Compaction of claystones-shales and limestones penetrated by well TT-1 and TT-2 in the western margin of the South Makassar Basin (SMB) has been evaluated. Each type of lithology exhibits specific porosity-depth relationship which is characterized by an exponential curve. In the study area the relationships are : = 69.e0.000391 for claystones-shales and o 59.e-0.000731 for limestones, where o is the porosity (%) and z is the depth below the top of the sediments.           Those relationships facilitate decompaction of the sediments and hence restoration of their original thick-. nesses. This study indicates that the thicknesses of the sediments have been significantly reduced by compaction. It is evident that basement subsidence during Miocene times should be increased by 100 to 308 m if cotrected for compaction.           Understanding the (basement) subsidence is an important aspect of basin analysis as it facilitates the calcu- lation of the amount of extension from which the formation of sedimentary basin can be modelled.
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