GEOLOGY AND STRATIGRAPHY

The simplified geology of South Buton is presented in Figure 1 below. The stratigraphy will be described very briefly in the following. The stratigraphic column is presented in Figure 2.

Figure 1. Simplified Geology of South Buton

with location of asphalt field

Wapulaka Formation

This Pleistocene – Holocene Formation is a raised coral reef consisting of decrial sedimentary corals, chalk-like limestone, clays and globigerina bearing marl. This formation overlies conformably the Sampolakosa and unconformably older beds. It forms a karstified topography and locally slightly tilted reef terraces. The thickness varied to a maximum of 700 m.

Sampolaka Formation

In general this Miocene – Pliocene Formation is made up of marly Limestone – Marl series with end series of marly limestone and limey marl, limey sandstone, chalk rich in foraminifera and locally mollucs. The thickness may exceed 750 m. Locally it consists of calcarenite, micritized limestone, marls and sandstone. This formation overlies conformably the Tondo Formation.

Figure 2. Schematic stratigrapy of Buton

(Wiryosujono and Hainim, 1975)

Tondo Formation

This Middle – Upper Miocene Formation consists of conglomerates and sandstones alternating with clay and marl beds. The conglomerates originates from boulders of Mesozoic sedimentary rocks peridotites and serpentines, and lesser amphibolites and quartz clasts. The thickness is possibly hundreds of meters.