Abstract The Istria ‘Depression’ or sub-basin of offshore Romania lies at the intersection of the trans-European Tornquist–Teisseyre ‘Zone’ and the Black Sea back-arc basin, just outboard of the East Carpathian orogenic welt. Its Late Mesozoic–Cenozoic succession records an extraordinary polyphase history of subsidence and sedimentation, interrupted by several quite spectacular second-/third-order erosional unconformities, reflecting the interplay between these tectonic domains. The unconformities divide the succession into a number of stratigraphic sequences. The sub-basin first developed as a transtensional rift in the Triassic–Early Jurassic, evolving into a narrow oceanized trough in the later Jurassic. This was tilted west during the Early Cretaceous, and the residual Late Jurassic topography was filled and buried by a west-facing clastic–evaporite wedge. Following Late Aptian–Albian(?) rifting, post-rift subsidence and spreading in the Western Black Sea imposed a strong easterly tilt, encouraging the partial evacuation of its Early Cretaceous sedimentary fill by gravity-driven mass wastage. The incised valley topography was subsequently infilled and buried during the later Cretaceous and Early Cenozoic. During the mid-Late Cenozoic, the Black Sea Basin experienced intermittent periods of partial to complete isolation from the world ocean and significant base-level drawdown. The first major sea-level fall occurred in the Eocene when the Istria ‘Depression’ was deeply incised, to be healed by Oligocene shales during the subsequent rise. Yet another period of drawdown and exposure occurred in the mid-Miocene, with extensive shelf-margin mass wastage and erosion, followed by re-flooding and deposition of a transgressive backstepping sequence in the middle-late Miocene. Messinian drawdown in the Mediterranean caused a further period of isolation and falling base level. The shelf margin was again exposed, and experienced widespread mass wastage and slumping. Rising sea level eroded the earlier slumped sequence and the margin was healed by a lowstand prograding wedge in the late Miocene–early Pliocene. This was followed by shelf sedimentation in the Plio-Pleistocene periodically interrupted by canyon-incision events, testifying to continued climatically or tectonically imposed base-level fluctuations. Several direct and indirect tectonic factors were responsible for valley/canyon incision within the Istria Depression and erosion of the Romanian Black Sea shelf margin. These include: (1) the local structural framework; (2) direct tectonic uplift and tilting; and (3) more indirect tectonically imposed isolation encouraging significant base-level falls.

Abstract One of the main issues in source rock evaluation has always been the availability of thermally immature samples, which would represent the same source rock quality and facies as the mature source rock within the deeper parts of the basin. Forty dropcore sample locations from shallow depths beneath the present-day seafloor were selected and analysed for mineral composition and bulk geochemical parameters. The water depths of the samples range from shelfal to bathyal environments. The quartz content of the samples clearly decreases with increasing distance from sedimentary input sources (e.g. river deltas), whereas clay content increases towards the distal areas. Mass movements (e.g. slides and debris flows) along the present-day shelf are recognizable on the bathymetry, as well as in the mineral content. Bulk geochemical parameters show that currently only poor to fair gas-prone source rocks are deposited within the study area. This lack of source rock quality, as well as organic content, is attributed to the fine-grained sedimentary input from the Danube river. These fine-grained sediments decrease the organic productivity due to dulling (decrease in the thickness of the photic zone) of the water column, and dilute the currently deposited source rock with low TOC sediments. These effects decrease with distance from the Danube delta, as indicated by published data from outside the study area. Additionally mass movements along the present-day shelf rework possible source rocks. The results of this study clearly show that anoxic conditions alone are not sufficient for source rock deposition. Distance from major sedimentary input and basin geometry are of major importance, and should be considered in basin modelling.

Abstract Loess is wind-blown sediment that covers extensive areas in the middle latitudes. Much of the loess in Eastern and Central–Eastern Europe has been redeposited by the River Danube and its tributaries. The case study area (Vojvodina region) encompasses the confluence area of the Danube, Sava and Tisa rivers. This region includes the most complete and the thickest loess–palaeosol sequences found in Europe, a valuable record of palaeo-climates over the past two million years only recognized in the closing decades of the twentieth century. Long before then however, several enthusiasts, engineers and travellers recognized and appreciated loess as a significant natural phenomenon. Among them was Luigi Ferdinando Marsigli (1658–1730) who gave the first scientific description of European loess in his outstanding multivolume work Danubius Pannonico Mysicus where he drew and explained notable loess–palaeosol exposures along the Danube River. Many other loess observations were also recorded by a number of international travellers, whose illustrated travelogues (mainly published in the nineteenth century) mentioned and illustrated loess observations along the Danube and its major tributaries. This chapter explores the interplay of scientific loess research and its geo-historical literary aspects as the foundations of modern loess geotourism.

Abstract Despite having at least one major river, the Danube, supplying sediment to the Black Sea, the presence of significant deep-water clastic reservoirs has always been viewed as the major exploration risk. Source to sink concepts have been used examine this risk. Reconstruction of plausible paleodrainage scenarios combined with knowledge of the paleogeography, climate and hinterland geology have been used to estimate paleosediment budgets and provide an assessment of reservoir quality in the basin. Analysis of the basin fill, interpreted from extensive seismic coverage calibrated by wells, allows further refinement of the rates of sediment supply. A forward model of the basin fill has been created that successfully produces a postulated fill matching the observed geometry of the fill of the basin. Our analysis shows that fluvial drainage into the Black Sea from the Oligocene through to the Pleistocene has been dominated by small, local, mountainous hinterland drainage, formed in the many surrounding orogens and volcanic arcs. The resulting sediment supplied is predicted to be of low quality. Likely routes for large long-lived fluvial systems draining the continental shields to the north and west, include many updip sediment-trapping basins on the way to the Black Sea, suggests that sediment entered the basin in volume only in the latest Pleistocene. Therefore the risk of finding large volumes of sandstone in the form of large pre-Pleistocene deep-water fan complexes is high. However, smaller volume locallysourced fan-aprons may be common throughout the pre-Pleistocene succession around the margins of the basin.

Abstract The Danube River Basin and the Black Sea represent a unique natural laboratory for studying source to sink and global change. We will address information on the “active sink” of the system, which represents the area of active deposition: sea level variation, sediment balance, and neotectonics. Also, we will discuss the evolution and quantification of climate, tectonics, and eustasy on the sedimentation in the western Black Sea basin, along both southern and northern margins, obtained from understanding the Danube deep-sea fan processes and sedimentation. In the last decade, many of the geosciences studies carried out in the Black Sea have focused on the Holocene marine transgression. This topic has been fully discussed and is still a matter of debate. Since the DSDP drillings, the lithology and mineralogy of deep sediments from the Black Sea have been well studied. However, only few recent studies have focused on the deep-sea morphology and turbidite sedimentation in the western Black Sea basin, in which the main depositional feature is the Danube submarine fan. Oceanographic surveys in the Black Sea in 1998, 2002, and 2004 carried out in the framework of French-Romanian joint project and the European ASSEM-BLAGE (EVK3-CT-2002-00090) project have collected a large amount of data (Multibeam echo sounder data, CHIRP seismic, as well as Kullenberg and Calypso cores). This paper presents insights from recent coring and seismic data recovered at the boundary of influence of both the distal part of the Danube turbiditic system and the Turkish margin. This data set provides a good record of changes in the sedimentary supply and climatic changes in the surrounding Black Sea since the last 25 ka. Based on this study, we demonstrate that the deep basin deposits bear the record of the late Quaternary paleoenvironmental changes. Finally, the western Black Sea basin constitutes an asymmetric subsident basin bordered by a northern passive margin containing confined mid-size, mud-rich turbiditic systems, and a tectonically active southern turbiditic ramp margin.

This paper presents geophysical and core data obtained from several marine geology surveys carried out in the western Black Sea. These data provide a solid record of water-level fluctuation during the Last Glacial Maximum in the Black Sea. A Last Glacial Maximum lowstand wedge evidenced at the shelf edge in Romania, Bulgaria, and Turkey represents the starting point of this record. Then, a first transgressive system is identified as the Danube prodelta built under ~40 m of water depth. The related rise in water level is interpreted to have been caused by an increase in water provided to the Black Sea by the melting of the ice after 18,000 yr B.P., drained by the largest European rivers (Danube, Dnieper, Dniester). Subsequently, the Black Sea lacustrine shelf deposits formed a significant basinward-prograding wedge system, interpreted as forced regression system tracts. On top of these prograding sequences, there is a set of sand dunes that delineates a wave-cut terrace-like feature around the isobath −100 m. The upper part of the last prograding sequence is incised by anastomosed channels that end in the Danube (Viteaz) canyon, which are also built on the lacustrine prograding wedge. Overlying this succession, there is a shelfwide unconformity visible in very high-resolution seismic-reflection profiles and present all over the shelf. A uniform drape of marine sediment above the unconformity is present all over the continental shelf with practically the same thickness over nearby elevations and depressions. This mud drape represents the last stage of the Black Sea water-level fluctuation and is set after the reconnection of this basin with the Mediterranean Sea.