Fluvial deposits subjected to this study are exposed at the Brześnica site, in the south-western part of the Wielkopolska region in Poland, which was close to the ice-sheet limit during the Last Glacial Maximum (LGM). Sedimentological analyses, including lithofacies descriptions, palaeocurrent measurements, grain size and rounding analyses and heavy mineral compositions indicate that the fluvial deposits at Brześnica were deposited in braided river environment. The following fluvial sedimentary processes were inferred: (1) shallow, rapid flow alternating with waning flow, (2) infilling of erosional channels with fluvial sediments during flood events, (3) changes from supercritical to subcritical flows, and (4) shallow sheet floods. The results of OSL dating indicated sediment deposition ~65.2 ±1.5 ka, i.e. in MIS 4, that was here characterized by cold environmental conditions and a general shift from meandering to braided fluvial sedimentation style. This finding contrasts with accumulation/erosion phases interpreted previously in this region for that time interval; however, it is consistent with recent studies of fluvial systems functioning during MIS 5-2 and of factors responsible for sedimentation style.

中文翻译：

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MIS 4-3 期间对环境条件的河流响应：波兰中西部 Brześnica 遗址的沉积记录

受本研究影响的河流沉积物暴露在位于波兰 Wielkopolska 地区西南部的 Brześnica 遗址，该遗址在末次盛冰期 (LGM) 期间接近冰盖极限。沉积学分析，包括岩相描述、古流测量、粒度和圆角分析以及重矿物成分，表明布热尼察的河流沉积物沉积在辫状河环境中。推断出以下河流沉积过程：(1) 浅层快速流与减弱流交替，(2) 在洪水事件期间用河流沉积物充填侵蚀通道，(3) 从超临界流变为亚临界流，以及 (4) 浅表洪水。OSL 测年结果表明沉积物沉积 ~65.2 ±1.5 ka，即在 MIS 4 中，这里的特点是寒冷的环境条件和从蜿蜒到辫状河流沉积方式的普遍转变。这一发现与先前在该地区在该时间间隔内解释的积累/​​侵蚀阶段形成对比；然而，它与最近对 MIS 5-2 期间河流系统功能的研究以及对沉积方式负责的因素的研究是一致的。