... compositionexpressdifferent paleogeographic environments suchas marine, continental environment ortransitionalenvironment. In the Red River Delta area, the facial association rule is examined in _______ ... of fine grained size leading to the waterbearingcapacityisverylowandplays a roleasaquicludes.Besides, in thesefinegrainsizelayers, the contentsofarsenicandironarehigh,especially in darkclay,siltyclayrich in organic ... 23(2007)170‐176173tidalflatsiltysandandlagoonalclayandlensesof lacustrine clay of Ha noi Formation, the laterizedlagoonalclayofVinhPhucFormation, the alternating greenish gray clay and peatbearing swamp clayey...