Stratigraphy of Salodik Formation in Batutambung section, Toili, Luwuk, Central Sulawesi

Abstract

Salodik Formation is one of the formations representing a continental drift sequence prior to the collision of Banggai Basin, and it was widely cropped out in the East Arm of Sulawesi. The published geological maps of Luwuk dan Batui describe the Salodik Formation as massive and bedded limestone with marl intercalated and sandstone in the lower part, ranging from Eocene to Late Miocene. In Batutambung, Toili, the geological maps showing the Salodik Formation distributed in a NW-SE trend between two ophiolitic land masses, and suggesting intensive tectonic deformation along the trend. Preliminary geological investigations in this area show that Salodik rock sequences varied from other Salodik outcrops in different areas. Detailed stratigraphic measurements and rock sampling have been carried out along the road connecting Toili and Ampanan Tete., yielding a measured stratigraphy of 70 m vertically thick. Nine lithofacies were identified, i.e., coarse-grained sandstone (cS), micritic sandstone (mcS), fine-medium-grained sandstone (fmS), sandstone with coal spar (SMms), Mudrock (mM), micritic mudrock (mcM), Mudstone (MS), Wackestone (WS) and Packstone (PS). Facies association shows the rock sequence has shallowing upward or prograding pattern with depositional environment varies from an open marine, tidal channel, shoal, and restricted marine/ lagoon Based on foraminifera and nannofossil analysis, Salodik Formation in Batutambung section was deposited in Early Miocene (N6 or NN4-NN6), with paleobathymetry from middle to outer neritic. Based on its age and lithology character, the Salodik Formation in Batutambung is equivalent with Matindok Formation in Tomori PSC.