The Lungmanis Association occurs:
in the Kinabatangan lowlands,
in the Dent Peninsula to the west of Tabin River,
with major developments at Lungmanis,
between Sungai Koyah and Sungai Tenegang Besar,
at Dagat in the Lumerau lowlands, and
in the Silabukan valley.
It occurs on very low mudstone hills and broad flats of mainly fine-textured alluvium. In the valley floors, the soils are similar to those described in the Kinabatangan Association.
It is formed on low relief comprising alluvial flats and minor hillocks with a relief amplitude which rarely exceeds 15 m and with slopes in the 0 to 15° range, the majority being less than 10°. The alluvial flats are often wide and include patches of swamp; they are subject to flooding. Valley floors long upper reaches of rivers tributary to the Kinabatangan are also included but these are less vulnerable to flooding.
Parent materials comprise mudstone and rare sandstone; they are bedded in the Lungmanis, Latangan, Lamag and Lumerau areas but elsewhere occur in slump formations. Sporadic pebble deposits on low hills a Dagat and in Koyah and Segaliud valleys suggest that some areas may well be terrace remnants. Fine textured alluvium occurs on the alluvial flats.