Sedimentology and Miocene-Pliocene depositional evolution of the stream-dominated alluvial fan deposits at circum-Sultandağları region

Abstract

Yalvaç and Ilgın basins surrounding the Sultandağları opened due to orogenic collapse in the early Miocene. The NW-SE trending Çakırçal and Akşehir Faults, forming boundaries with these basins, caused both opening of the basins and uplifting of the Sultandağları. During the Miocene-Pliocene period, alluvial fans fed from the Sultandağları developed on the basin margins, while lacustrine carbonate and clastic depositions occurred in the basin's interior. Alluvial fan sediments are laterally and vertically transitional with lacustrine sediments and alternate several times in the sequence. Alluvial fans, widespread in the region, consisting of "debris flow", "high density stream flood", "braided river" and "meandering river" deposits. Fan deposits that pass from the high-energy fluvial facies at the basin margin to the low-energy fluvial facies towards the basin interior have been interpreted as "stream-dominated alluvial fan deposits". Age data obtained from the fan deposits of the Yalvaç and the Ilgın basins show that the Sultandağları concurrently feeds the alluvial fans on both flanks. Alluvial fan deposition around the Sultandağları occurred under the control of tectonic and climatic processes. Tectonism led to the formation of basins and the creation of source areas. Simultaneously, the climate maintained the streams to be perennial by precipitation, thus proving a continuous sediment supply to the basins. Tectonism and climate-controlled base-level changes determined the quantity of sediments carried to the basin from the source area, causing regressive or transgressive developments.