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Smith, Randall Blain 1983 Sedimentology and Tectonics of a Miocene Collision Complex and Overlying Late Orogenic Clastic Strata, Buton Island, Eastern Indonesia, PhD Dissertation, The University of California, Santa Cruz.

    © Randall Blain Smith, 1984. Use of any part of this thesis for any purpose must be acknowledged.


Buton exposes a Middle Miocene collision complex and overlying, less-deformed clastic strata derived from erosion of the uplifted complex. In the Wolio Complex, the lower part of an ophiolite sequence is juxtaposed with Triassic to Upper Eocene or Oligocene sedimentary rocks (Turumbia sequence) in an imbricate series of west-dipping thrust sheets. Deep water limestones of the Turumbia sequence formed the deeper portion of a long-lived, carbonate continental margin, and similar rocks and structures can be traced northward along the east coast of Sulawesi to the East Arm, where the continental Sula platform has been thrust westward beneath a large, ophiolite complex. The ages of collision-generated coarse clastic strata indicate that collision occurred significantly later in the East Arm (Late Miocene) than in Buton (Middle Miocene), but contemporaneous with volcanism in the western arc of Sulawesi. The Buton-eastern Sulawesi collision zone apparently evolved from a west-dipping subduction zone by means of northward-migrating collision of the Sula platform. During collision, the Turumbia sequence and related strata were stripped from the western margin of the platform and accreted to the collision complex. The Turumbia sequence and Alpine Tethyan sequences show a similar large-scale facies evolution, suggesting similar histories of rifting and subsidence superimposed on evolutionary changes in calcareous microplankton and paleoceanographic setting through time. Previous reconstructions derive the Sula platform from the northern margin of Irian Jaya (western New Guinea), implying that this area formed part of the southern margin of the Tethys Ocean during Mesozoic time. Middle to Late Miocene clastic strata in Buton (Tondo Formation) are mostly bathyal marine sediments which accumulated in two separate sedimentary basins. The narrow, elongate Lasalimu basin formed just east of the uplifted ophiolite thrust front, which provided most of the coarse detritus to the basin, forming coastal fan-deltas and other slope and base-of-slope deposits. The turbidite sandstone and mudstone facies of the Langkalome basin accumulated to the west of the uplifted ophiolite belt. Typical facies sequences indicate subsidence outpaced deposition during the later stages of clastic sedimentation, possibly in response to the northward departure of the colliding Sula platform and its replacement by oceanic crust outboard of the collision complex.


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