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High-resolution Biostratigraphic Studies of Step-1 Well, Offshore, Western Niger Delta

M. E. Nton
M. E. Nton
 y 
S. O. Famori
S. O. Famori
   | 06 abr 2021
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Article Category: Original scientific paper
Publicado en línea: 06 abr 2021
Páginas: 135 - 148
Recibido: 02 dic 2020
Aceptado: 07 dic 2020
DOI: https://doi.org/10.2478/rmzmag-2020-0014
Palabras clave
© 2020 M. E. Nton et al., published by Sciendo
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Figure 1

Geological map of Western Niger Delta showing the approximate study area (modified from [5]).
Geological map of Western Niger Delta showing the approximate study area (modified from [5]).

Figure 2

Stratigraphic succession of the Niger Delta [7].
Stratigraphic succession of the Niger Delta [7].

Figure 3

Lithological description of STEP-1 well.
Lithological description of STEP-1 well.

Figure 4

Foraminiferal distribution chart of STEP-1 well.
Foraminiferal distribution chart of STEP-1 well.

Figure 5

Calcareous nannofossil distribution chart of STEP-1 well.
Calcareous nannofossil distribution chart of STEP-1 well.

Figure 6

Palynomorphs distribution chart of STEP-1 well.
Palynomorphs distribution chart of STEP-1 well.

Figure 7

Plot of A. aureum/M. annulatus against depth (1,853–2,146 m).
Plot of A. aureum/M. annulatus against depth (1,853–2,146 m).

Figure 8

Plot of A. aureum/M. annulatus against depth (2,170–2,438 m).
Plot of A. aureum/M. annulatus against depth (2,170–2,438 m).

Figure 9

Photomicrographs of foraminifera, calcareous nannofossil and Palynomorps recovered from STEP-1 well.
Photomicrographs of foraminifera, calcareous nannofossil and Palynomorps recovered from STEP-1 well.

Age deductions for STEP-1 well

Depth (m) Age (Ma) Microfossil Bioevents
1,926 5.0 Foraminifera FDO Cyclammina cf. minima
1,963 5.8 Nannofossils Maximum flooding surface (MFS)
1,987 5.8 Foraminifera Peak faunal abundance (MFS)
2,097 6.3 Nannofossils Sequence boundary
2,316 7.0 Nannofossils MFS

Chronostratigraphic position of STEP-1 well

Ma Standard chronostratigraphy
Period Epoch Age/stage This study
1 Quaternary Holocene Taranian
2
Pleistocene Ionian
3
Calabrian
4 Neogene Pliocene Gelasian
5 Piacenzian
6 Zanclean
7 Miocene Messinian
 STEP-1 well
8
9 Tortonian
10

Calcareous nannofossils biostratigraphy of STEP-1 well

Depth (m) Downhole occurrence of calcareous nannofossils Age (Ma) Haq et al. (1988) NP zones (Martini, 1971) Inferred relative ages
1,841 First sample analysed Late Miocene to early Pliocene
1,902 Presence of Ceratolithus cristatus NN 12
1,914 Presence of Ceratolithus cristatus
1,926
1,939 FDO: Discoaster quinqueramus 5.8
1,963 Maximum flooding surface
2,292 FDO: Discoaster berggrenii
2,316 Maximum flooding surface, Presence: Discoaster quinqueramus 7.0 NN 11
2,438 TD

Palynostratigraphy of STEP-1 well

Depth (m) series Sub-series Gemeraad et al. (1968) Evamy et al. (1978)
 Bioevents
Zone Sub-zone
1,829 Miocene Late Miocene Echitricolporites Spinosus zone P 800 P 840 Quantitative base occurrence of Cyperaceaepollis spp
1,981
2,134
2,204 P 830
2,286
2,438

Foraminferal biostatigraphy of STEP-1 well

Depth (m) Age Planktonic zone Benthonic foram zone Bioevents
1,8531,926 Early Pliocene N18 Indeterminate FDO Valvulina flexilisCyclamina cf. minima 5.0 Ma MFS
1,9872,0972,438 Late Pliocene N17 and older Cyclamina cf. minina Indeterminate Peak fauna abundance 5.8Ma MFS

Harmonized biostratigraphic chart of STEP-1 well

Depth (m) Epoch Age P zone B zone N zone Pa zone Pa zone and sub-zone Bioevents
1,900 Early Pliocene ZANCLEAN N18 Cyclamina minima NN 12 Echitricolporites Spinosus P800 P840 FDO Valvulina flexilis
1,950 Presence of Ceratolithus cristatus
2,000 Presence of Ceratolithus armatus
2,050 FDO Cyclammina cf. minima (5.0Ma MFS)
2,100 FDO Discoaster quinqueramus
2,150 Late Miocene MESSIAN N 17 and older NN 11 P830 5.8 Ma MFS
2,200 Peak faunal abundance (5.8 Ma MFS)
2,250 6.3 Ma SB
2,300 Quantitative base occurrence of Cyperaceaepollis spp
2,350 Discoaster beggrenii
2,400 7.0 Ma MFS
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