Characteristics of Carbonate Surface Sediments in the NE Chuuk Lagoon, Micronesia: Halimeda, a Major Constituent

Abstract

The surface sediments in Chuuk lagoon are mostly composed of Halimeda segments and benthic foraminifera skeletons. The variations in grain-size distribution and mean grain size with water depth could be ascribed to relative differences in sediment supply from Halimeda and benthic foraminifera. The dense inhabitation of Halimeda in the relatively shallow waters has produced a large amount of gravel-sized sediments. In contrast, benthic foraminifera have been supplied sand-sized sediments in relatively deep waters where Halimeda population is relatively lower. Because the Chuuk Atoll is characterized by relatively a large dimension of the atoll with deep lagoon, carbonate surface sediments in the deep lagoonal area have been mostly supplied from Halimeda and benthic foraminifera rather than corals.ediment supply from Halimeda and benthic foraminifera. The dense inhabitation of Halimeda in the relatively shallow waters has produced a large amount of gravel-sized sediments. In contrast, benthic foraminifera have been supplied sand-sized sediments in relatively deep waters where Halimeda population is relatively lower. Because the Chuuk Atoll is characterized by relatively a large dimension of the atoll with deep lagoon, carbonate surface sediments in the deep lagoonal area have been mostly supplied from Halimeda and benthic foraminifera rather than corals.