5.2 Phase II: NN20-NN21/MIS1
Mangrove assemblages (e.g., Rhizophora sp. ) can be linked
to stages of sea-level and climate change over the last 20 ka (Lézine,
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 ~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. , 2015, 2017; Adeonikpekun and Sowunmi, 2019;
Höpker et al., 2019: Dai et al,
2021). This phase also experienced increased marine (tidal) influence
when compared to phase I (GC depths of ~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. , 2013; Joo-Chang et al., 2015; Höpker et al., 2019)
(Figures 6-7). Consequently, abundance of mangrove pollen type
(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. , 2005; Joo-Chang et al., 2015;
Adojoh et al., 2017; Chadwick et al., 2020; Boyden et al., 2021)
(Figures 3-5).