Sub-surface foraminifera distribution and preservation in short core samples from the Strait of Malacca

Abstract

Abstract The Strait of Malacca—a shallow and hyposaline strait—is one of the busiest shipping routes in the world. It divides Sumatra and Peninsular Malaysia. This study assessed the sub- surface distribution of benthic foraminifera, their preservation, and their relationship with the sediment characteristics of the Strait of Malacca. One short sediment core sample was collected from the southern part of the Strait of Malacca. The core was then divided into 10 subsamples at every 2 cm interval. The samples were used for foraminifera identification and grain size and organic matter analysis. From the approximately 3000 benthic foraminifera that were selected and identified, 17 species exhibited ≥ 2% occurrence in at least one subsample along the core. Out of the 17 species identified, 4 species (Asterorotalia pulchella (57%), Cavarotalia annectens (13%), Discorbinella bertheloti (7%), and Pseudorotalia schoerteriana (6%)) exhibited an average relative abundance of >5% in all core intervals. Cluster analysis subdivided the core intervals into two groups: BF1 and BF2. Both the groups were dominated by A. pulchella. The PCA biplot indicated that BF1, which represented the upper sub-surface intervals, had relatively more agglutinated species than BF2. Despite being common in surface samples along the Strait of Malacca, species such as Textularia sp. were absent further down the core. This study indicated that in the sub-surface sediment of the Strait of Malacca, calcareous hyaline species, especially those belonging to Rotaliida, were abundant and readily preserved compared to the agglutinated or calcareous porcelaneous groups. The loss of several agglutinated groups down the cores indicated that a more discreet approach to paleoenvironmental interpretation using benthic foraminifera assemblages should be adopted in this region to avoid bias in the interpretation.