Tectonic and volcanic influences on the development and diachronous termination of a tertiary tropical carbonate platform

The demise of carbonate platforms has variously been related to factors suc h as tectonics, influx of clastic material, and environmental stress, somet imes in combination with eustatic fluctuations. However, the precise contro ls on foundering of platforms are often poorly understood. In Sulawesi, Ind onesia, the extensive syntectonic Tonasa Carbonate Platform, of Eocene to m iddle Miocene age, developed to the west of a volcanic are and is overlain by middle to upper Miocene volcanics. These carbonates provide a unique opp ortunity to study the effects of tectonic and volcanic activity on the deve lopment and subsequent demise of a carbonate platform. Detailed held and laboratory analysis of the Tonasa Formation reveal that t he shallow-water deposits of the Tonasa Carbonate Platform had their greate st areal extent in the late Eocene. Although a variety of factors influence d platform development, tectonics and volcanism were particularly important , influencing platform evolution and diachronous termination in four main w ays: (1) During the Paleogene, calc-alkaline volcanic activity limited the eastward lateral extent of the platform but had little effect on carbonate sedimentation in western South Sulawesi, (2) Faulting in the latest late Eo cene resulted in seg mentation of the platform and caused localized drownin g in hanging-wall areas and subaerial exposure on adjacent footwall highs. (3) A further phase of faulting in the early to middle Miocene, just prior to and during the early stages of renewed volcanism in western South Sulawe si, resulted in reactivation of faults, localized tilting of fault blocks, formation of new graben, and subaerial exposure of faulted footwall highs. (4) In the middle Miocene, the influx of volcaniclastics close to volcanic centers rapidly buried most of the few remaining areas of shallow-water car bonates and inhibited renewed carbonate production. However, carbonate prod uction contemporaneous with volcanism occurred in more distal, or localized , areas shielded from volcaniclastic input.