Distribution of Foraminifera off the Terengganu River Mouth, East Coast Peninsular Malaysia

Abstract

The distributions of modern foraminiferal species represent an important tool for petroleum geologists to characterize paleoenvironments. This paper documents the distribution of benthic foraminifera on the inner shelf (<40 m water depth) immediately offshore of the Terengganu River mouth, one of the three major drainages on the east coast of peninsular Malaysia. Sediment substrate type primarily controls the distribution of species; temperature, salinity, dissolved oxygen, and pH vary little in the study area and have little influence. Sandy substrates (mostly coarse and very coarse sand) from 20 to 40 m water depth are characterized by abundant specimens of the larger foraminifera Amphistegina spp. Muddy substrates immediately adjacent to the Terengganu River mouth from 12 to 20 m water depth are characterized by higher diversity assemblages dominated by several smaller calcareous taxa and the agglutinated species Ammobaculites exiguus. The latter species has been documented in muddy sediments at other river mouths on the east coast of peninsular Malaysia. Strong, seasonally reversing monsoon-driven currents affect sediment transport along the east coast of peninsular Malaysia and therefore indirectly influence the distributions of foraminiferal species. The results of this study add to the increasingly extensive database on modern foraminiferal distributions that provides a model for paleoenvironmental interpretations of hydrocarbon-bearing Neogene strata off the east coast of Thailand and peninsular Malaysia.

Early-to-mid Holocene environmental change in the Kallang River Basin, Singapore

“…Brackish conditions likely continued until about 5.8 cal ka BP when Cluster V is replaced by Cluster VI (Figure 5.8). Cluster VI is dominated by Ammonia turgida and Cellanthus biperforatus (Table 5.3), which are usually found in lagoons and estuary mouths in slightly hyposaline conditions (e.g., Debenay and Luan, 2006;Culver et al, 2020;. Additionally, the foraminiferal tests found in Cluster VI were mostly broken and abraded (Figure 5.7), which could have been caused by higher wave energy.…”

“…Similarly, Amphistegina sp. were mostly found in sandy substrates off the Terengganu River mouth at water depth 20 -40 m Culver et al, 2020) and in the Pahang River estuary with water depth of more than 15 m (Faiz et al, 2018).…”

“…Foraminiferal tests found in the underlying Cluster VI are mostly broken (Figure 5.7), suggesting transportation or reworking of materials in a relatively high energy environment (Murray and Alve, 1999b;Francescini and Compton, 2007). High wave energy also has the potential to remobilise the sediments and hence is not conducive for some benthic foraminifera to survive (e.g., Wilson, 2006;Culver et al, 2020), thereby explaining the low diversity observed in Cluster VI. While there might be other taphonomic factors such as dissolution at play, the broken tests found in Cluster VI suggest that hydrodynamics is the likely reason for the absence of foraminifera at the top of the core.…”