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

机译：两个晚熟气候驱动的切口/俄罗斯西部中罗宾河流域中河流河流域的委员会节奏

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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.
机译：在Seim河的山谷及其支流中的中间Dniep​​er盆地（俄罗斯州西部平原），两个低露台（T1,10-16米和T0，河上5-7米）和洪泛区（2- 4米）存在特征大和小古希腊菜。应用了一系列现场和实验室技术，并获得了_30新的数值年龄（OSL和14C日期），以建立所导致当前谷形态的切口和加重事件的年代学。两个完全切口/委员会的节奏和前一节奏的一个额外的汇聚阶段被认可在晚熟 - 全新世气候循环中。检测到以下事件。 （1）迟到的MIS 5 - 早期MIS 4：MIS末期深入切口后的露台T1的侵略性6.（2）晚期MIS 4（40-30 kA）：切口进入当天河下方的露台T1，在露台T1和露台T0 /泛洪平均水平之间形成山谷底部的主围巾。 （3）MIS 2：露台T0的纺织，浅层偏移，浅编织频道，位于当今河流以上的几米之上，自LGM 25 ka以来。 （4）18-13 KA：切入现代河下方的露台T0。多螺纹通道集中在一个流动的单一流动中，在某些地方形成了大蜿蜒。在15-13 ka的时间内，高于现日洪水的高洪水落在露台T0上的大型堤坝和超壁壤土。 （5）较年轻的Dryas - 全新世过渡：对现代渠道水平的收入，大型晚期冰川转变为小全新世蜿蜒。既定的切口/委员会的节奏被认为是在南方冰片和基地变化中的冰层的影响之外表现在中央俄罗斯平原上。谷的两阶段深化在最后一个冰川的最后一个季度发生时代，但不能直接归因于冰川层面过渡。检测到的切口事件都对应于相对温暖的气候阶段 - 晚期MIS 3，LGM后温暖，包括Bølling-Allerød壁龛。通常大尺寸的保存河古社会证明了后LGM切割阶段被气候迫使促进水径流诱导。相当大的排水量被认为是最迟到的MIS 4切割阶段的原因。因此，河道切口似乎已经受到了改变振荡的水径流与热量制度的偏振。

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