Deciphering depositional controls and evolution of a lacustrine supradetachment basin through facies analysis: Gördes Basin, Western Türkiye

The lacustrine Gördes Supradetachment Basin developed along the Simav Detachment Fault during the Early–Middle Miocene postorogenic extension in the north of the Menderes Massif in western Anatolia. The basin‐fill consists of alluvial fan, Gilbert‐type delta, shoal‐water delta, foreshore, shoreface, offshore‐transition and peat‐forming mire deposits. The alluvial fans and fan deltas deposited along all the margins serve as sensitive recorders of tectonic, climatic, and base‐level variations. Process‐based facies analyses of the alluvial fan and fan‐delta deposits provide an excellent opportunity to reconstruct the palaeogeographical evolution. The alluvial fans consist of braided channel‐fill, hyperconcentrated flow and debris flow facies, indicating high‐energy sediment transport mechanisms. Progradational wedges of Gilbert‐type fan deltas formed atop the alluvial fans reflect a rapid rise in lake level. This rise resulted from asymmetrical subsidence of the basin floor, which shifted the water mass laterally, causing rapid regression on one coast and coeval transgression on the other. Changes in basin floor configuration in the Gördes Basin were driven by movement of the Simav Detachment Fault on the southern margin, while the hanging wall was segmented by an antithetic normal fault on the northwestern margin. Consequently, faulting on both sides increased the depth of the accommodation through a sudden lake level rise. Climate controlled both the lake water budget and the catchment sediment yield. The subsidence rate subsequently decelerated, sediment yield decreased and shallow lake conditions prevailed on the NW margin, as evidenced by the shoal‐water deltas. This occurred due to tectonic activity insufficient to produce the large‐scale deepening required for Gilbert‐type delta development. Finally, the clastic components of the offshore transition facies diminished as the carbonate content increased towards the basin's interior and in the upper parts of the succession during the maximum lake expansion.