Stable isotope trend of the Posidonia Shale in well LOZ-01
(onshore The Netherlands), correlated to the Posidonia
in the type area (South Germany)
2500
2510
2520
Drake
2530
2540
2550
2560
Cook-3
2570
THE PALEOCE-EOCENE BOUNDARY
2580
2590
Cook-2
2600
In the Suriname Coastal Plain, a high Gamma Ray interval
occurs at the top of the Saramacca Fm. Based on
palynological data, this interval is suggested to correlate with
the hyperthermal at the base of the Eocene. Stable isotope
analyses on the palynological residues revealed a major
negative shift in the high GR interval, allowing correlation to
the Paleocene Eocene Thermal Maximum. Since the P/E
GSSP is in fact based on the δ13C signature this is a highly
relevant result.
2610
2620
2630
2640
2650
Cook-1
2660
2670
2680
Burton
2690
Amundsen
2700
40
56
72
88
104
120 0
10
20
30
40
50 0
8
16
24
32
40-30,0
-28,0
-26,0
-24,0
Fig. 1 Stable isotope trend of the
Cook Fm, North Sea, correlated to
the Toarcian CIE.
PERMO-CARBONIFEROUS BARREN DEPOSITS
δ13C
GR
600
δ13C
For the first time, we apply stable isotope
in combination
to biogenic silica microfossils as stratigraphic tool in the
Permo-Carboniferous sequences in the SNS and in the Middle
East. Stratigraphic correlations in these deposits are
notoriously difficult to determine due to a lack of effective
correlation tools in the red bed deposits. The combination of
the stable isotopes and biogenic silica improves existing
geological correlations and the positioning of regional
unconformities.
620
640
660
680
Coesewijne
700
720
740
760
780
800
820
840
860
880
900
920
940
960
Upper
Saramacca
980
1000
1020
1040
1060
1080
1100
1120
1140
1160
1180
Middle
Saramacca
Lower
Saramacca
1200
1220
1240
1260
1280
1300
1320
1340
1360
1380
1400
1420
Nickerie
1440
1460
1480
1500
0
30
60
90
120
150-32.0
-30.0
-28.0
-26.0
-24.0
-22.0