Princetonlaan 6
P.O. Box 80015
3508 TA Utrecht
TNO report
NITG 03-146-C
www.tno.nl
Palynological analysis of well G16-6 (2780m 2914m; cuttings samples) and side-track G16-6A
(2890.2m - 2942.7m ; core samples)
P +31 30 2564675
F +31 30 2564680
[email protected]
Date
August 2003
Author(s)
R. Verreussel, D.K. Munsterman and O.A. Abbink
Copy no
No. of copies
Number of pages
Number of appendices
Sponsor
NAM, Assen
Project name
Project number
005.63019
Approved
Dr. O.A. Abbink
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© 2003 TNO
TNO report | NITG 03-099-C
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Abstract
In this report to NAM, the results of a palynological study on nine cuttings samples
from the interval 2780m - 2914m of well G16-6 and 24 core samples from the sidetrack G16-6A are presented. Based on the palynology results, the following ages are
inferred:
Well G16-6 (cuttings samples)
Sample/Interval
Age
2780m
Late Ryazanian to Early Valanginian
2790m
Early Ryazanian
2800m
Portlandian
2810m
Not Diagnostic
2830m -2850m
Earliest Kimmeridgian (baylei Ammonite Zone), or older
2864m - 2914m
Permian
Side-track G16-6A (core samples)
Sample/Interval
Age
2890.20m - 2891.10m Portlandian (oppressus to primitivus Ammonite Zones)
2891.95m
Late Kimmeridgian (rotunda) to Early Portlandian (kerberus)
2892.70m
Not Diagnostic
2893.40m
Late Kimmeridgian to Early Portlandian
2897.90m
latest Callovian to Early Portlandian
2899.8m - 2923.60m Not Diagnostic
2925.80m - 2938.00m latest Callovian to earliest Kimmeridgian
probably Callovian/Oxfordian boundary interval
2938.65m
ND
2940.35m - 2942.70m Late Callovian (lamberti Ammonite Zone)
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Contents
1
Introduction
4
2
2.1
2.2
2.3
2.4
2.5
Material and Methods
Abbreviations
Samples
Sample processing
Palynological analysis
Age interpretation
5
5
5
6
6
7
3
3.1
3.1.1
3.2
3.2.1
Results
Palynology results of well G16-6 (2780m - 2914m)
Age interpretation of well G16-6
Palynology results of side-track G16-6A (2890.20m - 2942.70m)
Age interpretation of side-track G16-6A
8
8
8
9
9
4
Discussion
12
5
Comparison with well G16-3
13
6
Conclusion
14
7
References
15
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1
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Introduction
In this report to NAM, the results of a palynological study on nine cuttings samples
from the interval 2780m - 2914m of well G16-6 and 24 core samples from the sidetrack G16-6A are presented.
According to information provided by the NAM, the expected age of the interval ranges
from Ryazanian to Permian. A detailed core description of the side-track was not (yet)
available. In general terms the core consists of glauconitic sandstone at the top,
carbonaceous sandstone at the base and in between reddened intervals, conglomerates
and possible soil breccias. The objective of the analyses is to provide age assessments.
The palynological analyses were carried out by S.J. Kerstholt-Boegehold, D.K.
Munsterman and O.A. Abbink. R. Verreussel is responsible for the interpretation and
the report.
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2
Material and Methods
2.1
Abbreviations
Standard abbreviations used by TNO-NITG Paleo-Environmental Research, are
listed in Table 1
Table 1
CO
SW
CU
m
ft
LOD
FOD
2.2
Abbreviations used
Core sample
Sidewall core sample
Cuttings sample
meter
feet
Last Occurrence Datum
First Occurrence Datum
Samples
Nine cuttings samples from well G16-6 and 24 core samples from the side-track
G16-6A have been provided by the NAM for palynological analyses. Samples are
listed in Table 2.
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Table 2 Sample list of well G16-6 and side-track G16-6A
G16-6
Depth (m)
2780
2790
2800
2810
2830
2850
2864
2890
2914
2.3
Type
CU
CU
CU
CU
CU
CU
CU
CU
CU
G16-6A
Depth (m)
2890.20
2891.10
2891.95
2892.70
2893.40
2897.90
2899.80
2910.00
2915.70
2919.00
2923.60
2925.80
2928.58
2928.70
2930.85
2931.75
2933.25
2933.85
2936.25
2936.35
2938.00
2938.65
2940.35
2942.70
Type
CO
CO
CO
CO
CO
CO
CO
CO
CO
CO
CO
CO
CO
CO
CO
CO
CO
CO
CO
CO
CO
CO
CO
CO
Sample processing
All rock samples were processed at TNO-NITG, using the standard sample processing
procedures of the Laboratory of Palaeobotany and Palynology (Van Steenbergen,
1997). This involves HCl and HF treatment, heavy liquid (ZnCl2) separation and
sieving over a 18µm mesh sieve.
2.4
Palynological analysis
The microscopy analysis is according to standard procedures. The semi-quantitative
analysis includes an estimate of the main palynomorph categories, and of the
determinable sporomorphs and/or dinocysts. The remainder of the slides is then scanned
qualitatively for additional sporomorph and dinocyst taxa.
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2.5
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Age interpretation
Key-references concerning the palynostratigraphy of the Triassic to Early Cretaceous
from the North Sea region are: Costa and Davey (1992), Davey (1982), Duxbury et
al.(1999), Herngreen et al.(2000) and Powell (1992).
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3
Results
3.1
Palynology results of well G16-6 (2780m - 2914m)
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The cuttings samples are relatively rich and the palynomorphs are well preserved.
Abundant Late Jurassic/Early Cretaceous caving is present in all samples. The dominant
palynodebris type is ‘fluffy’ AOM, except for the interval 2830m - 2850m, which is
characterized by woody phytoclasts. A palynological distribution chart is added as
Appendix A.
3.1.1
Age interpretation of well G16-6
Sample/Interval
Age
2780mCU
Late Ryazanian to Early Valanginian
The age interpretation is based on:
 LOD Gochteodinia villosa
 LOD Oligosphaeridium diliculum
 LOD Tehamadinium daveyi
Remark: the common occurrence of Cicatricosisporites spp. supports the age
interpretation.
2790m – 2800m (2 CU) Early Ryazanian, or older
The age interpretation is based on:
 LOD Rotosphaeropsis thula
Remark: the age interpretation is supported by the LOD Perisseiasphaeridium insolitum
in sample 2800mCU.
2810mCU
Not Diagnostic
Abundant Early Cretaceous caving hampers a reliable age interpretation.
2830m -2850m (2 CU) Earliest Kimmeridgian (baylei Ammonite Zone), or older
The age interpretation is based on:
 LOD Striatella sp. A in Abbink 1998, in sample 2830mCU
 LOD Retitriletes undulatus (mutabilis Ammonite Zone), in sample 2830mCU
Remark: The age interpretation is supported by the LOD Trilites minutus, in sample
2850mCU. In sample 2850mCU, Early Triassic reworking is present (Platysaccus
leschiki).
Note that this interval probably correlates (in part) with the interval 2925.80m 2942.70m of the cored side-track G16-6A, which is dated ‘probably latest
Callovian to earliest Oxfordian’.
2864m - 2914m (3 CU) Permian
The age interpretation is based on:
 LOD Vittatina cpx., in sample 2864mCU
 LOD Limitisporites moersensis, in sample 2890mCU
 LOD Klausipollenites schaubergeri, in sample 2914mCU
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Palynology results of side-track G16-6A (2890.20m - 2942.70m)
The recovery in the core samples varies from completely barren to rich. The
preservation of the palynomorphs is generally good. To facilitate a comparison with the
cuttings samples of well G16-6, the palynological results are discussed from top to
bottom. A palynological distribution chart is added as Appendix B.
3.2.1
Age interpretation of side-track G16-6A
Sample
Age
2890.20mCO
Portlandian (oppressus to primitivus Ammonite Zones)
The age interpretation is based on:
 LOD abundant Cribroperidinium hansenii
 LOD common Systematophora daveyi
Remark: the presence of Rotosphaeropsis thula supports the age interpretation.
2891.10mCO
Portlandian (oppressus to primitivus Ammonite Zones)
The age interpretation is based on:
 FOD Gochteodinia villosa
Remark: Cribroperidinium hansenii is not abundant anymore.
2891.95mCO
Early Portlandian (glaucolithus to kerberus Ammonite Zones)
The age interpretation is based on:
 LOD Muderongia sp. A Davey 1979
 FOD Circulodinium compta
Remark: the presence of Glossodinium dimorphum and Senoniasphaera jurassica
supports the age interpretation.
2892.70mCO
Not Diagnostic
Apart from a few psilate trilete spores, palynomorphs are absent.
2893.40mCO
Late Kimmeridgian to Early Portlandian
The age interpretation is based on:
 FOD Classopollis echinata
Remark: only few dinoflagellate cysts are present, notably Cribroperidinium spp.
(probably Cribroperidinium globatum). The sporomorph assemblage is characterized by
Corollina spp., bisaccates and psilate trilete spores. The presence of Classopollis
echinata in combination with common Corollina spp., indicates that the oldest possible
age is Late Kimmeridgian. The youngest possible age is based on the age interpretation
of sample 2891.95mCO.
2897.90mCO
latest Callovian to Early Portlandian
The interpretation is based on:
 occurrence is Araucariacites sp. A Abbink 1998 (total range)
Remark: Dinoflagellate cysts are absent and the sporomorph assemblage is of the high
dominance - low diversity type. The dominant sporomorph types is Araucariacites sp.
A Abbink 1998.
2899.80mCO
ND
Apart from bisaccates and the odd Classopollis specimen, palynomorphs are absent.
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2910.00mCO
Barren sample.
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ND
2915.70mCO
ND
Apart from one specimen of Subtilisphaera perlucida, which is interpreted as
contamination, palynomorphs are absent.
2919.00mCO
Barren sample.
ND
2923.60mCO
Barren sample.
ND
2925.80mCO
latest Callovian to earliest Kimmeridgian
probably Callovian/Oxfordian boundary interval
The age interpretation is based on:
 occurrence Leptolepidites cf. equatibossus (total range)
 occurrence Retitriletes undulatus (total range)
Remark: dinoflagellate cysts are absent but the sample contains a rich and diverse
sporomorph assemblage. Psilate trilete spores are abundant while bisaccates, Retitriletes
undulatus, Striatella reticulata are common. The assemblage is very similar to the
assemblages from the marine interval 2940.35m - 2942.7m, which is accurately dated
Late Callovian by means of dinoflagellate cysts. Therefore, it seems most probable that
sample 2925.8mCO belongs to the same genetic unit (the J46 flooding and following
high stand phase; see Partington et al., 1993) and therefore correlates to the
Callovian/Oxfordian boundary interval.
Note the frequent occurrence of Triassic reworking (e.g. Rhaetipollis germanicus,
Riccisporites tuberculatus, Ovalipollis spp.).
Note the occurrence of questionable specimens of Cicatricosisporites spp. If in-situ
and if these specimens really belong to Cicatricosisporites, then the age of the
sample would be earliest Kimmeridgian, based on the FOD Cicatricosisporites. See
chapter 4 for an elaborate discussion.
2928.56m – 2938m (9 CO)
latest Callovian to earliest Kimmeridgian
probably Callovian/Oxfordian boundary interval
Remark: The assemblages from this interval are identical to the assemblage of sample
2925.80mCO and to the assemblages from the marine interval 2940.35m - 2942.7m,
which is accurately dated Late Callovian by means of dinoflagellate cysts. Therefore,
the same line of reasoning applies and a correlation to the Callovian/Oxfordian
boundary interval is suggested (see chapter 4 for an elaborate discussion).
Note the presence of Permian (taeniate bisaccates) and Triassic reworking throughout
the interval.
2938.65mCO
ND
Apart from some bisaccates, this sample is barren.
2940.35mCO
Late Callovian (lamberti Ammonite Zone)
The age interpretation is based on:
 LOD Durotrigia filapicata
 FOD Osmundacidites sp. A
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Remark: only few dinoflagellate cysts and sporomorphs are present. Nevertheless, the
LOD Durotrigia filapicata convincingly indicates a Late Callovian age.
2942.70mCO
Late Callovian (lamberti Ammonite Zone)
The age interpretation is based on:
 LOD Durotrigia filapicata
 LOD Lithodinia jurassica
 FOD Retitriletes undulatus
Remark: the age interpretation is supported by the LODs of Limbodinium absidatum
and Rigaudella aemula. Dinoflagellate cysts are common in this sample and the
sporomorph assemblage is rich and diverse. The marine influence may reflect a regional
flooding event, like e.g. the J46 flooding of Partington et al, (1993; see also Abbink,
1998).
Note that the possibility of reworking of the entire dinoflagellate cyst assemblage,
however unlikely, can not be ruled out (see chapter 4 for an elaborate discussion).
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Discussion
Despite the fact that many core samples from the targeted interval were available for
analysis, some questions still remain. Therefore, a short discussion on the probabilities
of the different age-scenarios seems appropriate. Based on the palynological results, a
four-fold subdivision of the core can be made:
 The interval 2890.20m – 2893.40m is marine and dated latest Kimmeridgian to
Portlandian with a high degree of confidence.
 The 2897.90m – 2899.80m is non-marine and could be anything from latest
Callovian to Early Portlandian.
 The interval 2910.00m – 2923.60m is barren, probably due to unfavourable
lithologies.
 The interval 2925.80m – 2942.70m is marine at the base and non-marine at the top.
The interval is dated Late Callovian to earliest Kimmeridgian with a high degree of
confidence and ‘probably Late Callovian to earliest Oxfordian’.
Since, the palynostratigraphic interpretation of the three uppermost intervals is rather
straightforward, the discussion concentrates on the lowermost interval (2925.80m –
2942.70m). The question is: could the dinoflagellate cysts at the base be reworked?
Especially since specimens of Cicatricosisporites occur at the top of the interval
(2925.80m), which are indicative of a Kimmeridigian, or younger, age. The four most
obvious options are:
1) The interval is not one genetic unit but two (an earliest Kimmeridgian and a latest
Callovian unit), separated by a hiatus.
2) The interval is entirely earliest Kimmeridgian and the dinoflagellate cysts at the
base are reworked.
3) The dinoflagellate cysts at the base are in-situ and the Cicatricosisporites
specimens at the top are in fact precursors of the genus (a transitional type to
Striatella), or the range base of Cicatricosisporites is much older than hithereto
accepted. Therefore: the entire interval is ‘probably Late Callovian to earliest
Oxfordian’.
4) The dinoflagellate cysts at the base are in-situ and the specimens of
Cicatricosisporites at the top are due to contamination. Again: the entire interval is
‘probably Late Callovian to earliest Oxfordian’.
The following line of reasoning has been applied in this report: the interval is one
genetic unit because the sporomorph assemblages are very uniform throughout the unit
(including the occurrence of Triassic reworking). Furthermore, the dinoflagellate cysts
at the base are not considered as reworking because:
 it is a complete and characteristic Late Callovian assemblage,
 the lowermost sample contains the richest and most diverse dinoflagellate cyst
assemblage, which seems logical from a sequence stratigraphic view (sedimentation
starts off with a marine flooding, followed by a regressive high stand phase),
 the dinoflagellate cysts do not occur higher up, which would seem logical in the case
of reworking (the Triassic reworking, f.i. occurs continuously throughout the
interval).
Therefore, the questionable Cicatricosisporites types are considered as contamination
or precursor types (options 3 or 4) and the age of the entire interval is probably Late
Callovian to earliest Oxfordian.
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Comparison of well G16-6A with well G16-3
As requested by NAM, the palynology results of the cored side track G16-6A have been
compared with the palynology results of a cored section from the nearby well G16-3
(LPP report 9815/16/9820/9829).
Palynology results of well G16-3
In well G16-3 an approximately 70m thick interval consisting of sandstones and shales
is sandwiched between Late Ryazanian shales and Permian caprock. The 25m thick
cored section is from the top of the sandwiched unit (interval 2710.4m – 2735.6m). The
interval has been dated Early Kimmeridgian, based on the LODs Punctatisporites spp.,
Varirugosisporites tuberosus, Retitriletes undulatus and the FOD Cicatricosisporites
spp. The paleoenvironment is interpreted as paralic, possibly non-marine, based on the
absence of dinoflagellate cysts.
Comparison of well G16-3 with side-track G16-6A
The similarity of the sporomorph assemblages from the core of well G16-3 to those of
the interval 2925.80m – 2942.70m from the side-track G16-6A is very striking
(dominance of Calliasporites, Araucariacites, Densoisporites and psilatrilete spores, in
combination with frequent Retitriletes undulatus, Striatella reticulatus and very rare
Cicatricosisporites spp.). The only difference is the presence of dinoflagellate cysts at
the base of the side-track. The fact that (very rare) Cicatricosisporites spp. also occur in
the core of well C16-3, rules out the possibility of contamination (option 4). All other
options remain open and the line of reasoning followed in this report does not change
(option 3 as most probable). Note, however, that in between the core of well G16-3 and
the Permian caprock, another 40m of rock are present (including shales!) which have
not been dated.
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Conclusion
Based on the palynological results, the following ages are inferred:
Well G16-6 (cuttings samples)
Sample/Interval
Age
2780m
Late Ryazanian to Early Valanginian
2790m
Early Ryazanian
2800m
Portlandian
2810m
Not Diagnostic
2830m -2850m
Earliest Kimmeridgian (baylei Ammonite Zone), or older
2864m - 2914m
Permian
Side-track G16-6A (core samples)
Sample/Interval
Age
2890.20m - 2891.10m Portlandian (oppressus to primitivus Ammonite Zones)
2891.95m
Late Kimmeridgian (rotunda) to Early Portlandian (kerberus)
2892.70m
Not Diagnostic
2893.40m
Late Kimmeridgian to Early Portlandian
2897.90m
latest Callovian to Early Portlandian
2899.8m - 2923.60m Not Diagnostic
2925.80m - 2938.00m latest Callovian to earliest Kimmeridgian
probably Callovian/Oxfordian boundary interval
2938.65m
ND
2940.35m - 2942.70m Late Callovian (lamberti Ammonite Zone)
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References
Abbink, O.A., 1998
Palynological investigations in the Jurassic of the North Sea region. LPP
contributions series, No 8. (PhD thesis). LPP Foundation, University of Utrecht.
Costa, L.I. and Davey, R.J., 1992.
Dinoflagellate cysts of the Cretaceous System. In: Powell, A.J. (ed.), A
Stratigraphic Index of Dinoflagellate Cysts: 99-154.
Davey, R.J., 1982.
Dinocyst stratigraphy of the latest Jurassic to Early Cretaceous of the Haldager
No. 1 borehole, Denmark. Geol. Surv. Denm. Ser. B, 6: 58pp.
Duxbury, S., Kadolsky, D. and Johansen, S., 1999.
Sequence stratigraphic subdivision fo the Humber Group in the Outer Moray
Firth area (UKCS, North Sea). In: Jones, R.W. and Simmons, M.D. (eds)
Biostratigraphy in Production and Development Geology. Geol. Soc. Spec. Pub.,
152: 23-54.
Herngreen, G.F.W., Kerstholt, S.J. and Munsterman, D.K., 2000.
Callovian - Ryazanian (‘Upper Jurassic’) palynostratigraphy of the Central
North Sea Graben and Vlieland Basin, The Netherlands. Mededelingen
Nederlands Instituut voor Toegepaste Geowetenschappen TNO, 63: 99pp.
LPP report 9815/16/9820/9829
Palynostratigraphy of wells G13-1, G16-1, G16-2 and G16-3. LPP projects 9815,
9816, 9820 and 9829 carried out for NAM B.V., september 1998. LPP, Budapestlaan
4, 3584 CD, Utrecht.
Partington, M.A.P., Copestake, P., Mitchener, B.C. and Underhill, J.R. 1993.
Biostratigraphic correlation of genetic stratigraphic sequences in the Jurassic lowermost Cretaceous (Hettangian - Ryazanian) of the North Sea and adjacent
areas. In: Parker, J.R., (Ed.), Petroleum Geology of Northwest Europe:
Proceedings of the 4th Conference: 371 - 386.
Powell, A.J., 1992.
Dinoflagellate cysts of the Triassic System. In: Powell, A.J. (ed.), A
Stratigraphic Index of Dinoflagellate Cysts: 1-6.
Van Steenbergen, A., 1997.
Palynolological Techniques for Rock Sample Processing. Laboratory of
Palaeobotany and Palynology Internal Report.
TNO report | NITG 03-099-C
A
Palynological distribution chart of well G16-6
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TNO report | NITG 03-099-C
B
Palynological distribution chart of well G16-6A
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