The Kepayan Association occurs:
on terraces in the Sook, Penawan, Keningau and Ranau Plains,
near Sipitang,
on Pulau Labuan,
near Kota Belud,
on Pulau Balambangan,
on Pulau Jambongan,
in the Sugut estuary,
near Telupid in the Labuk and Ruku Ruku valleys,
at Sungai Manila and Sandakan Airport, and
on the south coasts of the Dent and Semporna Peninsulas.
The terraces are composed of tiered deposits of alluvium, with coarse-textured, sometimes pebbly, alluvium normally at the surface. Along the coasts, the terraces are presumed to be of marine origin. In all cases, they are flat with only minor surface dissection.
Parent materials comprise deposits of sand which are normally underlain by medium- to fine-textured alluvium at depths of 90 to 150 cm from the surface. Heath forest with stunted, often decaying, trees occurs naturally on the terraces. It passes sharply into dipterocarp forest at the terrace edges. In the Sandakan district, much of the natural vegetation has been disturbed by sand or gravel extraction, construction of the airport and by agricultural development.