Depositional architecture of a wave-dominated shoal-water fan delta (Manavgat Basin, southern Türkiye): implications for the Middle–Late Tortonian sea level changes and tectonics

Abstract

This study describes the sedimentary facies associations of the İhtiyarlı shoal-water fan delta complex in the Manavgat Basin, south Türkiye, to interpret the forces acting on base-level changes and the basinal processes controlling sedimentation. The fan delta complex sharply overlies the offshore transition deposits. It consists of three main fan delta wedges, each composed of several mound-shaped delta lobes of the shoal-water deltas stacked upon one another with a lateral offset. The first delta wedge deposited by forced regression consists of deltaic shoreface, delta-front beach, and fluvial distributary channel deposits, indicating that the fluvial sediment discharges exceeded the rate of frontline marine reworking. The overlying deltaic wedges deposited by normal regression consist only of deltaic shoreface and delta-front beach facies, which are attributed to less incised river channels no longer promoting sediment delivery, while seaward protrusion made the delta front more vulnerable to wave action. The normal regressive delta wedges are considered to be parasequences, implying episodic drowning of progradational wedges due to minor subsidence episodes or eustatic sea level rise. The thick and laterally extensive delta-front beach facies overlying the deltaic shoreface sediments formed in both forced and normal regressive wedges, indicating that the fan deltaic shoreline was subjected to wave-dominated marine processes during and after deposition. The biostratigraphic dating of the İhtiyarlı fan delta complex suggests an age of approximately 9.54–7.80 Ma, which can be assigned to the zonal interval from the middle part of Zone MMi 11 to the lower part of Zone MMi 12 of the Late Tortonian, based on planktonic foraminifera from the underlying mudstones and heterolithic deposits just beyond the shoal-water deltaic wedges toward the basin interior. The İhtiyarlı fan delta complex began to develop in response to the Middle–Late Tortonian relative sea level fall that partially exposed the Manavgat Basin, indicating a regional forced regression. Due to the forced regression corresponding to the transgressive part (9.2–7.62 Ma) of the third-order eustatic sea level cycle of post-Tor2, we interpret this event as related to the tectonic uplift of the Tauride Mountains. © The Author(s), under exclusive licence to Springer Nature Switzerland AG 2024.