Publications

Tarakan Basin is a unique Tertiary Basin, particularly from structural geology point of view. The basin is situated on Northeast Kalimantan which has endured several tectonic events. The most discussed topic is its gravitational fault system related to deltaic sedimentation. The structural trend is majorly NE-SW in direction since the source of sediment is located in Central Kalimantan Mountains Range to the west. However, another major NW-SE structural trend is present in the Bunyu, Tarakan, Ahus and Sebatik arches. This NW-SE trend is in contradiction to the gravitational fault mechanism, indicating influence from another mechanism. The NW-SE structural trend is interpreted as the product of transpression-force which created strike-slip fault through the region. The structure can be seen from our 2D seismic image on the Simenggaris Area (Figure 3). The characteristic of the strike-slip fault in this area is having a high-dip angle fault with many branches identified as the well-known flower-like structure. The fault surface is also relatively planar whilst the growth-fault is more curved or listric in geometry. We have mapped the subsurface and it reveals that the strike slip does not only trend in NW-SE direction but also it has NE-SW trend, which possibly means that the strike-slip fault has reactivated the old-structure. The strike-slip event is the latest tectonic episode considering its fault cross-cutting relationship. Therefore positive structures near the strike-slip fault have the higher prospectivity for hydrocarbon accumulations. This interpretation is supported by the presence of several petroleum fields near the NW-SE structural trend such as: Bunyu, Tarakan, Sembakung, etc.