ARTICLE IN PRESS Quaternary International xxx (2010) 1e11 Contents lists available at ScienceDirect Quaternary International journal homepage: www.elsevier.com/locate/quaint Geodynamic and hydro-geological constraints regarding the extension of the prospective archaeo-cultural area within the northern Romanian coastal zone Radu George Dimitriu* Department of Geophysics, National Institute of Marine Geology and Geoecology - GeoEcoMar, 23-25 Dimitrie Onciul Street, 024053 Bucharest, Romania article info abstract Article history: An obvious discrepancy is noticed between the very few archaeological sites discovered until now on the Available online xxx Danube Delta plain area and the large number of such sites, whose ages range from the Middle Paleo- lithic to the Middle Ages and more recently, identified on its higher topography surroundings. Keywords: The combined effects of the regional subsidence of the coast and delta area, with amplitudes of Romanian Black Sea coast À2toÀ4 mm/y and of the secular mean sea level rise (þ0.5/1.0 mm/y) continuously change the “land- Dobruja mean sea level” relative relationship, placing the prospective archaeo-cultural layer corresponding to Geodynamics the Late Prehistory e Antiquity period at a burial depth which now exceeds 4e5 m. This situation Eustasy Littoral erosion partly explains the limited success of the archaeological research carried out until now within the Archaeo-cultural heritage Danube Delta plain area and recommends a systematic use of the geophysical investigation methods in future. The integrated interpretation of the coastal zone bathymetry and sedimentology mappings and of the shoreline geomorphological evolution in time highlights the sedimentary processes that pres- ently shape the littoral study zone allowing to divide it in sectors where either sediments accumu- lation or erosion processes prevail. The study draws attention to the Împut¸ita e Câs¸la Vadanei and Cos¸na e Vadu littoral sectors where the intense marine erosion of the shoreline and the adjacent seabed also imminently endangers their prospective archaeo-cultural load. Ó 2010 Elsevier Ltd and INQUA. All rights reserved. 1. Introduction seabed of the study area, trying to draw special attention to those sectors where marine erosion causes rapid shoreline retreat and The historical region of Dobruja, also known as Dobrogea (in imminently endangers the prospective archaeological heritage. Romanian), Dobrudja or Dobrudzha (in Bulgarian), is located on the western coast of the Black Sea, and is bordered to the west and 1.1. Regional setting north by the River Danube. Today, the region belongs both to Romania (Tulcea and Constanta counties) and Bulgaria (the The main structural units of the regional basement (Fig. 1)are, administrative regions of Dobrich and Silistra). The study area from north to south, the Scythian Platform, represented here by the (Fig. 1), located in northern Dobruja, entirely covers the Danube downthrown compartment of the Pre-Dobruja Depression, the North Delta and its adjacent littoral sector. Dobruja Folded Belt, conventionally confined between the Pece- Although the archaeo-cultural heritage of the Dobruja region is neaga- Camena and Sfântu Gheorghe Faults (the latter is well-known quite impressive, the number of archaeological sites discovered until in the offshore as the Sulina- Tarkhankut Fault; Dinu et al., 2005) and now within the Danube Delta plain area is surprisingly low. The the Moesian Platform, represented by its uplifted Central Dobruja paper synthesizes information on this region’s crustal geodynamics, Unit. The lithological units of the Cimmerian folded belt and Moesian Late Pleistocene e Holocene geological evolution of the Danube Platform are sealed by the post-tectonic late Cretaceous sediments of Delta area, and on the recent eustasy, and tries to make a reliable the Babadag Syncline, extending beneath the young, unconsolidated prediction on the extension and burial depth of the prospective sediments of the southern Danube Delta towards the Histria archaeo-cultural layer corresponding to Ancient times. The paper Depression on the Black Sea continental shelf. The Danube Delta also gives an integrated interpretation of the hydro-geomorpho- sedimentary successions include both marine and lacustrine littoral logical processes which shape the modern littoral and the shallow deposits, fluvial, marsh and loess-like deposits (Panin, 1996). The Late Pleistocene and Holocene evolution of the Danube Delta * Tel.: þ40 723 453 930; fax: þ40 21 252 2594. (Fig. 2) includes the following main phases (Panin, 1999): (1) the E-mail address: [email protected] formation of the Letea-Caraorman initial spit, 9700e5500 BC; (2) 1040-6182/$ e see front matter Ó 2010 Elsevier Ltd and INQUA. All rights reserved. doi:10.1016/j.quaint.2010.03.001 Please cite this article in press as: Dimitriu, R.G., Geodynamic and hydro-geological constraints regarding the extension of the prospective..., Quaternary International (2010), doi:10.1016/j.quaint.2010.03.001 ARTICLE IN PRESS 2 R.G. Dimitriu / Quaternary International xxx (2010) 1e11 Fig. 1. Study area (dashed line ellipse) located on the north-western Black Sea coast, in the coastal zone of the Northern Dobruja Region, and the main structural units beneath it (regional geological map after Sandulescu et al., 1978, with modifications). Please cite this article in press as: Dimitriu, R.G., Geodynamic and hydro-geological constraints regarding the extension of the prospective..., Quaternary International (2010), doi:10.1016/j.quaint.2010.03.001 ARTICLE IN PRESS R.G. Dimitriu / Quaternary International xxx (2010) 1e11 3 the formation of the Sfântu Gheorghe I secondary delta, 7000e5200 remains of habitation, settlements and tells) belonging to Prehis- BC; (3) the formation of the Sulina secondary delta, 5200-0 BC, fol- toric times, have only been found on the higher lands that border lowed by its erosion until present; (4) the formation of the Cos¸na- the Danube Delta, along the southern distributary of the River Sinoie secondary delta, 1500 BCe500 AD, and (5) the formation of Danube (i.e. Sfântu Gheorghe branch) at Tulcea, Malcoci, Nufaru the Sfântu Gheorghe II and Chilia secondary deltas, 800 BC- present. and along the western bank of the present-day Razelm-Sinoie As Fig. 2 illustrates, due to the delta lobes’ evolution over time, the lacustrine complex at Sabangia, Sarichioi, Enisala, Tas¸burun Hill, coastline also suffered important displacements with notable Jurilovca, Vis¸ina, Lunca, Sinoie Mound, Istria, Vadu, Corbu and Cape consequences on the number and position of the Danube River’s Midia (Fig. 3). During prehistoric and ancient times, the Razelm- branches discharging mouths and on the related human activities Sinoie area was a gulf of the Black Sea (Halmyris Bay). such as habitation, navigation, and trade. Starting from the 8th century BC, the entire area was dominated According to ancient historians (e.g. Herodotus in the 5th by the presence of the Geto-Dacian population, whose habitation century BC, Polybius in the 2nd century BC, Strabo in the 1st and settlement remains and necropolises were found at Victoria, century BC, Pliny the Elder in the 1st century AD, Ptolemy in the Bes¸tepe, Dunavat¸u along the Sfântu Gheorghe branch and at Eni- 2nd century AD and others), that time, the Danube (Istros) River sala, Tas¸burun Hill, Salcioara, Vis¸ina, Istria, Nuntas¸i and Histria discharged its waters into the Black Sea through five to seven fortress on the western bank of the former Halmyris Bay (Fig. 3). mouths (branches), among which the most important was the Tumular (mound) complexes, probably of Scythian origin and ages Hieron Stoma (Holly Mouth), identified today as being the Sfântu starting with the 6th century BC, are present in the entire study Gheorghe branch of the Danube (Gâs¸tescu and S¸tiuca, 2006). area at Mahmudia, Murighiol, Agighiol, Iazurile, Sarichioi, Salcioara, Jurilovca, Lunca, Baia Dobrogea, Mihai Viteazu, and Corbu. The tumuli complexes and the necropolis found respectively at Chilia 1.2. Archaeological heritage Veche and at Caraorman, of unspecified age, probably the 3rde2nd centuries BC, have special significance due to the presence of the The territory of Dobruja has been inhabited since the Middle Bastarnae tribes within the Danube Delta. and Upper Paleolithic (Radulescu and Bitoleanu, 1979), as the Greek colonization of the Western Black Sea coast, which started remains discovered at Babadag, Enisala, and Gura Dobrogei (Fig. 3), in the 7th century BC at Histria, is responsible for some of the most among other places, certify. During Neolithic time, Dobruja was important archaeological sites found in the study area: the part of the Hamangia, Boian and Karanovo V cultures. Later, at the fortresses of Histria and Argamum (Orgame), the habitation end of the 5th Millennium, the Gumelnit¸a culture occurred in the remains at Tulcea, Murighiol, the fortified settlement at Babadag, region. During Eneolithic time, the cultural blend of local pop- the settlements from Agighiol, Istria, Nuntas¸i, Sacele and the ulation and tribes originating from the northern Black Sea territory necropolises from Baia Dobrogea (formerly named Hamangia) and gave birth to the Cernavoda I to III cultures. Archaeological sites (i.e. Movilele Dese near Histria (Fig. 3). Until now, no archaeological site of Hellenistic origin has been found on the surface of the Danube Delta, except for the transit point for merchandise (5the3rd centuries BC) excavated