278-8 Sediment and pollen influx between Eastern and Western Tidal Flats of the Tropical Wouri Estuary in Cameroon: A Reflection of Depositional Environment and Sea-level Change

Session: Understanding Temporal Dynamics in Hydrogeochemistry and Sedimentary Processes in Estuarine Environments

Presenting Author:

Fatou Cisse

Authors:

Cisse, Fatou Penda ¹, Diop, Rahmatoulaye Thialaw², Ka, Maguette³, Omoyemi, Oluwaseun⁴, Adojoh, Onema C.⁵, Agbogun, Henry M.D⁶

(1) Geoscience, Fort Hays State University, Hays, Kansas, USA, (2) Geoscience, Fort Hays State University, Hays, Kansas, USA, (3) Geosciences, Fort Hays State University, Hays, Kansas, USA, (4) Geosciences, Fort Hays State University, Hays, Kansas, USA, (5) Natural Sciences, Geology, Northwest Missouri State University, Maryville, Missouri, USA, (6) Fort Hays State University, Hays, KS, USA; Athabasca University, Athabasca, AB, Canada,

Abstract:

The Wouri Estuary is a dynamic depositional environment shaped by the interplay of marine and fluvial processes, making it an ideal setting for studying temporal and spatial variations in sediment inputs. This study investigates differences in sediment deposition across the eastern and western flanks of the estuary through palynological analysis of two sediment cores ~87 cm and ~78 cm in length collected from tidal flats on the western and eastern margins, respectively.

Four palynological slides were prepared from each core following acid digestion processes and analyzed using a trinocular microscope to transversely identify and count pollen grains, spores, and non-pollen palynomorphs (NPPs) (freshwater algae, cuticle fragments, phytoclasts).  Our results show that the western core is characterized by the dominance of Rhizophoraceae and Euphorbiaceae pollen, and Polypodiaceae spores.  This suggests strong influence of mangrove vegetation (humid-intertidal conditions) dynamics and terrestrial runoff from the hinterland, respectively. The observed trend declines in Rhizophoraceae (Rhizophora sp.) from the base to mid-section of the core, followed by an increase toward the surface which reflects sea-level fluctuations, transitioning from highstand to lowstand and rising again in recent times.

In contrast, the eastern core is dominated by Fabaceae, Apocynaceae, Poaceae, palm pollen, freshwater algae, and grass cuticle, indicating sediment input primarily from freshwater, savanna, and riparian sources. Minimal variation in microfossil assemblages with depth suggests a relatively stable depositional environment and terrestrial transport to this part of the estuary.

By linking palynological assemblages to depositional environments, this study enhances the understanding of sediment flux and sea level dynamics in the Wouri Estuary and demonstrates the utility of palynofloral and non-pollen palynomorphs distribution in reconstructing paleoenvironmental conditions in tropical coastal systems.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-8791

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