Sedimentological architecture of the Ballik continental carbonates, SW Turkey, as reservoir analogues

Since the recent discovery of important Pre-Salt continental carbonate plays, the need for studying non-marine carbonate reservoir analogues has become important. In the Denizli graben (SW-Turkey), kilometer-wide outcrops of... [ view full abstract ]

Since the recent discovery of important Pre-Salt continental carbonate plays, the need for studying non-marine carbonate reservoir analogues has become important. In the Denizli graben (SW-Turkey), kilometer-wide outcrops of continental carbonates are exposed in several large quarries. Based on outcrop and borehole information the vertical thickness locally can be over 120m thick. Line drawings and sampling of different facies formed the framework for allowing us to work out a detailed sedimentological, diagenetical, geochemical and petrophysical characterisation. Subsequently the geobody evolution was placed into a geodynamic setting. The system starts with a sequence of dominantly sub-horizontally laminated carbonates with pseudo-fenestral porosity which reflect sub-aqueous depositional conditions. Within this succession are non-carbonate intercalations which correspond to initial palaeosol development or flat erosional events. Subsequently a non-carbonate succession (>15m thick), sharply cuts the carbonates. Marls dominate, however, locally channel-shaped conglomerates cut into the marls. The marls are interpreted as sub-aqueous systems because locally varve type structures occur. The conglomerates correspond to braided river deposits. This siliciclastic succession likely reflects a change in climate. These deposits are covered by sub-horizontally laminated carbonates in which over time reed moulds represent the colonization of the sub-aqueous setting by plants. Reed colonies formed traps for sediment particles, and the reed stems themselves served as nucleation surfaces, finally creating topographic irregularities, i.e. reed phytoherms, explaining the subsequent development of inclined dendrite and crystalline crusts reflecting some slope facies development. The progradational behaviour of the slope facies further increases the topography and creates local vertical cliff-like structures on which steeply inclined carbonate deposition developed with overhanging bryophytes. The latter explain the development of metre-sized caverns in what is interpreted as waterfall facies. Between the waterfall structures, depressions gradually become filled up by particulate carbonates, with local development of reed and slope facies. Finally the topographic relief disappeared, and biostromal reed-dominated facies developed before in the central study area some lobe-shaped subaerial prograding carbonate depocentress delivered carbonate particles to the west where a sub-aqueous depositional setting developed. The latter clearly received more siliciclastic input. Finally the carbonate production stopped and siliciclastics (marls, (cross-stratified) sandstones and conglomerates) cover the entire system. The entire studied succession corresponds to a kilometer-wide and long dome structure, similar to the huge continental carbonate feeder dyke systems, also encountered in the Pre-Salt.