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 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. , 2010; Marret et al. , 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 13oN positioned further south (10oS) (Leroux, 1993; Marret et al. , 2001; Shannahan et al., 2015; Adojoh et al., 2017; Höpker 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).