Two Late Pleistocene climate-driven incision/aggradation rhythms in the middle Dnieper River basin, west-central Russian Plain

Andrei Panin, Grzegorz Adamiec, Jan-Pieter Buylaert, Ekaterina Matlakhova, Piotr Moska, Elena Novenko

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    Abstract

    In valleys of the River Seim and its tributaries in the middle Dnieper basin (west-central Russian Plain), two low terraces (T1, 10-16 m, and T0, 5-7 m above the river) and a floodplain (2-4 m) with characteristic large and small palaeochannels exist. A range of field and laboratory techniques was applied and _30 new numerical ages (OSL and 14C dates) were obtained to establish a chronology of incision and aggradation events that resulted in the current valley morphology. Two full incision/aggradation rhythms and one additional aggradation phase from the previous rhythm were recognized in the Late Pleistocene - Holocene climate cycle. The following events were detected. (1) Late MIS 5 - early MIS 4: aggradation of Terrace T1 following the deep incision at the end of MIS 6. (2) Late MIS 4 (40-30 ka): incision into Terrace T1 below the present-day river, formation of the main scarp in the bottom of the valley between Terrace T1 and Terrace T0/Floodplain levels. (3) MIS 2: aggradation of Terrace T0, lateral migrations of a shallow braided channel located few meters above the present-day river since ∼25 ka through the LGM. (4) 18-13 ka: incision into Terrace T0 below the modern river. Multiple-thread channels concentrated in a single flow that at some places formed large meanders. In the period 15-13 ka, high floods that rose above the present-day floods left large levees and overbank loams on Terrace T0. (5) Younger Dryas - Holocene transition: aggradation up to the modern channel level, transformation of large Late Glacial to small Holocene meanders. The established incision/aggradation rhythms are believed to be manifested over the Central Russian Plain outside the influence of ice sheets in the north and base level changes in the south.The two-phase deepening of the valley occurred in the last quarter of the last glacial epoch but can not be attributed directly to the glacial-interglacial transition. Both the detected incision events correspond to relatively warm climate phases - late MIS 3, post-LGM warming including the Bølling-Allerød interstadial. Anomalously large size of the preserved river palaeochannels prove that the post-LGM incision phase was induced by a climatically forced large increase of water runoff. Considerable increase of water discharges is considered the most probably cause for the late MIS 4 incision phase also. Therefore river incision seems to have been governed rather by changing water runoff that oscillated in phase shift with the thermal regime.
    Original languageEnglish
    JournalQuaternary Science Reviews
    Volume166
    Pages (from-to)266-288
    Number of pages23
    ISSN0277-3791
    DOIs
    Publication statusPublished - 2017

    Keywords

    • Aeolian processes
    • Fluvial geomorphology
    • Large meanders
    • OSL dating
    • Palaeochannels
    • River palaeohydrology
    • River terraces
    • SEM study of quartz grains

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