Microfossils from the Bangkok Clay Formation (Upper Holocene) of central Thailand: Paleoenvironmental insight

Abstract

Palynomorphs and benthic foraminifers are reported from the Upper Holocene Bangkok Clay Formation at a whale-fall excavation site in Samut Sakhon Province, located 15 kilometers from the shoreline of the Gulf of Thailand. The aim of this research is to interpret the paleoenvironment of the whale-trapped layer using bioindicator assemblages. Twenty-two palynomorphs are identified. The palynomorphs are composed of tropical plants and categorized based on their ecological communities into five groups: mangrove, back mangrove, floodplain, terrestrial, and ferns. Of these, mangrove and floodplain pollen assemblages are dominant. The pollen was transported via aeolian and fluvial systems to deposit in the delta system, then wave and tide processes dispersed them to the deeper part of the sea floor. The foraminiferal assemblage is dominated by marine ammonioids and miliolids without agglutinated forms, representing a shallow marine setting with low freshwater influence. The assemblages of foraminifers together with ostracods, gastropods and diatoms suggest sedimentary deposition in shallow subtidal marine environments, where salinity varied from slightly brackish to normal. The terrigenous sediment influx was high; the depositional environment is likely to be the distal part of a prodelta.