PALEOTEMPESTOLOGICAL RESEARCH ALONG THE BESSARABIAN LIMAN COAST OF THE BLACK SEA, UKRAINE

The northwestern coast of the Black Sea is ideal for paleotempestological research due to: 1) relatively stable margin with infrequent tsunami impact (no reports during AD 600-1800) compared to other parts of the basin; 2) presence of accumulation forms that prograded during the past 4-5 ky; 3) non-tidal basin, which minimizes wave run-up elevation errors; 4) presence of heavy minerals in sand fraction that can serve as density-lag event horizons; 5) abundance of datable organic materials (gastropods and articulated Mytilus, Cardium, and Chione bivalves), and 6) long-term occupation of the coastal area, which left documentary records of high-magnitude events and useful chronostratigraphic markers. Field research at five sites along the coast of Ukraine (Odessa region), employed high-resolution 800 MHz MALÅ ground-penetrating radar (GPR) imaging and trenching of prograded beach-ridge complexes (Albatross strandplain, Sasyk-Kunduk barrier) and retrograding barriers fronting Bessarabian limans (drowned fluvial paleo-valleys). Subsurface records reveal sharp offlaping reflections interpreted as erosional paleo-scarps. Garnet-enriched layers yielded a bulk low-field magnetic susceptibility of >1,700 μSI, compared to -40 to +30 μSI for the background mixed quartzose-carbonate beach and dune sands. The preservation of geological signatures of punctuated progradation is insured in areas of net accretion. Over a longer term, a SL-modulated rise in water table will aid in the detection and spatial discrimination of paleo-erosion indicators due to increased resolution of GPR signal in saturated media. The resulting regional database will provide a means of addressing the challenges of differentiating between coastal-morphological changes forced by fluctuations in sea level (SL) and those produced by storm surges. Indicative mollusks in paleo-storm horizons date back more than 1,200 years, with optical dating of overlying berm and aeolian accretion facies underway to complement the radiocarbon chronology. The refined timeline of late Holocene storm events will ultimately provide a framework for evaluating the links between the North Atlantic climatic shifts and basin-scale oceanographic dynamics within the Pontic region.