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The present paper synthesizes the evolution of fluvial systems tributary to the Black Sea (within 25 – 8 ka BP time frame) by reviewing the existing paleoclimate, hydro-geomorphology, sedimentology and Late Quaternary chronology. These studies are unevenly distributed throughout the Black Sea (BS) drainage basin and were used to decipher the river response to climatic, eustatic, tectonically induced or vegetation cover changes. The river response was sensitive overall and is visible particularly in terms of the channel planform. The alternation of cold and warm climate phases has controlled to a significant degree the water and sediment inputs along the drainage networks, such that river channels planforms shifted from the braided type to the anastomosed type (with various transitional phases, either wandering or anastomosed), and from macro-meanders to small scale meanders. The climatic model of fluvial evolution was altered by the other controlling factors specific to the large BS drainage basin, including tectonics (in the Pannonian Plain, Western Plain of Romania, Lower Siret Plain), the proximity to coarse-grained sediment sources (typical for medium-sized Carpathian tributaries), the obstruction exerted by glacial sediments generated by the ice cap retreat (as illustrated on the Upper Dnieper), eustatic oscillations (detected on the Danube or Sakarya River). The sea level drop by more than 100 m during the Last Glacial Maximum resulted in the conversion of ca. 30% of the present sea surface to dry land (mostly on the NW continental shelf); several sinuous-anastomosed paleo-channels pertaining to major rivers (Danube, Dniester, Dnieper) with depths ranging between 30 and 90 m were reconstructed on the surface of this emerged land. Black Sea became connected to the Planetary Ocean during the Early Holocene (ca. 9.4 ka BP). The sea waters flooded extensive areas at the NW and advanced upstream along tributary river valleys. The effects of base level rise were reflected in the anastomosed style of river channels and the accumulation of deltaic formations.

Omagiu unui prieten / Tribute to a friend - Virgil Surdeanu (1946 - 2018)

This paper focused on the analysis of the interpretation potential given by fluvial archives, in order to decipher the Mid- to Late Holocene sedimentary history. The database discussed here refers to 65 dated ages (mostly radiocarbon), mappings of the most representative floodplain reaches of Suceava, Moldova and Siret rivers, and 23 outcrops analysed in floodplain deposits (river banks or gravel pits). The study results concentrated on (a) describing the regional features of Eastern Carpathian floodplains, (b) the floodplain morphology and its correlation with the structure of fluvial deposits and (c) identifying the paleoevents of fluvial activity on a centennial timescale. In this way, we were able to identify a general pattern of the dynamic geomorphology history for the rivers situated eastward of the Carpathians, which resulted from combining the Mid- to Late Holocene sedimentation phases, the avulsion and lateral migration processes that occurred during high fluvial activity intervals and the morphological adjustment of the rivers channels, from braiding to wandering and sinuously–meandering. The chronological overlay of the events revealed that the time intervals with the most extensive fluvial processes on the rivers draining the Eastern Carpathians occurred (in years before present) during 6200, 5300, 4100–4080, 3600, 2300–2200 (Iron Age), 1300 (Migrations Period), 950–970 (Medieval Climate Anomaly), 750–520 BP (Little Ice Age) and that these intervals generally overlap the high precipitation palaeoclimatic episodes documented in Romania. The fluvial activity of the rivers during the Mid- to Late Holocene has been compared as well with several records of paleo–climates variability over the geographical area of Romania. The result showed that many flooding episodes were coincident with the wet and cold intervals which were also identified in the variation of the other proxy data, especially after 4.7 kcal BP.

Our present work is meant to discuss the dynamics in sorne cross-sections of severa! rivers situated in different conditions: discharge and load, grain size channel deposits, slope, channel pattern, anthropic intervention. For the short intervals of time characteristics for high floods and season cycles, there has been noticed an alternation of "fill" and "scour" on an amplitude which may go beyond 1-1,5 m. For the longer intervals of time (years) we noticed the alternation of the aggradation and degradation phenomena with a maximal amplitude up to 2-3 m. and even more. We also evaluated the conditions of morphplogical stability of the channels, obtaining exponents of the discharge-at a station with a relatively large space of variation.

Landform dynamics and evolution in Romania Rădoane, Maria, Vespremeanu-Stroe, Alfred – Editors Springer International Publishing Switzerland, 2016, 867 p. ISBN 978-3-319-32589-7 Library of Congress Control Number: 2016942904 DOI 10.1007/978-3-319-32589-7