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Archaeological data provide evidence of human inhabitation in the Danube Delta since the Early Neolithic with once flourishing human settlements such is the case of Enisala and Babadag settlements. Their remains dating back from Eneolithic (Enisala) or Iron Age (Babadag) or from their revivals in Antiquity and Medieval Age have been found on higher grounds (i.e. hillslope terrace) in the immediate vicinity of Babadag and Razelm lakes and of the reedmarsh developed in-between the lakes. The settlements benefited from their strategical position defined by the intersection of the terrestrial routes linking the northern and southern Dobrudja with the navigation ways to the Black Sea via a shallow but open lagoon prior to Antiquity and later, post 7th c. BC, via Dunavaț branch of the Danube that extended the southern delta by successive open-coast deltaic lobes formation (2600-1300 yrs BP). This study documents the landscape transformation of the region since Early Neolithic to the present, based on sedimentological, chronostratigraphic, mineralogical, geochemical, magnetometric, macro- and microfauna analyses which altogether led to the identification of main stages: i) high floodplain (before 8000 BP), ii) wetlands (8000-7500 yrs BP), iii) shallow marine bay (7500–6000/5500 yrs BP), iv) lagoon (5500-460 yrs BP) and v) reedmarsh (460 yrs BP – present). Each type of landscape that succeeded in the Enisala-Babadag region is described in relation with shoreline position, (ground)water depth and Danube Delta development. Additionally, the tectonic subsidence of the studied wetlands (0.5–0.8 mm/yr) was assessed and its effects on the landscape changes and long-term morphodynamics are discussed.

International audience; This paper documents the Late-Holocene environmental changes and human presence in the northern Danube delta using a multidisciplinary approach that combines geoscientific data with archaeological findings, historical texts, and maps. It follows the formation and progression of the Chilia distributary and the reconfiguration of socioeconomic activities. Sedimentary facies identified on five new cores by changes in texture properties, magnetic susceptibility, geochemistry, and macro- and microfauna composition together with the newly obtained chronology constrain the complex evolution of the Chilia branch as filling in a long-lasting bay and then of a giant lagoon (Thiagola) which covered most of the northern delta since the Old Danube lobe inception (ca. 7500 yrs BP) till modern Chilia development. It initiated during the Greek Antiquity (ca. 2500 yrs ar BP) at the delta apex, while in Roman times (ca. 1800 yrs BP) it pursued its slow flowing into the vast Thiagola Lagoon. The most dramatic transformations occurred in the last 800 years when the river passed east of the Chilia promontory, rapidly went through the present-day Matița-Merhei basin (several decades), and created its first open-sea outlet. Solid discharge increased in two distinct periods, once in the Middle Ages (ca. 750 yrs BP) and then in the Modern Period (ca. 150 yrs BP) due to human-induced land-use changes in the Danube watershed. The chronology of the cultural remains on the pre-deltaic Chilia promontory and the multiproxy analysis of a sediment core retrieved nearby downstream suggest the terrestrial connection of the island with the mainland in ancient times. The hitherto contended issue of the old Thiagola Lagoon and its location are redefined here, as are the original identifications of ancient and medieval toponyms and hydronyms, especially for Chilia-Licostomo, Byzantine, Genoese, Moldavian, Ottoman, and Russian trading point of great importance in the political and economic history of the Black Sea and neighboring regions.

Phaeozems with very deep mollic topsoil overlying a cambic B horizon occur in a patchy distribution in Eastern Romania, in areas where present climatic conditions are rather favourable for forest soils development. Due to their unusual characteristics, it has been hypothesized that the main factors implied in their development could be related to the prehistoric habitation and climate changes during the Holocene, but this approach was never explored. In this context, an archaeological excavation into an Eneolithic (5000–3500 BCE) settlement located in north-eastern Romania offered the opportunity to investigate pre- and post-Eneolithic development of these soils. Fifty soil samples were collected above and below an Eneolithic dwelling floor, between adjacent dwellings and by off-site sampling. A portable X-ray fluorescence (pXRF) spectrometer was used to scan the soil samples and the total element composition of 18 elements was retained for subsequent statistical analysis. The main objective of this study was to analyse the depth functions of elemental contents in relation to the morphological characteristics of these soils in order to infer the pedogenic pathways of their formation. Results showed increased concentrations of P, Sr, Ca, Cu and Zn above the Eneolithic layer relative to the control soil profile, as a result of both prehistoric and recent anthropogenic activities, but similar trends bellow the dwelling remnants and between adjacent dwellings, which suggest the relict character of the pre-Eneolithic soil. The geogenic elements like Al, Fe, K, Rb, and V are highly correlated, have similar curve shapes in all analysed profiles and generally increase with depth, starting from the pre-Eneolithic land surface. The variability of Ti, Zr and Ti/Zr ratio shows a clear contrast in the upper part of soil profiles and a similarity below the Eneolithic level. Statistical analysis also confirms at least two major phases in the evolution of these soils. The application of the Pettitt test placed most of the elemental changes at the depth were the upper soil welded to the buried Eneolithic soil. Therefore, our study demonstrates the utility of Pettitt test in detecting pedogenic thresholds, besides its traditional use for time series analysis. The characteristics of the pre-Eneolithic soils support the hypothesis that they were already formed in the mid-Holocene, which constituted the prerequisite for the beginnings of human habitation and agriculture in this area. It can be concluded that the successive changes of climate and the land use since the mid-Holocene until present are likely the main factors that controlled the formation of the upper part of these overthickened soils, resulting in an incipient Luvic Phaeozem, which extended and welded downward to a relict Cambic Chernozem.