TERRAIN, GEOLOGY AND SOILS
Tabin contains a variety of terrain ranging from brackish water swamps at sea-level in the north-east to the central mountain ranges of which Mount Hatton (571 m) is the highest.
Most of the central, western and southern regions of the reserve are dominated by rugged mountain ranges that are dissected by deep ravines and steep-sided river valleys.
In these parts of the reserve there are more than 15 peaks 500 or more metres in height. In addition, there are at least 30 peaks between 300 and 500 metres high.
The northern and eastern regions of Tabin are characterised by flat or gently undulating lowlands between sea level and 100 metres in altitude. Except for the swampy north-eastern quarter there are small hills between 150 and 250 metres high scattered throughout these lowlands, particularly in the areas bordering the central Tabin massif.
The central, southern and western highland regions of Tabin comprise, sedimentary-volcanic formations (see Map, above right). This rock type also covers most of the western half of the northern lowlands except for the southern flanks of the Segama River Valley which are overlaid with alluvium and peat. Alluvium and peat also cover most of the low-lying north-eastern quarter of’ Tabin including the lower portion of the Tabin river valley. To the immediate East of this valley is an area of sedimentary formations. North of that there are a few intrusions of volcanic rock. Sedimentary formations or alluvium and peat accounts for the rock types of the remainder of the Dent Peninsula east of Tabin.
Soil types in Tabin consist predominantly of varieties of mudstones and sandstones, mixed with miscellaneous rocks. There are also fairly large areas scattered throughout the reserve that consist of tuffaceous rocks interspersed with mudstone and sandstone. Some of the flatter river valleys and swampy areas in the north-east of the reserve have alluvial soils or a mixture of alluvium and peat. Bordering such areas in the interior of the north-eastern quarter are patches which consist of a mixture of mudstone and alluvium. Several small ranges of hills in the centre of the northern region have limestone soils but compared with some other areas in eastern Sabah Tabin has very little of this soil type.
MINERALS AND MUD VOLCANOES
The mineral resources of Tabin are not yet fully explored but investigations to date suggest that Tabin contains no known sources of commercially important minerals.
Laterite deposits of a quality useful for road surfacing are found in the western part of the reserve but the geology of Tabin is dominated by the presence of young sedimentary rocks that have little prospect of supporting oil reserves or mineral deposits.
Tabin has several mud volcanoes and salt springs that provide a variety minerals necessary for the health of wildlife. The mud volcanoes are surrounded by open areas up to 200 m in diameter. The central mud volcanoes are raised muddy hills with puddles of dilute, grey mud at their summits. Warm, salty mud bubbles from below the surface every almost continuously. The liquid puddles are surrounded by mud at various stages of desiccation. Periodically the mud volcanoes have mild eruptions that add to their height and scatter small boulders and stones throughout the open area around them. The levels of calcium and sodium and calcium from volcano mud is hundreds of times higher than levels from soils in surrounding areas.
It appears that wildlife use the mud volcanoes as “salt licks” in order to ingest such minerals. Consequently, the tracks of a variety of wildlife species can normally be seen in the drying mud (Plate 5). Since the areas around mud volcanoes are open and animals visit them almost every day the mud volcanoes are useful sites for bird and wildlife observation. This can be done from the vantage point of forest around the perimeters of mud volcanoes and Tabin Wildlife S/B has set up a hide near the Lipad volcano.