Last Interglacial sea-level proxies in East Africa and the Western Indian Ocean

Abstract

Abstract. In this paper, we describe a sea-level database compiled using published Last Interglacial, Marine Isotopic Stage 5 (MIS 5), geological sea-level proxies within Eastern Africa and the Western Indian Ocean (EAWIO). Encompassing vast tropical coastlines and coralline islands, this region has many occurrences of well preserved last interglacial stratigraphies. Most notably, islands almost entirely composed by Pleistocene reefs (such as Aldabra, the Seychelles) have provided reliable paleo relative sea-level indicators and well-preserved samples for U-series chronology. Other sea-level proxies include uplifted marine terraces in the north of Somalia and tidal notches in luminescence limited aeolian deposits in Mozambique. Our database has been compiled using the World Atlas of Last Interglacial Shorelines (WALIS) interface and contains 57 sea-level indicators and 2 terrestrial limiting data points. The database is available open access at https://doi.org/10.5281/zenodo.4043366 (Version 1.02) (Boyden et al., 2020).

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

“…This phase correlates to the later part of the last glacial period (MIS2) which is characterised by fluvial runoff from open landscape vegetation (Dupont and Agwu, 1991;Morley, 1995;Morley et al, 2011Morley et al, , 2017Miller 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.…”

“…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 13 o N positioned further south (10 o S) (Leroux, 1993;Marret et al , 2001;Shannahan et al, 2015;Adojoh et al, 2017;Hopker et al, 2019;Dai et al, 2021;Boyden 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;Hopker 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).…”

“…The reconstruction of the vegetation dynamics and deltaic shift of the Niger Delta during the late to postglacial 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 postglacial sea level rise (SLR) and a middle Holocene SLR, followed by a subsequent fall to the present time (e.g., Lézine, 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).…”