Distribution of foraminifera in late quaternary sediments off High Island, Hong Kong

Abstract

The distribution of foraminifera in a borehole off High Island, Hong Kong was investigated to assist Quaternary palaeoenvironmental reconstruction. The results confirmed the existence of an upper and lower marine strata of the Holocene and the last interglacial age respectively, separated by an upper terrestrial stratum of the last glacial age. Diversity and abundance of foraminifera are greater in the upper marine stratum while foraminiferal tests in the lower marine stratum are usually reddish-brown in colour, which is explained by iron-staining during the last glacial low sea-level stand. The latter is underlain by a lower terrestrial stratum and residual soil. The presence of large foraminifera often with broken tests in the upper marine stratum is indicative of a subtropical high energy rocky shore environment during the Holocene period. Unlike previously studied sites in Hong Kong, the present borehole yielded abundant Amphistegina which reflected a sedimentary environment in close proximity to patcy coral reefs. Based on radiocarbon dates obtained elsewhere in Hong Kong, the lower marine stratum is last interstadial in age ranging from ca. 30,000–45,000 yr b.p. However, because of the high elevation of the stratum, palynological and oxygen-isotope evidence, the last interglacial age is considered to be more likely.