The Weston Association is extensive in bays and estuaries:
On the west coast, there are major developments in the Padas delta and around Marudu Bay,
On the east coast, the association is almost continuous from the Bengkoka Peninsula to the Dent Peninsula with major developments in Schomburgk Bay, Labuk Bay, Sandakan Harbour and in the deltas of the Kinabatangan and the Segama,
In the southeast, it is particularly extensive in Cowie Harbour.
The association is formed in tidal swamps with 3 distinctive landforms, namely tidal flats, ‘crab’ mounds and platforms formed of coalescent ‘crab’ mounds. Parent materials consist of mainly fine-textured sulphidic alluvium and peat. The natural vegetation comprises forests of mangroves and nipah palm (Nypa fruticans).
The natural vegetation, which covers the whole association, comprises forests of mangroves and nipah palm Nypa fruticans. Rhizophora mucronata, Rhizophora apiculata, Bruguiera parviflora and Excoelania agallacha occur in tidal flats. Somewhat drier sites on low crabs mounds support Ceriops tagal, Xylocarpus granatium and Avicenia alba with the piah fern Acrosticum aureum on the summits of the mounds.