Tectono‐Sedimentary Evolution of the Neogene İnegöl Basin ( NW Anatolia): Constraints on Transtensional Basin Development at the Junction of the Western Anatolian Extensional Province and the North Anatolian Fault Zone

Neogene crustal extension and associated basin formation in western Anatolia were followed by back‐arc retreat of the Aegean subduction and westward extrusion of the Anatolian Block. Located at the junction of Western Anatolian Extensional Province and dextral North Anatolian Fault Zone, the İnegöl Basin is characterised by terrestrial deposition within a transtensional setting. During the initial phase of extensional deformation in the İnegöl domain, the NW‐trending Bursa and Oylat faults evolved into dextral‐shear at ~17 Ma which was coeval with terrestrial deposition containing early Astaracian (MN6) fauna, unconformably overlain by the Palaeozoic basement of the Uludağ Massif. Progressive right‐lateral displacement along the Oylat Fault, accompanied by the uplift of the Uludağ Massif, led to the development of a relay ramp between the Saitabat segment of the Bursa and the Oylat faults to the south. Uplift of the Uludağ Massif reached the surface at approximately 9.2 Ma, coinciding with intensified Late Miocene deformation along the southern branch of the North Anatolian shear zone in the southern Marmara domain at ~10 Ma. During this period, obliquely oriented transfer faults linking the Saitabat and Oylat faults were promoting renewed basin subsidence in the Late Miocene. Fossil assemblages from the basal basin‐fill deposits indicate subsidence during the Vallesian (MN9–10), characterised by alluvial to fluvial depositional environments. Continued tectonic subsidence facilitated the establishment of lacustrine environments during the Turolian (MN11–13), marking a relatively tectonically stable period that persisted into the Pliocene. Westward propagation of the North Anatolian Fault into the southern Marmara region was largely accomplished by the Pliocene. Under this new tectonic regime, the İnegöl Basin became longitudinally subdivided into two sub‐basins by cross‐basin normal‐oblique fault dominated by dextral strike‐slip motion. During the Early Pleistocene (MN17), uplifted Neogene sediments were eroded and redeposited into newly formed depressions, as documented by the corresponding faunal record.