Abstract Tafoni and honeycombs remain some of the most enigmatic and puzzling geomorphological phenomena. Their globally widespread occurrence across a wide range of lithologies and environmental conditions suggests that their formation is determined by a factor that overarches variations in these conditions and weathering processes. Based on a study of tafoni and honeycombs in the Crimean Piedmont, this paper demonstrates that the primary factor in their formation is the pre-exposure alteration of rocks along fractures and karst conduits as a result of fluid–rock interactions. Such alteration is commonly induced by ascending flow and is related to hypogene karstification. The morphological expression of cavernous features through removal of the alterite can occur under subsurface conditions, but is more frequent on exposure to atmospheric weathering. The local or regional characteristics of a weathering system are irrelevant or of only secondary importance in determining the localization and morphology of cavernous features. New features do not form on rock surfaces where the alteration zone was totally denuded or never present. The proposed model resolves major issues inherent to previous interpretations of cavernous features. It has general applicability and important implications for geodynamic and palaeohydrogeological reconstructions. Typical tafoni and honeycombs may indicate past events of ascending flow and the potential presence of hypogene karst systems.

Abstract Oligocene and Lower Miocene deposits in the Paratethys are important source rocks, but reveal major stratigraphic and regional differences. As a consequence of the first Paratethys isolation, source rocks with very good oil potential accumulated during Early Oligocene time in the Central Paratethys. Coeval source rocks in the Eastern Paratethys are characterized by a lower source potential. With the exception of the Carpathian Basin and the eastern Kura Basin, the source potential of Upper Oligocene and Lower Miocene units is low. In general, this is also valid for rocks formed during the second (Kozakhurian) isolation of the Eastern Paratethys. However, upwelling along a shelf-break canyon caused deposition of prolific diatomaceous source rocks in the western Black Sea. Overall, Oligocene–Lower Miocene sediments in the Carpathian Basin (Menilite Formation) can generate up to 10 t HC m −2 . Its high petroleum potential is a consequence of the interplay of very high productivity of siliceous organisms and excellent preservation in a deep silled basin. In contrast, the petroleum potential of Oligocene–Lower Miocene (Maikopian) sediments in the Eastern Paratethys is surprisingly low (often <2 t HC m −2 ). It is, therefore, questionable whether these sediments are the only source rocks in the Eastern Paratethys.

Pollen and lithopedological data were obtained from Upper Paleolithic sites and Upper Pleistocene loess-soil sequences located between the Sea of Azov and the River Donets, and in the foothills of the Crimean Mountains. During the last Middle Pleniglacial interstadial (Upper Vytachiv soil, 30–27 ka), there existed boreal steppe (south-boreal forest-steppe in Crimea). During the Late Pleniglacial, two main phases of loess accumulation occurred, which were separated by the phase of initial pedogenesis. The loess accumulated under subperiglacial xeric steppe (particularly dry at 15–13 ka), and the incipient soils (Dofinivka unit, 18–15 ka) formed under boreal grassland. During the Late Glacial interstadials, there existed boreal and south-boreal forest-steppe with a relatively wet climate (middle Prychernomorsk soil unit, the upper soil 11.8–11.4 ka). During the Younger Dryas, grassland reappeared under a dry and cool climate (10.9–10.5 ka). Paleoclimatic changes demonstrate the same pattern in both studied areas, and they correspond well with Black Sea transgressive-regressive cycles. Regional differences still existed—during all phases, the climate was the mildest in the western foothills of the Crimean Mountains, the coldest in the Donetsk Upland, and the driest near the Sea of Azov.

We discuss pollen, soil, geomorphologic, and archaeological records used for reconstructing climatic, biogeographic, and human-environment events in the Crimean Peninsula during the past 130 k.y. Warm and moist conditions conducive to forest growth prevailed during the Eemian Interglacial (marine isotope stage [MIS] 5e). Although sea levels were higher than at present, a review of the stratigraphic and geomorphic data suggests that the peninsula was not detached from the mainland. During the last glacial period (MIS 5d–MIS 2), conditions fluctuated between steppe and tree growth in warmer places during the stadials, and forest-steppe during the interstadials. The Pleistocene–Holocene transition involved forest growth during the Bølling-Allerød interstadials, steppe during the Younger Dryas, and a forest-steppe during the early Holocene. The establishment of the modern Black Sea ca. 7 ka and increasing temperatures led to the formation of the modern vegetation belts, ushering in optimal conditions for the establishment of Neolithic communities. A dry period peaked around 4–3.5 ka, followed by milder conditions that lasted until the colonization of Crimea by Greek farmers during the middle part of the first millennium A.D. Dry conditions at the end of the same millennium led to the abandonment of agriculture and settlement decline. Sea-level oscillations during the late Holocene had an important effect on shoreline configuration, lagoonal systems, coastal wetlands, and human settlements. Data used in this paper were drawn from a number of published papers, mostly in Russian and Ukrainian, as well as records produced by the authors' research.

The Black Sea basin presents an ideal laboratory for investigations of morphodynamic interplay between response (morphology) and force (processes) associated with shelf sedimentation. Recent studies along the perimeter of the basin have documented the existence of a complex, heterogeneous seafloor varyingly composed of sand, gravel, silt, and clay. Side-scan sonar data are utilized to establish the spatial patterns of bedform types in the area. In addition, a benthic tripod, configured with an acoustic Doppler current profiler, a rotary fanbeam sonar, and a conductivity-temperature sensor was deployed to record seabed dynamics in response to changing forcing conditions. Together, the tripod and side-scan survey data sets provide a complementary basis for deciphering the processes responsible for the observed seafloor morphology. The side-scan sonar data allows for the determination of spatial patterns of bedform length and orientation. In total, 2376 individual large sand wave bedforms were digitized in geographic information systems with mean and modal wavelengths of 72.8 and 15.7 m respectively. The correlation of near-inertial waves (velocity amplitude 12–20 cm/s and period 12–16 h) and bedform geometry suggest that the extensive sand-wave patches imaged across the shelf are affected by active modern processes and may themselves be modern features or perhaps relict features that remain active presently. Progressive vector diagrams of the nearbed mean current flow indicate a component of cross-shelf directed flow, suggesting an enhanced potential for artifact preservation via cross-shelf advection of anoxic bottom waters by the near-inertial flows measured in this study.