Analysis on the formation of rhizolith clumps from Shidao, Xisha Islands

Rhizolith is the fossilized remain of higher plants. It can not only confirm the existence of paleosols, but also provide a lot of information for paleo-vegetation, paleoclimate and sedimentary environment. On the Shidao of Xisha Is-lands in the South China Sea, rhizoliths are widely distributed in the supratidal zone of the east and west coasts, but theyare rarely reported on the other islands in the South China Sea. Most of the rhizoliths are observed as individuals on the rock walls and in the paleosols. In addition, well-preserved rhizolith clumps are also exposed within the supratidal zone. In this study, high-resolution X-ray microtomography (Micro-CT) was used to conduct three-dimensional visualization analysis of the rhizoliths from Shidao to obtain their fine, detailed morphological characteristics. In combination with the phytoecology and microstructure characteristics of the rhizoliths, this paper discusses the formation of rhizolith clumps from Shidao, so as to provide reference information on the formation mechanism and sedimentary environment recon-struction of rhizoliths in coastal environments. The macroscopic three-dimensional morphology, obtained by high-resolution X-ray microtomography (Micro-CT), intuitively demonstrates that the internal structure of the rhizoliths can be divided into three zones. Combined with the results of thin sections, it is inferred that the inner zone and middle zone of Shidao rhizoliths are formed by the metasomatism of plants themselves, while the outer zone is formed by the consolidation of coral sand. The morphological characteristics and ecological adaptability of the vegetation indicate that the rhizolith clumps of Shidao are formed from the stems, rather than the roots. At the same time, it is preliminarily speculated that the native vegetation is Scaevola taccada, a dominant specie on Shidao.

Project Supported:

Clc Number: