Akademik Veri Yönetim Sistemi
Carbonates and Evaporites, cilt.40, sa.2, 2025 (SCI-Expanded, Scopus)
The Early Jurassic to Late Cretaceous succession of the Central Sakarya Basin in the Bilecik region is predominantly composed of carbonate rocks and was deposited on the passive margin of the Sakarya Continent in association with the northward subduction of the Tethys Ocean. The current work aims to explain the microfacies types, facies belts, and palaeoenvironments of the Jurassic-Cretaceous succession of the Bilecik Carbonate Platform developed in this basin. Our study presents field observations, petrographic investigations, facies analyses, and lithocorrelations. The lithological units identified consist of cross-bedded sandstones and pebbles, limestones, lime mudstones with chert nodules, and volcanic interbeds. The carbonate deposits that overlie the river deposits represent the Bilecik Carbonate Platform. In this carbonate succession, five distinct microfacies were identified: oolitic grainstone (MFS-1), coated bioclastic grainstone (MFS-2), bioclastic wackestone (MFS-3), pelagic lime-mudstone (MFS-4), and lithoclastic packstone (MFS-5). These microfacies reveal that the Jurassic-Cretaceous carbonates were deposited across various sedimentary facies belts, including platform margin sand shoals, organic buildups, open marine, toe-of-slope, and slopes. These deposits span a depth range from shallow marine to deep marine. The relatively shallow water depths where the MFS-1, MFS-2, and MFS-3 microfacies developed are characteristic of the inner-shelf environment and are typically influenced by wave and tidal processes. In contrast, MFS-5 microfacies, which developed at deeper water depths, represent the mid-shelf environment generally dominated by storm waves. The MFS-4 microfacies, in turn, represent the outer-shelf environment below the storm wave base. The diversity of microfacies and environments indicates significant changes in depositional depth and energy conditions during the development of the Jurassic-Cretaceous carbonate deposits. In addition, the Jurassic-Cretaceous carbonates were influenced by various diagenetic processes, including micritisation, cementation, compaction, and fracturing. These processes reflect different diagenetic environments: marine, meteoric, burial, and uplift. In conjunction with field observations, evaluating microfacies, facies belt types, and diagenetic processes observed from the bottom to the top of the succession indicates that transgressive sedimentation occurred in the southern part of the Central Sakarya Basin. This sedimentation, which moved from the inner to the outer shelf environment, responded to sea-level changes from the middle Jurassic to the late Cretaceous.