L'evoluzione olocenica della Lower Central Plain di Bangkok (Tailandia) sulla base delle faune fossili a molluschi

Fossil molluscan assemblages are analyzed in order to reconstruct the evolution of the Northern Gulf of Thailand during Holocene. The marine sediments (Bangkok Clay Formation) of the Lower Central Plain of Bangkok and the coastal plain of Phetchaburi were sampled in 16 localities, obtaining fossil shells whose 14C ages range from 9000 to 2000 years BP. A statistical treatment of abundance data returned four major groups, namely the Dendostrea rosacea association (intertidal mud), the Corbula fortisulcata - Mactra luzonica association (shallow infralittoral sandy mud), the Nuculana mauritiana - Timoclea scabra association (infralittoral sand spit) and the Timoclea scabra - Arcopagia pudica association (infralittoral mud). The data allowed both a stratigraphic correlation along two transects covering all the Holocene basin and the creation of digitalized maps showing the presumable extension of the Thai paleogulf around the apex of Flandrian transgression event (about 5500 years BP).