3). In the first cycle between 6250 ± 250 and 2600 ± 250 years BP, sedimentation was slower (∼1 m/ka) compared to the second cycle after

1470 ± 60 years BP (∼2 m/ka). This depositional history shows that the Chilia I lobe developed in two phases. A smaller proto-Chilia distributary started the lobe growth after 6500 years BP in the same time as the Tulcea bayhead lobe grew adjacently to the south (Carozza et al., 2012b). Occurrence of benthic foraminifera (i.e., Ammonia sp.) find more at the base of our core indicates that the Pardina basin was connected to the sea at the time. Because contemporary deposits of the Tulcea lobe to the south record only freshwater fauna ( Carozza et al., 2012b) this connection of the Pardina basin to the Black Sea was probably located at the Chilia loess gap. The hiatus between the two deltaic cycles ( Fig. 3) indicates that the proto-Chilia distributary diminished its discharge or ceased to be active after ∼2600 years BP and was reactivated or rejuvenated after ∼1500 years BP. By the time that PD0332991 supplier this new distributary began to build a new lobe beyond the Chilia loess gap, the growth of Chilia I lobe was probably largely completed. Chilia II lobe presents a typical bayhead delta morphology (e.g., Bhattacharya and Walker, 1992)

with multiple distributaries bifurcating primarily at its apex at the Chilia loess gap (Fig. 2b). This channel network pattern, along with a lack of interdistributary ponds, suggests that the new lobe developed by filling the East Chilia basin in a sweeping and rapid west-to-east migration. Although most of the Chilia water flows now along several central anastomosing channels, natural levee deposits are less developed than in the older upstream lobe. Lack of below secondary channels intruding into the basins south or north of the East Chilia basin (Fig. 2c) suggests that the basin was completely confined as the Chilia II lobe grew. The Letea strandplain and the Jebrieni spit separated the East Chilia basin from the Black Sea whereas the Tulcea lobe extension into the Matita-Merhei basin

along with the Rosca-Suez strandplain confined the basin in the south and the lagoonal Sasic strandplain confined it in the north. The presence of marine fauna such as foraminifera (Ammonia sp.) and bivalves (Cardium edule) above loess deposits at the base of our core collected at the apex of the Chilia II lobe ( Fig. 2) indicates that the East Chilia basin was initially a lagoon connected to the Black Sea. Above the fine grained lagoon sediments, the deposits of the Chilia II lobe exhibit a typical but thin succession of fine prodelta deposits and delta front sands with interstratified muds that are capped by organic-rich fines of the delta plain and soil. A radiocarbon date at the base of the delta front deposits indicates that the Chilia II lobe started to grow at this proximal location at 800 ± 130 years BP ( Giosan et al., 2012).