The Tapang Association occurs on low hills and terraces in the Labuk and Karamuak valleys. A notable occurrence is on the broad lowland linking the Labuk valley at Telupid with the Karamuak valley at Enteleben.
The low hills are up to 30 m in amplitude with slopes of less than 15°.They are surrounded by slightly undulating terraces. The hills are formed of basic igneous rocks and the terraces are formed of alluvium derived from adjacent mountains of basic and ultrabasic rocks.