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
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 ~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.