\documentclass[10pt]{article}

\usepackage{fullpage}
\usepackage{setspace}
\usepackage{parskip}
\usepackage{titlesec}
\usepackage[section]{placeins}
\usepackage{xcolor}
\usepackage{breakcites}
\usepackage{lineno}
\usepackage{hyphenat}





\PassOptionsToPackage{hyphens}{url}
\usepackage[colorlinks = true,
            linkcolor = blue,
            urlcolor  = blue,
            citecolor = blue,
            anchorcolor = blue]{hyperref}
\usepackage{etoolbox}
\makeatletter
\patchcmd\@combinedblfloats{\box\@outputbox}{\unvbox\@outputbox}{}{%
  \errmessage{\noexpand\@combinedblfloats could not be patched}%
}%
\makeatother


\usepackage{natbib}




\renewenvironment{abstract}
  {{\bfseries\noindent{\abstractname}\par\nobreak}\footnotesize}
  {\bigskip}

\titlespacing{\section}{0pt}{*3}{*1}
\titlespacing{\subsection}{0pt}{*2}{*0.5}
\titlespacing{\subsubsection}{0pt}{*1.5}{0pt}


\usepackage{authblk}


\usepackage{graphicx}
\usepackage[space]{grffile}
\usepackage{latexsym}
\usepackage{textcomp}
\usepackage{longtable}
\usepackage{tabulary}
\usepackage{booktabs,array,multirow}
\usepackage{amsfonts,amsmath,amssymb}
\providecommand\citet{\cite}
\providecommand\citep{\cite}
\providecommand\citealt{\cite}
% You can conditionalize code for latexml or normal latex using this.
\newif\iflatexml\latexmlfalse
\providecommand{\tightlist}{\setlength{\itemsep}{0pt}\setlength{\parskip}{0pt}}%

\AtBeginDocument{\DeclareGraphicsExtensions{.pdf,.PDF,.eps,.EPS,.png,.PNG,.tif,.TIF,.jpg,.JPG,.jpeg,.JPEG}}

\usepackage[utf8]{inputenc}
\usepackage[ngerman,english]{babel}



\usepackage{float}








\begin{document}

\title{Vegetation Dynamics vs. Sediment Supply During the Late Quaternary:
Paradigm of Sea Level Change and Two Distinct Time-Bound Stages of the
Niger Delta Coastal Evolution}



\author[1,1]{Onema Adojoh}%
\affil[1]{Case Western Reserve University}%


\vspace{-1em}



  
  \date{June 15, 2024}


\begingroup
\let\center\flushleft
\let\endcenter\endflushleft
\maketitle
\endgroup





\selectlanguage{english}
\begin{abstract}
This study examines the impact of climate-sea level controls on the
vegetation and evolution of the Niger Delta during the Late Quaternary.
The extraneous controls on the environment outlined in this context
confirm a direct link between vegetation dynamics (pollen data),
sediment supply, and the landscape evolution of the Niger Delta between
20 ka and 6.5 ka. Two phases of sedimentation are recognized based on
multiple proxies analyzed in three gravity cores obtained from the
shallow offshore at \textasciitilde{}40 m water depth. Phase I records
abundant occurrences of Poaceae, Cyperaceae, and Podocarpus pollen from
a dry hinterland, charred grass cuticles, nonmarine alga Pediastrum,
high Ti/Zr ratio, and lower sedimentation from 20-11.7 ka. Phase II
records an expansion of mangrove vegetation, high Fe/S ratio, and
increase in planktonic foraminifera between 11.7 ka and 6.5 ka. This
second phase is attributed to sea-level rise and higher sedimentation
during the development of delta plain and mangrove vegetation on the
gently sloping shelf. These sequential records provide a new clue about
the link between the evolutionary stages of the Niger Delta landscape
and vegetation dynamics during two distinct time-bound intervals, which
potentially delineate the boundary between two Marine Isotope Stages:
MIS2 (late glacial period) and MIS1 (interglacial period). Keyword: Sea
level- climate change, Late Quaternary, mangrove pollen,
biogeochemistry, Niger Delta, landscape evolution.%
\end{abstract}%



\sloppy


Geochemical vs. palynological records during the Late Quaternary:
Paradigm of sea level change and two distinct time-bound stages of the
Niger Delta evolution

Onema C. Adojoh\textsuperscript{abc}, Fabienne
Marret\textsuperscript{c}, Robert Duller\textsuperscript{c}, Peter L.
Osterloff\textsuperscript{d} and Francisca E.
Oboh-Ikuenobe\textsuperscript{b}

\textsuperscript{a}Department of Environmental and Agricultural
Sciences, Lincoln University, Jefferson City, MO65101, USA

\textsuperscript{b}Department of Geosciences and Geological and
Petroleum Engineering, Missouri University of Science and Technology,
Rolla, MO 65409, USA

\textsuperscript{c}School of Environmental Sciences, University of
Liverpool, Liverpool, L69 7ZT, UK

\textsuperscript{d} Exploration and Production, Shell International,
London, E14 5NR, UK

Corresponding author: adojoh@ Lincolnu.edu; adojoho@mst.edu

\textbf{Abstract}

This paper examines the impact of climate-sea level controls on the
vegetation and evolution of the Niger Delta during the Late Quaternary.
The extraneous controls on the environment outlined in this context
confirm a direct link between vegetation dynamics (pollen data),
sediment supply, and the landscape evolution of the Niger Delta between
20 ka and 6.5 ka. Two phases of sedimentation are recognised based on
multiple proxies analysed in three gravity cores obtained from the
shallow offshore at \textasciitilde{}40 m water depth. Phase I records
abundant occurrences of Poaceae, Cyperaceae, and \emph{Podocarpus}pollen
from a dry hinterland, charred grass cuticles, nonmarine
alga\emph{Pediastrum} , high Ti/Zr ratio, and lower sedimentation from
20-11.7 ka. Phase II records an expansion of mangrove vegetation, high
Fe/S ratio, and increase in planktonic foraminifera between 11.7 ka and
6.5 ka. This second phase is attributed to sea level rise and higher
sedimentation during the development of delta plain and mangrove
vegetation on the gently sloping shelf. These sequential records provide
a new clue about the link between the evolutionary stages of the Niger
Delta landscape and vegetation dynamics during two distinct time bound
intervals, which potentially delineate the boundary between two Marine
Isotope Stages: MIS2 (late glacial period) and MIS1 (interglacial
period).

\textbf{Keyword} : Mangrove pollen, biogeochemistry, Niger Delta,
landscape evolution, sea level- climate change, Late Quaternary

\textbf{Introduction}

The reconstruction of the vegetation dynamics and deltaic shift of the
Niger Delta during the late to post-glacial period (Marine Isotope
Stages MIS1 and MIS2) over the last 20 ka has been the subject of debate
(2009; Adojoh et al., 2017; Adeonipekun and Sowunmi, 2019). This study
presents a model that explains the interplay between the driving
mechanisms and palaeoenvironmental settings in the basin based on biotic
and abiotic evidence (Zong et al., 2009; Adojoh et al., 2017; Boyden et
al., 2021). Previous studies of the Late Quaternary sea level in the
shallow offshore of the Niger Delta and other West African regions
indicate post-glacial sea level rise (SLR) and a middle Holocene SLR,
followed by a subsequent fall to the present time (e.g., L\selectlanguage{ngerman}ézine, 1997;
Lézine et al., 2005; Scourse et al., 2005; Miller and Gosling, 2013;
Bouimetarhan et al., 2015; Joo-Chang et al., 2015; Chadwick et al.,
2020). Climate-driven sea level change and local fluvial sediment
discharge are among the factors controlling evolution of the Niger Delta
during the Quaternary (Lézine, 1997; Adojoh et al., 2017; Adeonipekun
and Sowunmi, 2019). Several shallow offshore palaeoenvironments exist in
this setting, such as the littoral realm (mangrove swamps, barrier
islands, lagoons, deltas), and inner neritic realm. These
palaeoenvironments may be composed of an integrated depositional system,
and thus cannot be examined in sequestration (Woodroffe, 2002, Cohen et
al. 2014). The major depositional systems under rising sea level on a
gently sloping sandy coast are barrier islands or littoral system, while
strand-plains (sand belt) with beach-ridges are essentially absent
(Cohen et al., 2014, Chadwick et al., 2020).

The response of the shallow offshore paleoenvironments of the Niger
Delta to sea level changes is influenced by tidal impact, and climate
driven-nearshore wave and fluvial discharge relative to the nature of
the sedimentary budget (Lézine et al., 2005; Adojoh et al., 2017). All
littoral settings assumed their present structure during the sea level
transgression that occurred during the Last Glacial Maximum (LGM), about
20-25 ka (Poumot 1989; Lézine, 1997; Riboulot et al., 2012; Cohen et
al., 2014 Adojoh et al., 2017; Chadwick et al., 2020). Nevertheless, a
sea level fall promotes extremely adverse conditions for the origination
and preservation of the littoral and neritic realms, especially in
wave-controlled settings of the delta. Thus, if rapid fluvial/sediment
supply occurs during shoreline progradation, it may generate a delta
(Cohen et al., 2014, Chadwick et al., 2020). Under this circumstance and
depositional complexities, lagoons, shoreface and the neritic realm
evolve, and wave-dominated deposits may rapidly prograde, causing
regressive sand strands (Martin and Suguio, 1992; Chadwick et al.,
2020).

Some major questions associated with this complexity remain unanswered
in relation to the link between the nature of the vegetation dynamics
and timing of sediment supply to the onshore and shallow offshore Niger
Delta areas, as well as the impact of the Niger and Benue Rivers and
their tributaries (Adojoh et al., 2017) (Figure 1). The significance of
the key vegetation distribution over the post glacial evolution of the
Niger Delta is still not well known, in particular how the mangrove
ecosystem has responded to sea level changes and the impact of Holocene
warm and wet conditions on the coastal vegetation. This study attempts
to answer some of these questions through the evaluation of
palaeovegetation dynamics and sediment supply using three gravity cores
(GCs) (Figure 1). When present, mangrove vegetation and marine sediments
along the littoral realm can be used as markers of coastal and delta
dynamics, since their locations within the intertidal zone are strongly
influenced by SLR (Woodroffe,1989, 1995, 2002; Lézine, 1997; Scourse et
al., 2005; Adojoh et al., 2017; Adeonipekun and and Sowunmi, 2019). The
mangroves and littoral fringe of most tropical settings have kept up
with sedimentation and can accommodate eustatic SLR rates of
\textasciitilde{} 3.8 mm/year. However, when eustatic rates surpass 5.2
mm/year, then the mangroves would not be preserved (Mckee et al., 2007;
Cohen et al., 2014; Chadwick et al., 2020).

The main aim of this study is to establish the relationship between the
evolution of the Niger Delta landscape and vegetation dynamics during
the Late Quaternary. In addition, it explores the significance of
detailed and integrated multiproxy data (key pollen indicators,
biogeochemistry, planktonic foraminifera and sedimentology) to identify
the main controls on the distinct stages of the Niger Delta evolution
and its reorganisation during the Late Quaternary (MIS1 and MIS2). The
methodological approaches will contribute to the body of knowledge on
the factors affecting the depositional succession (stages of evolution)
of the West African region through the impact of climate-driven sea
level fluctuations on the coastal/littoral vegetation and delta
dynamics.

\textbf{2. Niger Delta setting}

The Niger Delta is situated in the Gulf of Guinea on the passive
Atlantic margin of West Africa and consists of a tripartite sedimentary
sequence (Figure 2). During the Palaeogene and Neogene, it built out
onto the Atlantic Ocean at the mouth of the Niger-Benue River system, a
catchment area that encompasses more than one million square kilometres
of predominantly savannah-covered lowlands (Morley, 1995; Adeonikpekun
and Sowunmi, 2019). A recent comprehensive analysis by George et al.
(2019) indicates that the extent of the Niger Delta is
70,000\selectlanguage{english} km\textsuperscript{2}, contrary to earlier publications that
documented 75,000\selectlanguage{english} km\textsuperscript{2} (Figure 2). The delta has also
been remapped and classified into mega- sedimentary environments as
follows: upper deltaic plain, lower deltaic plain, and delta front
comprising 69\%, 25\%, and 6\% of the total extent, respectively (Doust
and Omatsola, 1990; Omuije et al., 2015; George et al., 2019). The
regressive wedge of clastic sediments which comprises the delta is
estimated to reach a maximum thickness of about 12 km (Okpoli and
Arogunyo, 2020).

The palaeoenvironmental and sedimentological evolution of the Niger
Delta has experienced dramatic changes over the Quaternary period (Doust
and Omatsola, 1990; Reijers, 2011). The accumulation of marine sediments
in the rifted basin undoubtedly commenced during the Early Cretaceous
period (Albian time), following the opening of the South Atlantic Ocean
as a result of rifting between the African and South American plates
(Bonne, 2014; George et al., 2019). However, the current delta
development only began in the late Palaeocene-Eocene when sediments
began to bulge outside the syncline between the basement horst blocks at
the northern flank of the recent delta setting (Figure 2). Since then,
the delta plain has advanced southward onto the oceanic crust, possibly
assuming a lobate morphology across the shallow offshore shoreline
(Reijers, 2011). The proprietary concern of the petroleum companies
prospecting in the basin and lack of published data have complicated the
interpretations about the evolution of the delta for a long time.

The Niger Delta is normally categorised as tidally and wave-influenced
in the classic terminology of Galloway (1975). The Cenozoic
stratigraphic sequence comprises clastic sediments (Agbada and Benin
formations) advancing over ductile marine shales (Akata Formation)
(George et al., 2019; Figure 2). Previous studies indicate that the
sedimentation pattern is composed of five depobelts (Figure 1)
controlled by gravity-driven tectonism due to the presence of a mobile
ductile shale at the base of the sediment fill (e.g., Corredor et al.,
2005; George et al., 2019). The deltaic configuration has experienced
broad progradation (circa 300 km) since the Palaeocene, with a maximum
sediment thickness of approximately 12 km, and a surface area of 140,000
km\textsuperscript{2} (Doust and Omatsola, 1990; Stacher, 1995; Reijers,
2011; George et al., 2019; Figure 2). In addition, past investigations
of marine core sediments obtained from the Niger Delta suggest that
changes in the riverine input during the Late Quaternary were linked to
global glacial-interglacial cycles (e.g., Riboulot et al., 2012; Adojoh
et al., 2017, 2019; Adeonikpekun and Sowunmi, 2019). Periods of warm
temperature over Greenland were found to be associated with enhanced
river discharges in West Equatorial Africa and conversely, cold
conditions were related to weak river input (Shannahan et al., 2007;
Weldeab et al., 2007; Miller and Gosling, 2013; Adojoh et al., 2017,
Adeonikpekun and Sowunmi, 2019).

\textbf{3. Materials and methods}

The three gravity cores (GCs) utilized for this study were collected
from the Niger Delta by Fugro Geotechnical Company for Shell Petroleum
Development Company of Nigeria in 2002 (Adojoh et al., 2020; Figure 1).
The cores were acquired from the seabed within the near shore (shallow
marine) realm at approximately 40\selectlanguage{english} m water depth (Adojoh et al., 2017,
2020). They were well positioned in the eastern (GC1\selectlanguage{english} =\selectlanguage{english} Latitude -
4deg49\selectlanguage{english}"43\selectlanguage{english} N, Longitude - 5deg20\selectlanguage{english}'20\selectlanguage{english}" E), central (GC2\selectlanguage{english} =\selectlanguage{english} Latitude - 4deg05\selectlanguage{english}'08\selectlanguage{english}"
N, Longitude - 6deg33\selectlanguage{english}'30\selectlanguage{english}" E) and western (GC3\selectlanguage{english} =\selectlanguage{english} Latitude - 4deg11\selectlanguage{english}'59\selectlanguage{english}" N,
Longitude - 7deg21\selectlanguage{english}'29\selectlanguage{english}" E) parts of the delta (Figure 1; Adojoh et al.,
2017, 2020). A detailed lithological description on the scale of 1:10 cm
was undertaken to select the intervals for detailed microfossil and
biogeochemical analyses. Each gravity core was sampled at every 2 cm for
detailed stratigraphic, chronostratigraphic and palaeoenvironmental
study, and to further infer the imprints of sea level/climate cycles and
vegetation dynamics over time.

Preparations for palynomorphs, nannoplankton and foraminifera data
followed the standard procedures described in Adojoh et al. (2017,
2020). In addition, the geochemical components of the three GC samples
were analysed at 2 cm intervals for physical and chemical properties
using a Bruker S2 Ranger XRF Spectrophotometer Autosampler. In this
study, 28 samples were selected as required for the maximum batch of 28
clean and dry pots. Nylon film was used to separate the individual pots
while the bases of the pots were kept flat and level with no
protrusions. The samples were compacted gently by using the brass
plunger. All recorded measurements were obtained from the saved drive of
the XRF analyser database and used for graphical plots.

The samples for Ti/Zr and Fe/S ratios were selected in their ranges of
elemental analyses for the XRF Spectrophotometer. High Ti/Zr ratios of
hinterland pollen provide information on the extent of fluvial materials
supplied from terrestrial environments, whereas high Fe/S ratios provide
the extent of inherent marine shale deposited on the continental shelf
(Marius and Lucas, 1991; Zabel et al., 2001; Adegbie et al., 2003;
Doktorgrades, 2004; Mendoza, 2007).

Adojoh et al. (2017, 2020) based the age model for each gravity core
only on biostratigraphy defined by the first occurrences (FO) of
calcareous nannoplankton (NN19 to NN21) and planktonic foraminifera
(\emph{Glorobotalia tumida} and \emph{Glorobotalia truncatulinoides} ).
Those studies could not utilize radiometric dating because the impact of
freshwater dilution on the near-shelf margin affected the preservation
and quantitative counts of fossil materials, such as foraminiferal
tests, macrofossil shells (gastropod, bivalves), and wood particles,
that could have been used for dating. However, this present study has
compared the dated multiple proxy records from the GCs with published
data on relative sea level change for the Niger Delta region over the
last 20 ka. In Figures 3-5, we have extrapolated the relative sea level
curve for the Gulf of Guinea region plotted against the radiocarbon date
from a global isostatic model database (Peltier, 1994) and a
representative location (5830V S, 11830V E, T89-16 core) on the Congo
shelf margin (Scourse et al., 2005).

\textbf{4. Results}

The photomicrographs and microfossil taxonomical records of the three
GCs published by Adojoh et al. (2017, 2019), other non-pollen proxies,
and some selected key pollen/vegetation proxies are used to establish
the link between vegetation dynamics and landscape evolution of the
Niger Delta. The three GCs record remarkably similar changes in the
different proxies and two main phases of sedimentation were
distinguished (Figures 3-5).

\textbf{4.1 Phase I: Lower Depths (GC1: 272-202 cm, GC2: 266-202 cm,
GC3: 260-202 cm)}

The lower depths record lower sedimentation of intercalated fine to
medium sand (GC1 = 9.8cm/kyr; GC2 = 13.9cm/kyr; GC3 = 13.1 cm/kyr), high
abundances of hinterland components (e.g., \textasciitilde{}40-41\%
Savannah grass pollen -- Poaceae, 30\% Cyperaceae (Fluvial and
Freshwater indicator), 19-21\% charred grass cuticles,
\textasciitilde{}43\% afromontane taxon -- \emph{Podocarpus} ),
\textasciitilde{}18-19\% freshwater algae -- \emph{Pediastrum} , high
Ti/Zr ratio (Table 1). In addition, low abundances of planktonic
foraminifera \emph{Globorotalia}spp. (\textasciitilde{}18-20\%) and
mangrove pollen (\emph{Rhizophora}21\%, Avicenniaceae
\textasciitilde{}13\%), and low Fe/S ratio (\textasciitilde{}10-15
mg\textsuperscript{-1}/ppm) are also recorded at these depths (Figures
3-5). Thus, hinterland indicators increased relative to
mangrove/littoral proxies.

\textbf{4.2 Phase II: Mid-Upper Depths (GC1: 0-202 cm, GC2: 0-202 cm and
GC3: 0-202 cm)}

These depths cover the middle to the upper parts of the three GCs and
are characterised by a slower sedimentation rate of mudstone, expansion
of mangrove vegetation (\textasciitilde{}60-80\% \emph{Rhizophora} sp.
and 25-30\% Avicenniaceae), high Fe/S ratio (Table 1), and increase in
planktonic foraminifera (\textasciitilde{}60-79 \%
\emph{Globorotalia}spp.). These depths also record fewer hinterland
pollen (e.g., \textasciitilde{}10-20\% Poaceae, 0-5\% \emph{Podocarpus}
, \textasciitilde{}7\% Cyperaceae, 0-4\% charred grass cuticles),
2-5\%\emph{Pediastrum} , low Ti/Zr ratio, and higher sedimentation rate
of very fine-silty sand (GC1 = 78.2 cm/kyr; GC2 = 57.3 cm/kyr; GC3 =
57.3 cm/kyr) (Table 1). During this interval of rapid expansion of
mangrove-dominated pollen, hinterland pollen and other components (e.g.,
Ti/Zr, cuticles) dramatically decline when compared to the lower depths
(Figures 3-5).

\textbf{5. Discussion}

The three GCs record a coherent signal of significant changes in
geochemical ratios and abundances of palynomorphs and planktonic
foraminifera that correlate with the effects of the transition from low
sea level (phase I) to sea level rise (phase II) on the coastal margin
of the Niger Delta. This change in sea level has been reported elsewhere
especially along the West equatorial African margin (Lezine, 1997;
Scourse et al., 2005; Adeonikpekun and Sowunmi, 2019). In addition,
these phases record transitions between seasonal variations in
vegetation dynamics, sediment supply, catchment preferences, and climate
change in the Niger Delta.

\textbf{5.1 Phase I: NN19/MIS2}

This phase correlates to the later part of the last glacial period
(MIS2) which is characterised by fluvial run-off from open landscape
vegetation (Dupont and Agwu, 1991; Morley, 1995; Morley et al., 2011,
2017; Miller and Gosling, 2013; Cohen et al., 2014; Adojoh \emph{et al.}
, 2017; Adeonikpekun and Sowunmi, 2019) (Figure 7). It provides evidence
of fluvial sediment supply to the Niger Delta based on abundant records
of the hinterland indicators interpreted from the lower part of the GCs
Zabel et al., 2001; Adegbie et al., 2003; (Pastouret et al., 1978;
Morley and Richards, 1993; Skonieczny et al., 2015; Adojoh et al., 2017;
Adeonipekun and Sowunmi, 2019; Boyden et al., 2021) (Figures 3-5).
Significant records of hinterland pollen taxa in several other sediment
cores in west equatorial Africa, such as T89-16, MD03-2708, and
GeoB-4905 (Kim et al\emph{.} , 2010; Marret et al\emph{.} , 2001;
Skonieczny et al., 2015) indicate dry conditions. In addition, the
observed fluvial sediment supply could be linked to the seasonal
latitudinal migration of the Intertropical Convergent Zone (ITCZ) with a
mean annual position assumed to be around 13\textsuperscript{o}N
positioned further south (10\textsuperscript{o}S) (Leroux, 1993; Marret
et al\emph{.} , 2001; Shannahan et al., 2015; Adojoh et al., 2017;
Hopker et al., 2019; Dai et al, 2021; Boyden et al., 2021).

Assuming the sedimentation pattern remained uneroded, this phase could
be the main conduit through which terrestrial and riverine materials
were transported to the Niger Delta during the sea level fall and dry
climate (Figure 1). It was possible that sediment transport was local
(period of intense tectonism), regional (climate sea and level change),
or experienced both conditions, which contributed to the volume of
sediment discharge through the Niger and Benue Rivers to the Niger Delta
(Adegbie et al., 2003; Skonieczny et al., 2015; George et al., 2019)
(Figure 1).

\textbf{5.2 Phase II: NN20-NN21/MIS1}

Mangrove assemblages (e.g., \emph{Rhizophora} sp\emph{.} ) can be linked
to stages of sea-level and climate change over the last 20 ka (Lezine,
1997; Scourse et al., 2005; Punwong et al., 2013; Adojoh et al., 2017;
Morley, 2017), as also inferred in this study (Figures 6-7). During the
Early to mid-Holocene (11-6.5 ka), this phase experienced sea level
transgression and warm climate based on the higher sedimentation rate,
expansion of mangrove vegetation, and marine indicators in the GC depths
of \textasciitilde{}202-0 cm (Figures 3-5). This was a setting of both
rapid spread of the coastal/littoral vegetation zone associated with sea
level rise and linked to the gently sloping shelf where transgressive
sedimentation took place, leading to delta plain retreat (Morley, 1995;
Rull, 2002; Torricelli et al., 2006; Amorosi et al., 2014; Adojoh et
al\emph{.} , 2015, 2017; Adeonikpekun and Sowunmi, 2019; Hopker et al.,
2019: Dai et al, 2021). This phase also experienced increased marine
(tidal) influence when compared to phase I (GC depths of
\textasciitilde{}272-202) (Figures 3-5), implying that mangrove pollen
abundance in intertidal and tidal settings would be much higher
(Oomkens, 1974; Poumot, 1989; Morley, 1995; Rull 2002; Punwong et
al\emph{.} , 2013; Joo-Chang et al., 2015; Hopker et al., 2019) (Figures
6-7). Consequently, abundance of mangrove pollen type (\emph{Rhizophora}
) is acknowledged as an indicator of sea level transgression when
correlated with the regional sea level curve (e.g., Peltier, 1994;
Scourse et al\emph{.} , 2005; Joo-Chang et al., 2015; Adojoh et al.,
2017; Chadwick et al., 2020; Boyden et al., 2021) (Figures 3-5).

\textbf{5.3 Palaeoenvironmental evolution, climate and sea level change
implications}

The integrated multi-proxies obtained in this study provides a link to
two evolutionary time-bound stages of vegetation dynamics and sediment
supply in the Niger Delta during the last 20 ka. These two succinct
time-bound stages provide a resonating clue on the prevailing past
environment, climate and sea level change as follows: stage 1 (advancing
or prograding delta) and stage 2 (retreating or retrograding delta)
(Figures 6-7)

During stage 1, the GC data confirm the emergence of the continental
shelf in response to a lower than present day sea level (Figures 6-7).
The littoral environment (mangrove and coastal swamp) is subaerially
exposed, and sedimentation and fluvial transport are effected by mass
movement triggered by the weak West African Monsoon (WAM) (Morley, 1995;
Reijers, 2011; Zong et al\emph{.} , 2009; Shannahan et al., 2015;
Skonieczny et al., 2015; Adojoh et al., 2017; Hopker et al., 2019;
Chadwick et al., 2020; Dai et al, 2021). The GC records indicate the
predominance of hinterland pollen during stage 1 evolution of the Late
Quaternary Niger Delta. The pollen types identified were transported
beyond the littoral realm/coastal zone, representing a strong signal of
the prevalent arid conditions and low sedimentation rates (Figures 3-5;
6-7). In addition, the dominance of hinterland pollen taxa and low
abundance of planktonic foraminifera suggest that stage 1 was a distal
offshore/lower shoreface prodelta environment (Adegoke, 1975; Murray,
1991; Morley, 1995) (Figure 7). On a regional scale, this stage was a
period of an enhanced sediment transport, as observed in the settings of
the Amazon, Senegal (Ogolian regression), and Congo Rivers (Figures 3-5;
7) (Barusseau, 1988; Barusseau et al\emph{.} , 1995; Marret et al.,
2001; Giosan et al., 2005; Bonne, 2014; Adeonipkekun and Sowunmi, 2019:
Boyden et al., 2021).

Following stage 1 was a period of rapid sediment retreat in the Niger
Delta attributed to sea level rise (Figures 6-7). This period of an
onset of Early to mid-Holocene sea level rise coincides with an episode
of shoreline transgression and fine-grained sediment suspension
reflecting the proximity of turbidity currents (Peltier, 1994; Goodbred
, 2003; Scourse et al., 2005; Joo-Chang et al ; 2015; Hopker et al.,
2019; Dai et al, 2021). Increases in the values of mangrove pollen
(e.g., \emph{Rhizophora} ) and the Fe/S elemental data suggest a
reducing environment with the potential of rapid post-dissolution of
pyrite (FeS) minerals and organic-rich sulphur content during the warm
climate (Fletcher, 2005; Mendoza, 2007) (Figures 3-5; 6-7). In addition,
this stage suggests a proximal-upper shoreface (delta plain/delta front)
palaeoenvironment based on the dominance of the planktonic foraminiferal
(\emph{Globorotalia} spp.) (Figure 7). Sediment supply and pollen
deposition during stage 2 was principally driven by the interaction
between the creation of accommodation space and density of mangrove
vegetation spread across the near shore (Bonne, 2014) (Figures 6-7). On
a regional extent, stage 2 correlates to the period of sea level rise
(Nouakchottian transgression) as observed from the coastal margins of
Congo, Senegal, and Mauritania (Barusseau, 1988; Barusseau et al\emph{.}
, 1995; Lezine 1997; Lezine and Denefle, 1997; Dalibard et al., 2014;
Scourse et al., 2005; Hopker et al., 2019; Dai et al, 2021).

\textbf{6. Conclusions}

Integration of the multiple datasets in the three GCs permitted the
identification of the direct link between delta landscape and vegetation
dynamics in the eastern (GC1), central (GC2), and western (GC3) parts of
the Late Quaternary Niger Delta. The study clearly identified two
time-bound stages (1 and 2) of delta evolution as inputs for
interpreting seasonal variations in climate and sea level change. The
major findings are as follow:

\begin{enumerate}
\tightlist
\item
  Stage 1 linked the period from 20-11.7 ka to higher influx of
  hinterland pollen, slow sedimentation on the prodelta, sea level fall.
  and drier climate in the Niger Delta.
\item
  Stage 2 (11.7-6.5 ka) indicated a phase of expansion of the littoral
  realm/mangrove vegetation, higher sedimentation rate on the delta
  front, sea level rise, and warm climate.
\item
  The changes in the geochemical ratios during the two phases of
  sedimentation provided the first clarification on the timing between
  seasonal variation in vegetation, sediment supply, and
  palaeoenvironmental settings (lower / upper shoreface) in the Niger
  Delta.
\item
  Sea level change was apparently the major driver in the evolution of
  the Niger Delta based on the dominance of \emph{Rhizophora} pollen
  recorded from the GCs during stage 2.
\item
  The integrated datasets (e.g., mangrove and hinterland pollen,
  planktonic foraminifera, trace elemental ratios) provided a robust and
  coherent information for delineating the MIS2 (late glacial) and MIS1
  (interglacial) boundary.
\end{enumerate}

\textbf{Acknowledgements}

We sincerely appreciate the Petroleum Technology Development Fund of
Nigeria (PTDF Grant ID: PTDF/E/OSS/PHDAOC/385/11), and the University of
Liverpool, UK, and Missouri University of Science and Technology, USA
for funding the first author's doctoral studies and post-doctoral
research fellowship, respectively. Professor Malcolm Hart (Plymouth
University, UK) and Shell Petroleum Development Company are thanked for
their help in terms of logical suggestions and the provision of the
Gravity Cores samples, respectively.

\textbf{References}

Abbink, O.A., 1998. Palynological investigations in the Jurassic of the
North Sea region. LPP Contribution Series 8: 192.

Abbink, O.A., Van Konijnenburg-Van Cittert, J. H. A., and Visscher, H.,
2004. A Sporomorph Ecogroup Model for the Northwest European Jurassic -
Lower Cretaeous I - Concepts and framework. Netherlands Journal of
Geociences / Geologie en Mijnbouw 83, 1: 389--404

Adegbie, A.T., Schneider, R., Rohl, U. and Wefer, G., 2003. Glacial
millennial-scale fluctuation in central African precipitation recorded
in terrigenous sediment supply and freshwater signals offshore Cameroon.
Palaeogeography, Palaeoclimatology, Palaeoecology, 197, 323-333.

Adegoke, O.S., 1975. Foraminifera fauna of the polyhaline lagoons of the
Gulf of Guinea. Journal Mining and Geology, 12, 1-8.

Adeonipekun, P.A., and Sowunmi, M.A., 2019. Palaeoclimatology and
biostratigraphic significance of late Neogene/Quaternary vegetational
changes recorded in the offshore western Niger Delta. Acta
Palaeobotanica, 59, 373-390.

Adojoh, O., Dada, S., 2015. Geomorphic resources and tourism potentials
of the Niger-Benue confluence area, Central Nigeria. Journal of
Geosciences and Geomatics, 3, 44-49.

Adojoh, O., Adebayo, L.F. and Dada, S., 2015. Palynocycles,
palaeoecology and systems tracts concepts: A Case Study from the Miocene
Okan-1 Well, Niger Delta Basin, Nigeria. Applied Ecology and
Environmental Sciences, 3, 66-74.

Adojoh O., Marret, F., Duller, R. and Osterloff, P., 2017. Tropical
palaeovegetation dynamics, environmental and climate change impact from
the low latitude Coastal Offshore Margin, Niger Delta, Gulf of Guinea.
Palaeoecology of Africa, 34, 107-144.

Adojoh, O., Fabienne, M., Duller, R., Osterloff. P., 2019. Taxonomy and
phytoecology of palynomorphs and non-pollen palynomorphs: a refined
compendium from the West Africa Margin. International Journal of
Biodiversity, 3,188-200.

Adojoh O., Marret, F., Duller, R., Osterloff, P., Ikuenobe, F., Hart, M.
Smart, C., 2020. The biostratigraphy of the offshore Niger delta during
the Late Quaternary: Complexities and progress of dating techniques.
Quaternary Science Advances, 1, 100003.

Amorosi, A., Rossi, V., Scarponi, D., Vaiani, S.C. and Ghosh, A., 2014.
Biosedimentary record of postglacial coastal dynamics: high-resolution
sequence stratigraphy from the northern Tuscan coast, Italy. Boreas, 43,
939-954.

Armentrout, J.M., Fearn, L.B., Rodgers, K., Root, S., Lyle, W.D.,
Herrick, D.C., Bloch, R.B., Snedden, J.W. and Nwankwo, B., 1999.
High-resolution sequence biostratigraphy of a lowstand prograding
deltaic wedge: Oso field (Late Miocene), Nigeria. In: Jones, R.W. and
Simmons, M.D. (eds.) Biostratigraphy in production and development
geology. Geological Society, London, Special Publications, 152, 259-290.

Bankole, I., Schrank, E. and Osterloff, P., 2014. Palynostratigraphy,
palaeoclimates and palaeodepositional environments of the Miocene aged
Agbada Formation in the Niger Delta, Nigeria. Journal of African Earth
Sciences, 95, 41-62.

Barusseau, J.P., Ba-diar, A.M., deScamps, C., Diop, H. S., Giresse, P.
and Saos J.l., 1995. Coastal evolution in Senegal and Mauritania at 103,
102 and 101-year scales: natural and human records. Quaternary
International, 29, 61-73.

Barusseau, J.P., Giresse, P., Faure, H., Lezine, A.M. and Masse, J.P.,
1988. Marine sedimentary environments on some parts of the tropical and
equatorial margins of Africa during the Late Quaternary. Continental
Shelf Research, 8, 1-21.

Bonne, P.M., 2014. Cenozoic Atlantic margin of Africa during the
Cretaceous and the implications for sediment supply to the Equatorial
Reconstruction of the evolution of the Niger River. Geological Society,
London, Special Publications, 386.

Bouimetarhan, I., Dupont, L., Kuhlmann, H., Patzold, J., Prange, M.,
Schefuss, E. and Zonneveld, K., 2015. Northern Hemisphere control of
deglacial vegetation changes in the Rufiji uplands, Tanzania. Climate of
the Past, 11, 751-764.

Boyden, P., Weil-Accardo, J., Deschamps, P., Oppo, D., and Rovere, A.,
2021. Last interglacial sea-level proxies in East Africa and the Western
Indian Ocean, Earth Syst. Sci. Data, 13, 1633-1651.

Chadwick, J.A., Lamb, P.M., Ganti V., 2020. Accelerated river avulsion
frequency on lowland deltas due to sea-level rise. Proceedings of
National Academy of Sciences in the USA, 3017584-17590.

Cohen, L.C.M., Franca, M.C., Rossetti, F.D., Pessenda, R.C.L., Giannini,
F.C.P., Lorente, F.L., Buso-Junior, A.A., Castro, D., and Macario, K.,
2014. Landscape evolution during the Late Quaternary at the Doce River
mouth, Espirito Santo State, Southeastern Brazil. Palaeogeography,
Palaeoclimatology, Palaeoecology, 415, 48-58.

Corredor, F., Shaw, J.H., Bilotti, F., 2005. Structural styles in the
deep-water fold and

thrust belts of the Niger Delta. AAPG Bulletin 89, 753-780.

Dai, L., Li, S., Yu, J., Wang, J., Peng, B., Wu, B., Lao, J., Zhang, Q.,
Hao, Q., 2021. Palynological evidence indicates the paleoclimate
evolution in southeast China since late marine isotope stage 5.
Quaternary Science Reviews, 266, 106964.

Dalibard, M., Popescua, S., Maley, J., Francois Baudin, F.,
Melinte-Dobrinescue, M., Pittetf, B., Marsset, T., Dennieloug, B., Droz,
L. and Succ, J., 2014. High-resolution vegetation history of West Africa
during the last 145 ka Geobios, 46, 183-198.

Doktorgrades, E., 2004. Reconstruction of the sedimentary environment
and climate conditions by multi-geochemical investigations of Late
Palaeozoic glacial to postglacial sedimentary sequences from
SW-Gondwana. Dissertation submitted to Universitat Bonn, Germany, 96 -
117.

Doust, H.E. and Omatsola, E.M., 1990. Niger Delta. In: Edwards J.D., and
Santagrossi, P.A (eds.). Divergent/Passive Basins. American Association
of Petroleum Geologists Memoir, 48, 201-238.

Dupont, L.M. and Agwu, C.O., 1991. Environmental control of pollen grain
distribution patterns in the Gulf of Guinea and offshore NW-Africa.
International Journal of Earth Sciences, 80, 567-589.

Fletcher, W.J., 2005. Holocene Landscape History of Southern
Portugal\emph{.} Doctoral thesis, University of Cambridge;
https://doi.org/10.17863/CAM.20470.

Fredoux, A. and Tastet, J.P., 1976. Analyse pollinique d'une carotte
marine au large de la Cote d'Ivoire. Variations de la vegetation et du
climat depuis 225 000 ans BP. Palynosciences, 2, 173-188.

Galloway, W.E., 1975. Process framework for describing the morphologic
and stratigraphic evolution of deltaic depositional systems. In:
Broussard, M.L. (Ed.), Houston Geological Society, Deltas, 87-98.

George, D.C., Franklin, I.M., and Spagnolo, M.M., 2019. Deltaic
sedimentary environments in the Niger Delta, Nigeria. Journal of African
Earth Sciences 160, 103592.

Giosan, L., Donnelly, J.P., Vespremeanu, E. and Buonaiuto, F.S., 2005.
River delta morphodynamics: Examples from the Danube delta, In: Giosan,
L., and Bhattacharya, J. (eds.), River Deltas: Concepts, Models,
Examples, SEPM Special Publication 83, 393-411.

Goodbred, S.L., 2003. The response of the Ganges dispersal system to
climate change: a source-to-sink view since the last interstade.
Sedimentary Geology, 162, 83-104.

Hopker, S.N., Wu, H.C., Muller, P., Barusseau, J.P., Vernet, R.,
Lucassen, F., Kasemann. S.A., and Westphal, H., 2019. Pronounced
Northwest African monsoon discharge during the Mid-to Late Holocene.
Frontiers in Earth Science, 7, 314.

Joo-Chang, J.C., Islebe, G.A., and Torrescano-Valle, N., 2015. Mangrove
history during middle- and late-Holocene in Pacific south-eastern
Mexico. Holocene 25, 651-662.

Kim, S.Y., Scourse, J.D., Marret, F. and Lim, D.I., 2010. A 26,000-year
integrated record of marine and terrestrial environmental change off
Gabon, west equatorial Africa. Palaeogeography, Palaeoclimatology,
Palaeoecology, 297, 428-438.

Knox, G.J. and Omatsola, E.M., 1990. Development of the Cenozoic Niger
Delta in terms of the escalator regression model and impact on
hydrocarbon distribution. In: van der Linden, W.J.M., Cloetingh,
S.A.P.L., Kaasschieter, J.P.K., van der Graff, W.J.E., Vandenberghe, J.,
and van der Gun, J.A.M. (eds.), KNGMG Symposium on coastal lowland
geology and geotechnology, proceedings. The Netherlands, Kluwer Academic
Publishers, 181-202.

Knox, G.J. and Omatsola, M.E., 1987. Development of the Cenozoic Niger
Delta in terms of the escalator regression model. Kluwer Academic
Publishers, 181-202.

Leroux, M., 1993. The mobile polar high: A new concept explaining
present mechanisms of meridional airmass and energy exchanges and global
propagation of palaeoclimatic changes. Global and Planetary Change, 7,
69-93.

Lezine, A.M., Cazet, J.P. and Duplessy, J.C., 2005. West African monsoon
variability during the last deglaciation and the Holocene: Evidence from
freshwater algae, pollen and isotope data from core KW31, Gulf of
Guinea. Palaeogeography Palaeoclimatology, Palaeoecology, 219, 225-237.

Lezine, A.M, 1997. Evolution of the West African mangrove during the
Late Quaternary. Geographie Physique et and Quaternaire, 51, 405-414.

Lezine, A.M. and Denefle, M., 1997. Enhanced anticyclonic circulation in
the eastern North Atlantic during cold intervals of the last
deglaciation inferred from deep-sea pollen records. Geology, 25,
119-122.

Martin, L., Suguio, K., 1992. Variation of coastal dynamics during the
last 7000 years recorded in beach-ridge plains associated with river
mouths: example from the central

Brazilian coast. Palaeogeography, Palaeoclimatology, Palaeoecology, 99,
119-140.

Marius, C. and Lucas, J., 1991. Holocene mangrove swamps of West Africa
sedimentology and soils. Journal of African Earth Sciences, 12, 41-54.

Marret, F., Scourse, J., Versteegh, G., Jansen, J., Fred, S., and Ralph,
R., 2001. Integrated marine and terrestrial evidence for abrupt Congo
River palaeodischarge fluctuations during the last deglaciation. Journal
of Quaternary Science, 16, 761-766.

Mendoza, U.M., 2007. Dynamics of phosphorus and sulphur in a mangrove
forest in Braganca, North Brazil. PhD thesis, University of Bremen 1-16.

Miller, C.S., and Gosling, W.D., 2013. Quaternary forest associations in
lowland tropical West Africa. Quaternary Science Reviews, 84, 7-25.

McKee, K.L., Cahoon, D.R., and Feller, I.C., 2007. Caribbean mangroves
adjust to rising sea level through biotic controls on change in soil
elevation. Global Ecological Biogeography, 16, 545--556.

Morley, R.J., 1995. Biostratigraphic characterisation of systems tracts
in Tertiary sedimentary basins. Proceedings of International Symposium
on Sequence Stratigraphic in SE Asia, 50-71.

Morley, R.J., 2014. Rifting and mountain building across Sundaland, a
palynological and sequence biostratigraphy perspective. Proceedings,
Indonesian Petroleum Association Thirty-Eighth Annual Convention and
Exhibition, IPA 14-G-011M.

Morley, R.J., 2017. The complex history of mountain building and the
establishment of mountain floras in Southeast Asia and Eastern
Indonesia. In: Hoorn, C., and Antonelli, A. (eds.), Mountain, climate
and diversity. Wiley, 475-494.

Morley, R.J. and Richards, K., 1993. Gramineae cuticles: A key indicator
of Late Cenozoic climatic change in the Niger Delta. Review of
Palaeobotany and Palynology, 77, 119-127.

Morley, R.J., Swiecicki, T. and Thi-Pham, D., 2011. A sequence
stratigraphic framework for the Sunda region, based on integration of
biostratigraphic, lithological and seismic data from Nam Con Son Basin,
Vietnam. Proceedings, Indonesian Petroleum Association 35th Annual
Convention and Exhibition, IPA11-G-002.

Murray J.W., 1991. Ecology and palaeoecology of benthic foraminifera.
Amsterdam, Elsevier. 397.

Omuije, J. Ozumba, B. Adojoh, O. 2015. Depositional Controls on Niger
Delta Onshore Reservoirs. Conference Proceedings on the Sedimentology of
Paralic Reservoirs: Recent Advances and their Applications. Geological
Society, London.

Oomkens, E., 1974. Lithofacies relations in Late Quaternary Niger delta
complex. Sedimentology, 21,195-222.

Okpoli, C.C., and Arogunyo, D.I., 2020. Integration of Well logs and
seismic attribute analysis in reservoir identification on PGS field
onshore Niger Delta, Nigeria. Pakistan Journal of Geology, 4, 12-22.

Pastouret, L., Chamley, H., Delibrias, G., Duplessy, J.C., Thiede, J.,
1978. Late Quaternary climatic changes in Western Tropical Africa
deduced from deep-sea sedimentation off the Niger delta. Oceanologica
Acta 1, 217-232.

Poumot, C., 1989. Palynological evidence for eustatic events in the
tropical Neogene. Centres for Research Exploration Production Elf
Aquitaine, 13, 437-453.

Punwong, P., Marchant, R., and Selby, K.A., 2013. Holocene mangrove
dynamics from Unguja Ukuu, Zanzibar. Quaternary International, 298,
4-19.

Reijers, T.J.A., 2011. Stratigraphy and sedimentology of the Niger
Delta. Geologos, 17, 133-162.

Riboulot, V., Cattaneo, A., Berne, S., Schneider, R., Voisset, M.,
Imbert, P., and Grimaud, P., 2012. Geometry and chronology of Late
Quaternary depositional sequences in the Eastern Niger Submarine Delta.
Marine Geology, 319-322, 1-20.

Rull, V., 2002. High impact palynology in petroleum geology.
Applications from Venezuela (northern South America). American
Association of Petroleum Geologists Bulletin, 86, 279-300.

Scourse, J., Marret, F., Versteegh, G.J.M., Jansen, J.H.F., Schefuss,
E., and van der Plicht, J., 2005. High resolution last deglaciation
record from the Congo fan reveals significance of mangrove pollen and
biomarkers as indicators of shelf transgression. Quaternary Research,
64, 57-69.

Shannahan, T.M., Overpeck, J.T., Sharp, W.E., Scholz, C.A. and Arko,
J.A., 2007. Simulating the response of a closed-basin lake to recent
climate changes in tropical West Africa (Lake Bosumtwi, Ghana).
Hydrological Processes, 21, 1678-1691.

Street-Perrott, F.A. and Roberts N., 1983. Fluctuations in closed-basin
lakes as an indicator of past atmospheric circulation patterns. In:
Perrott F.A. et al. (eds), Variations in the Global Water Budget.
Street- Reidel, Dordrecht, 331-345.

Skonieczny, C., Paillou, P., Bory, A., Bayon, G., Biscara, L., Crosta,
X., Eynaud, F., Malaize, B., Revel, M., Aleman, N., Barusseau, J.,
Vernet, R., Lopez, S. and Grousset, F., 2015. African humid periods
triggered the reactivation of a large river system in Western Sahara.
Nature Communications, 6, 8751.

Stacher, P., 1995. Present understanding of the Niger Delta hydrocarbon
habitat. In: Oti, M.N., and Postma, G. (eds.), Geology of Deltas.
Rotterdam, A.A. Balkema, 257-267.

Torricelli, S., Knezaurek, G. and Biffi, U., 2006. Sequence
biostratigraphy and paleoenvironmental reconstruction in the Early
Eocene Figols Group of the Tremp--Graus Basin (south-central Pyrenees,
Spain). Palaeogeography, Palaeoclimatology, Palaeoecology, 232, 1-35.

Weldeab, S., Lea, D.W., Schneider, R.R. and Andersen, N., 2007. 155,000
years of West African Monsoon and ocean thermal evolution. Science, 316,
1303-1307.

Woodroffe, C.D., 1995. Response of tide-dominated mangrove shorelines in
northern Australia to anticipated sea-level rise. Earth Surface
Processes and Landforms, 20, 65--85.

Woodroffe, C.D., 2002. Coasts: Form, Process and Evolution. Cambridge
University Press, Cambridge, 623.

Woodroffe, C.D., Chappell, J.M.A., Thomas, B.G., Wallensky, E., 1989.
Depositional model of a macrotidal estuary and flood plain, South
Alligator River, Northern Australia. Sedimentology, 36, 737-756.

Zabel, M., Schneider, R.R., Wagner, T., Adegbie, A.T., de Vries, U. and
Kolonic, S., 2001. Late Quaternary climate changes in Central Africa as
inferred from terrigenous input to the Niger Fan. Quaternary Research,
56, 207-217.

Zong, Y., Huang, G., Switzer, A., Yu, F. and Yim, W., 2009. An
evolutionary model for the Holocene formation of the Pearl River delta,
China. The Holocene, 19, 129-142.\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image1/image1}

\end{center}
\end{figure}

Figure 1. Map of the Niger Delta showing its location in southern
Nigeria (inset) and the locations of the gravity cores (GCs). Note - The
major river was formed from the confluence of Niger (North-West Nigeria)
and Benue (South-West Nigeria) Rivers (modified after Adojoh et al.,
2017).\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image2/image2}

\end{center}
\end{figure}

Figure 2. The stratigraphy of the Niger Delta; FM = Formation (after
Doust and Omatsola, 1990).\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image3/image3}

\end{center}
\end{figure}\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image4/image4}

\end{center}
\end{figure}\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image5/image5}

\end{center}
\end{figure}\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image6/image6}

\end{center}
\end{figure}

Figure 6. A model of sea level change in relation to vegetation
dynamics, deltaic evolution, and sediment supply (grain size variation)
(modified after Morley, 2011 and Adojoh et al., 2015).\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image7/image7}

\end{center}
\end{figure}

Figure 7. Two stages of vegetation dynamics, sea level change, and
depositional settings observed in Figures 3-5 modified into the
landscape evolution of the Niger Delta during the Late Quaternary (last
20 ka).

Table 1: Sedimentation rate records of the GCs. Sedimentation rate (SR,
cm/kyr) is the thickness of sediment (Z, cm) that accumulates over a
specified time interval (age difference) (T, kyr). Therefore, SR = Z/T
where = Intervals between samples (cm); T= Age difference between
samples (kyr). The first two intervals (i.e, from 11.7-8.5 + 6.5) ka
were added to compute the SR result for the phase II.\selectlanguage{english}
\begin{longtable}[]{@{}llllllll@{}}
\toprule
\textbf{Gravity Core (GC)} & \textbf{Age (ka)} & \textbf{GC1} &
\textbf{SR (cm/} \textbf{kyr)} & \textbf{GC 2} & \textbf{SR SR (cm/kyr)}
& \textbf{GC3} & \textbf{SR (cm/ kyr)}\tabularnewline
\midrule
\endhead
Depth (cm) & 6.5 & 0-40 & 6.2 & 0-40 & 6.2 & 0-40 & 6.2\tabularnewline
Depth (cm) & 11.7 & 40-184 & 72.0 & 40-142 & 52.6 & 40-142 &
52.6\tabularnewline
Depth (cm) & 20 & 184-272 & 9.8 & 142-266 & 13.8 & 142-260 &
13.1\tabularnewline
\bottomrule
\end{longtable}\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/essoar/essoar}

\end{center}
\end{figure}

\selectlanguage{english}
\FloatBarrier
\end{document}

