Diagenesis and fracturing of a large-scale, syntectonic carbonate platform

Abstract

Please cite this article as: Arosi, Hamed A., Wilson, Moyra E.J., Diagenesis and fracturing of a large-scale, syntectonic carbonate platform, Sedimentary Geology (2015), AbstractThe influence of coeval tectonics on carbonate platform development is widely documented, yet the diagenesis of such syntectonic platforms is barely evaluated.An outcrop, petrographic and geochemical study details here for the first time the diagenesis of the Tonasa Limestone developed in an extensional regime in central Indonesia. This equatorial carbonate system was affected by block faulting, tiltblock rotation, differential uplift and subsidence throughout its Eocene to Early Miocene history (Wilson, 1999;Wilson et al., 2000). The Tonasa carbonate platform is dominated by alteration in shallow to deeper burial depths by fluids with predominantly marine precursor origins.Mechanical and chemical compaction features are common, as are a range of mainly burial-related granular mosaic, blocky and equant calcite cements. Earlier marine cements and meteoric influences are rare, being highly localised to block faulted highs and/or bathymetrically upstanding platform margin areas. Early marine micritisation ofallochems was common on the platform top. Tectonic uplift together with a major oceanic throughflow current are thought to be key influences on localised karstification, meteoric diagenesis and marine cementation. The distribution and orientation of faults, fractures and calcite veins together with evidence for their relative timing are the strongest manifestation of tectonism coeval with diagenesis. There is concordance in the orientation and timing of structures affecting the Tonasa Platform with those basin-wide, with the potential for reactivation of pre-existing basement fabrics.Tectonic subsidence, including fault-associated differential subsidence, controlled the degree of burial diagenesis impacting different areas of the platform. A predominance of burial diagenetic features and dearth of earlier marine or meteoric cementation is seen in other Tertiary equatorial platforms and is partly attributed to: (1) predominance of non-framework building larger benthic foraminifera and/or algae that are prone to remobilisation, have low production rates and limited potential to build to sea level, and (2) high runoff due to the equatorial humid climate contributing to lowered marine salinities in SE Asia.Underlying tectonic reasons for the preponderance of a "regional" diagenetic signature over a "syntectonic" one, fracturing excepted, are: (1) development on the flanks of a backarc basin not on typical continental crust, (2) key platform influencing structures are oblique to the main extensional direction in the basin, and (3) development in an overall subsiding tectonic regime, post-dating basin initiation. The aim here is that this study will contribute to understanding diagenetic alteration of syntectonic carbonate platforms, and those from equatorial regions.

Diagenetic history of late Oligocene-early Miocene carbonates in East Sabah, Malaysia

“…The diagenesis of Gomantong Limestone is similar to other Tertiary platforms from neighbouring islands of Borneo such as Tonasa Platform (Sulawesi, Indonesia) [7] which showed limited early diagenesis (marine or meteoric) together with prevalent of dissolution, cementations and compaction that is related to shallow to deeper burial diagenesis [6][7][8]. The types and morphology of cement are discuss in the subsequent sections ( Figure 4A-4F):…”

Unravelling the depositional origins and diagenetic alteration of carbonate breccias

“…3l) Fig. 4) and occupy a narrow range consistent with or slightly more positive than the expected range of normal marine waters for SE Asia (-1‰ to +1‰ δ 13 C V-PDB; Ali, 1995;Wilson and Evans, 2002;Madden and Wilson, 2012;2013;Wilson et al, 2013;Arosi and Wilson, 2015).…”

“…Known regional δ 18 O‰ V-PDB values for Oligo-Miocene SE Asian marine components and cements plot within a range of -7.1‰ to -1.4‰ (Ali, 1995;Wilson and Evans, 2002;Madden and Wilson, 2012;2013;Wilson et al, 2013;Arosi and Wilson, 2015). Several of these values are more negative than the global norm and likely represent marine components reflecting lowered marine salinities due to the significant terrestrial run-off in SE Asia (i.e., an apparent brackish signature; Tomascik et al, 1997;Wilson, 2008;Wilson et al, 2013;Arosi and Wilson, 2015).…”

“…Several of these values are more negative than the global norm and likely represent marine components reflecting lowered marine salinities due to the significant terrestrial run-off in SE Asia (i.e., an apparent brackish signature; Tomascik et al, 1997;Wilson, 2008;Wilson et al, 2013;Arosi and Wilson, 2015). The onset and development of stylolites and dissolution seams occurs in moderate to deep burial depths commonly from 500-1000 m (Finkel and Wilkinson, 1990;Lind, 1993;Railsback 1993;Nicolaides and Wallace, 1997;Machel, 2004).…”

“…Although the occurrence of dissolution seams versus stylolites may be most strongly controlled by the compacting lithologies, the prevalence of dissolution seams, is perhaps suggestive of maximum burial depth of 500 m for diagenetic features that pre-date chemical compaction (below; cf. Bathurst, 1987;Railsback, 1993;Nicolaides and Wallace, 1997;Madden and Wilson, 2012;2013;Arosi and Wilson, 2015). Extrapolation of the geothermal gradient from Malaysian wells closest to the Batu Gading outcrops (25 °C/km; Hall, 2002) gives an estimated maximum calcite precipitation temperature of 37.5 °C for all pre-brecciation cements and up to 50 °C for post-brecciation, fracture filling cement.…”