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European Journal of Applied Sciences – Vol. 11, No. 3

Publication Date: June 25, 2023

DOI:10.14738/aivp.113.14300.

Apanpa, K. A., Adeagbo, O. A., Oladimeji, R. G., & Adesope, O. A. (2023). Palynozonation of Akukwa-2 Well, Anambra Basin:

Implications for Age and Paleoenvironment. European Journal of Applied Sciences, Vol - 11(3). 342-359.

Services for Science and Education – United Kingdom

Palynozonation of Akukwa-2 Well, Anambra Basin: Implications

for Age and Paleoenvironment

Kazeem Abidemi Apanpa

Department of Geology, The Polytechnic, Ibadan, Nigeria

Olusola Ayoade Adeagbo

Department of Geology, The Polytechnic, Ibadan, Nigeria

Razak Gboyega Oladimeji

Department of Geological Sciences,

Osun State University, Osogbo, Osun State, Nigeria

Olajumoke Adebukola Adesope

Department of Geology, The Polytechnic, Ibadan, Nigeria

ABSTRACT

Palynological examination of twenty (20) ditch shale samples from sedimentary

succession penetrated by Akukwa-2 Well at depth interval of 3,296 - 3,850 m was

undertaken to investigate the occurrence of Palynomorph in the sediments of

Anambra Basin with a view to determining the age of the sediments and reconstruct

the depositional paleoenvironment. Standard Palynological procedure was

followed and the samples were processed using the conventional acid maceration,

alkali treatment and staining methods. The oxidized residues were sieved with

5micron nylon sieves using digital Sonifier 450 machine and mounted on glass

slides with Norland adhesive gel. Laborlux 12 (Ernst Leitz) transmitting light

microscope was used for identification and counting or the palynomorphs. The

palynological analysis was done using the population and species of pollen grains,

spores and dinoflagelate. The analyzed palynological slides yielded forty-nine (49)

palynomorphs species identify in the ditch samples, forty (40) were Miospores

(pollen and spores) and nine were Dynocysts. However, some diagnostic forms that

are stratigraphically useful are present and are used for the palynozonation.

Delineation of the well section produced three main palynological zones based on

stratigraphic distribution. Zone 1 characterized by the quantitative base

appearance of Triorites Africaensis Assemblage indicating Marginal Marine

paleoenvironment and of Turonian age; Zone 2, marked by Droseridites Senonicus

assemblage also of Marginal Marine but of Coniacian age, Zone 3, marked by

Milfordia spp. Acme Zone, purely Marine and of Campano- Maastrichtian age. The

study further reveled that Palynomorph recovery in Akukwa-2 well was not that

impressive both in terms of abundance and preservation. In most cases, the

macerals present seems to indicate high geothermal effect suggesting that some of

the kerogen might have been overcooked to imply inability to generate

hydrocarbon or such generated hydrocarbon have turned into carbon.

Keywords: Anambra Basin, Palynomorphs, Paleoenvironment, Campano- Maastrichtian

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343

Apanpa, K. A., Adeagbo, O. A., Oladimeji, R. G., & Adesope, O. A. (2023). Palynozonation of Akukwa-2 Well, Anambra Basin: Implications for Age and

Paleoenvironment. European Journal of Applied Sciences, Vol - 11(3). 342-359.

URL: http://dx.doi.org/10.14738/aivp.113.14300.

INTRODUCTION

In this ever-changing economic and political climate, petroleum explorationists and field

development geologists are being asked to find more oil and develop older reserves [1] This

increasing search for hydrocarbon has led to the application of improved technologies such as

the use of Palynology and Paleo-environmental analyses in locating the required stratigraphic

sequences and structures. The use of improved technologies helps in reducing cost of drilling

or payback for drilling and production cost [2].

These technologies will assist in better delineation of paleo-environmental reconstruction,

chronostratigraphic framework, stratigraphic units and depositional environment. The Benue

Trough (Fig. 1) is a unique rift feature on the African Continent in that it occupies an intra- continental position and has a thick compressionally folded Cretaceous supracrustal fill which

is generally divided into Lower, Middle and Upper Benue Trough [3, 4, 5, 6, 7, 8, 9, 10].

Palynology was once limited to the study of spores and pollen. However, it has recently been

extended to encompass other organic-walled microfossils, collectively termed palynomorphs

[1]. The palynological method had been used to determine the Age and Paleo-environment of

Gongola Basin [11]. The method was also used on Ubaije-1 well samples to delineate

stratigraphy, Age and Paleo- environment of Awgu Shale of Anambra Basin [12]. [13] studied

the occurrence of palynomorphs in the sediments of Anambra Basin obtained from Amansiodo- 1 well and used the results to arrive at the age and paleoenvironment of the Shale Samples. The

aim of this study is to predict the depositional environment, determine the ages of the

sediments and chronostratigraphic correlation across the basin. By studying the fossils in many

wells, a geologic model for the area can be built up. Such paleogeographic maps, combined with

seismic profiles and other geologic data sets, are the tools used in the search for hydrocarbons.

Location of the Study Area

The basin is roughly triangular in shape and covers an area of about 40,000 square kilometers

with sediment thickness increasing southwards to a maximum thickness of 12,000m in the

central part of Niger Delta. The basin lies between latitudes 5.00N and 7.00N and longitudes

7.00E and 8.00E.

Anambra Basin is located west of the lower Benue Trough and often considered newest

formation from the Benue Trough [14]. The basin is bounded to the south by the Niger Delta

Basin hinge line [15]. It extends north-westward into the Niger valley, northward to the Jos

massif and north east-ward into Lafia. The eastern and western limits of the basin are defined

by Abakaliki Anticlinorium and Ibadan massif, respectively [15]. The well of interest falls

between Longitude 7008’32’’E and Latitude 5054’48’’N as shown in Figure 2.

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European Journal of Applied Sciences (EJAS) Vol. 11, Issue 3, June-2023

Figure 1: Regional Stratigraphy of the Anambra Basin showing sampling location [16].