DEPOSITIONAL ENVIRONMENT OF THE TONDO FORMATION AT WAKOKO RIVER, PASAR WAJO AREA, DISTRICT OF BUTON SOUTHEAST SULAWESI

摘要

The research area is located at Wakoko River, north of Bau-Bau on the island of Buton, Southeast Sulawesi Province. The Tondo Formation consists of the Clasic Member and carbonates of the Limestone Member. The formation is underlain by deep marine sediments of the Late Jurassic -Eocene Tobelo Formation, and is overlain by shallow marine sediments of the Pliocene Sampolakosa Formation. The research was carried out on outcrops of the middle part of the Clastic Member of the Tondo Formation where it is composed of interbedded mudstone, sandstone and conglomerate. The aims of the research are to determine the sedimentary environment and the age of this part of the Tondo Formation.The sandstone and conglomerate rocks mostly are composed of terrigenous material and coarsen upward. The alternating mudstone and sandstone contain foraminifera and land plant derived organic material. Sedimentary structures observed included cross lamination and flaser bedding.The Tondo Formation at Wakoko River is interpreted to have been deposited in a deltaic environment with aspects of both tidal and fluvial dominance. Seven cycles of sedimentation are recognized. The alternating mudstone and sandstone interval that forms the lower part of each cycle is interpreted as a series of stacked tidal bundles. The upper part of each cycle is predominantly conglomerate and sandstone and these rocks are interpreted to have been deposited in a fluvio-deltaic channel system. Based on the planktonic foraminifera, the age of the Tondo Formation at the Wakoko River is Late Middle Miocene (N14).