Types of carbonate platforms : a genetic approach

Abstract

Many types of carbonate platforms have been described, from homoclinal ramps to rimmed shelves and a full spectrum of variations in between; the distinction between these different types can be problematic. Nevertheless, classi®cation of carbonate platforms is not just a semantic or academic issue. For example, it is clearly important for the accurate interpretation of seismic images of facies geometry and for assessing the potential of stratigraphic traps. Even though predictive ef®ciency of conceptual models depends on the degree of comprehension of the genetic factors controlling depositional pro®les and the distribution of facies belts, current models for classi®cation of carbonate platforms are basically descriptive and mainly based on depositional pro®le, size, and attachment to or detachment from a landmass.A genetic approach considers the variability of depositional pro®les among carbonate platforms as a function of the type of sediment that was produced (basically grain size), the locus of sediment production, and the hydraulic energy. Three groups of carbonate-producing biota may be distinguished according to their dependence upon light: (1) euphotic (good light) in shallow, wave-agitated areas; (2) oligophotic (poor light) in deeper, commonly non-wave-agitated areas; and (3) photo-independent biota in all water-depth ranges.Several platform types in wave-dominated seas can be considered in relation to genetic factors, even when simplifying the many possible scenarios. Euphotic framework-producing biota create rimmed shelves similar to modern reef platforms. Soft-substrate-dwelling biota, which produce gravel-sized carbonate in the shallow euphotic zone, create¯at-topped open shelves. Oligophotic gravel-producing biota, such as some larger foraminifera and red algae, generate distally steepened ramps. Mud-dominated carbonate production, in either euphotic or oligophotic zones, generate homoclinal ramps. Carbonate production dominated by photo-independent biota (crinoids, sponges, bryozoans, etc.) above wave base give rise to open shelves or ramps, depending upon grain size, but may produce mounds if carbonate production occurs below the base of wave/current sweeping.

Development of transient carbonate ramps in an evolving foreland basin

“…The relative proportion of allochems was estimated in thin sections using the Baccelle & Bosellini comparison charts (Fl€ ugel, 2010). The environmental interpretation of carbonate microfacies and biota follows the existing carbonate-ramp models and seminal case studies (Buxton & Pedley, 1989;Burchette & Wright, 1992;Handford & Loucks, 1993;Pomar, 2001a;Romero et al, 2002;Bosence, 2005;Scheibner & Speijer, 2008;Bassi & Nebelsick, 2010;Brandano et al, 2015). The distinction of shallow benthic foraminifer biozones (SBZ) is according to Serra-Kiel et al (1998).…”

“…Palaeoenvironmental reconstruction of carbonate ramps may be straightforward in passive-margin shelf settings (Read, 1985;Burchette & Wright, 1992;Pomar, 2001a), but is more difficult in foreland basins (Read, 1980) where the preservation of such features is often poor and where tectonic deformation obscures both primary bathymetric gradients and palaeogeographic context. A similar difficulty in foreland carbonate successions pertains to the recognition and dating of short-term (<1 Ma) bathymetric changes, which are crucial to a high-resolution sequence stratigraphy and to the distinction of eustatic and tectonic forcing in the basin history.…”

Impact of storms on mixed carbonate and siliciclastic shelves: insights from combined diffusive and fluid‐flow transport stratigraphic forward model

“…15^251) depositional slope in the distal part. Moreover, homoclinal to distally-steepened ramp evolution has been documented many times for the Phanerozoic (Wilson, 1975;Read, 1982Read, , 1985Wright, 1987;Pomar, 2001).…”

“…The Miocene sediment pulse corresponds to the development of large-scale progradational features across the North Atlantic margin (Greenlee, 1988). Depositional pro¢les of carbonate shelves have been proven to be in£uenced by the amount and type of carbonate sediments produced, and by the depth at which production is most e⁄cient (Pomar, 2001). Avolume-based calculation of carbonate accumulation rates applied to the Mesozoic platforms of the Paris basin has revealed values ranging from 5.5 to 67 m Myr À 1 (Dromart et al, 2001).…”

A prograding margin during global sea‐level maxima: an example from Mahajanga Basin, northwest Madagascar

“…The package displays a typical rimmed platform morphology (e.g. Pomar, 2001;Fig. 4) that is aggradational from SS1 to SS2.…”