Foraminiferal and thecamoebian biosedimentary facies are shown to be potentially diagnostic of specific estuarine conditions in which no macrofauna are present or of use. Agglutinated foraminifera in this setting are well adapted to low salinity, and show the largest abundance and widest redistribution of foraminiferal mangrove species, reflecting the net bedload mixture. Thecamoebians are also present in this zone. Sand percentages and microfaunal data delineate a bilobed birdfoot bay-head delta, which progrades into the central basin. Coarse sand mixed with mud may be present in scour holes of fluvial estuarine outlets.
Fine sediment is present around shoals protected by islands.
Foraminifera define a transitional biofacies in this central basin, which separates an inner domain with agglutinated species and a seaward domain with the first occurrence of calcareous species. Values of organic matter and CaCO3 are low. More diversified assemblages of calcareous foraminifera are dominant. These are adapted to the higher salinity and pH of this deeper estuarine zone. The net bedload transport is headward at the narrow inlet and contiguous areas, and seaward at the rest.