Tectonic and Volcanic Influences on the Development and Diachronous Termination of a Tertiary Tropical Carbonate Platform

Abstract

ABSTRACT The demise of carbonate platforms has variously been related to factors such as tectonics, influx of clastic material, and environmental stress, sometimes in combination with eustatic fluctuations. However, the precise controls on foundering of platforms are often poorly understood. In Sulawesi, Indonesia, the extensive syntectonic Tonasa Carbonate Platform, of Eocene to middle Miocene age, developed to the west of a volcanic arc and is overlain by middle to upper Miocene volcanics. These carbonates provide a unique opportunity to study the effects of tectonic and volcanic activity on the development and subsequent demise of a carbonate platform. Detailed field and laboratory analysis of the Tonasa Formation reveal that the shallow-water deposits of the Tonasa Carbonate Platform had their greatest areal extent in the late Eocene. Although a variety of factors influenced platform development, tectonics and volcanism were particularly important, influencing platform evolution and diachronous termination in four main ways: (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 Eocene resulted in segmentation of the platform and caused localized drowning in hangingwall 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 Sulawesi, 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 carbonates and inhibited renewed carbonate production. However, carbonate production contemporaneous with volcanism occurred in more distal, or localized, areas shielded from volcaniclastic input.