The Neogene Osmaniye-Bahçe sub-basin and neighbouring sub-basins of the same age (İskenderun-Arsus-İA, Hatay-Samandag-HS) are located near the triple junction of the Anatolian, African and Arabian plates in the easternmost part of the Mediterranean region, (Bay of İskenderun, southeastern Turkey). These sub-basins are surrounded by the Misis Uplift to the west, the Taurus Mountains to the north, the Amanos Uplift to the east and the Karataş-Osmaniye Fault, a segment of the East Anatolian Strike-Slip Fault, to the southwest. Strike-slip tectonics strongly affected Neogene and pre-Neogene sediments of the area. The first marine transgression took place in the Middle Miocene that resulted in the deposition of patch reefs with minor siliciclastic input in the local lagoons and shoals. Shallow shelf areas over the topographic highs provided suitable hard substratum for the colonization by corals and other reef builders. The patch reefs, i.e., the Horu Formation, mainly comprise reef cores and flanks. The reef cores are lenticular, massive bodies characterized by corals in in situ growth positions that are of thin to thick branching, massive domal and platy morphologies, while reef flanks and peri-reefal areas are mainly composed of reworked coral blocks and bedded biogenic limestones. In the early Late Miocene, the reefs prograded across the shelf margin due to sea level rise and then were gradually replaced by deltaic sediments (Kızıldere Formation). The early phase of deltaic deposition is represented by vertical and lateral transitions with lagoon-estuary sedimentary systems and small-scale Ostrea reefs associated with carbonate and siliciclastic interbeds. The most important controlling factors for the sedimentation in these sub-basins were antecedent topography, clastic input, sea level changes and syn-sedimentary tectonics.