The Tengah Nipah Association occurs:
mainly in the west of the Dent Peninsula, and
in the Tengah Nipah area east of Lahad Datu.
The distinctive feature in this area, referred to as the Ganduman Hills, are the subparallel broad ridges, which are aligned from north to south and which are separated by narrow tonguing valleys. The ridges, with an amplitude of about 60 m, consist of narrow ridge crests and convex upper slopes, which become concave and level off to gently sloping flats. There may be 2 or 3 of these flats on a hillsides. Slopes range from 5-15°, but may reach 20° near the crests. To the south, where the amplitude increases to approximately 90 m, slopes are rather steeper and the tonguing valleys become narrower and more incised.
Parent materials comprise interbedded coarse soft sandstone and mudstone of the Ganduman Formation. In the narrow valleys, coarse- and medium-textured alluvia have been deposited. The majority of this area is under lowland dipterocarp forest, in which the species Shorea acuminatissima, Shorea macroptera, Shorea smithiana, Shorea multiflora, Dipterocarpus caudiferus and Dipterocarpus confertus are prominent.