Tributary rivers can contribute significantly to alluvial-plain construction by supplying large volumes of clastic material. Their relation to the main axial river strongly influences sediment deposition and preservation. The Po Plain is fed by the Po River and a dense network of transverse tributaries draining the nearby Alpine and Apennine chains. Stratigraphic, sedimentological, petrographic and geochemical analyses on 38 cores permitted detailed differentiation of Po and Apennine sedimentary units. Po River deposits are vertically stacked channel-belt sand bodies with high contents of quartz–feldspar and metamorphic rock fragments, combined with high chromium levels. These sand bodies, 20 to 30 km wide, are replaced southward by finer-grained deposits that represent the distal Apennine tributary-rivers system. Apennine sands, confined in narrow ribbons, show lower quartz–feldspar contents, abundant sedimentary lithics and lower chromium levels. In the last 870 kyr, the boundary between the Po and the Apennine sediment delivery systems shifted along a north–south axis in response to distinct controlling factors. A 20 km northward shift of the Po channel belt, possibly related to a tectonic event, is recorded across a regional unconformity dating to the Marine Isotope Stage 12/11 transition. High sediment supply rates during glacial-lowstand periods widened the Po channel belt southward towards the Apennine domain for a few kilometres. The Last Glacial Maximum channel-belt sand body, 30 km wide and 40 m thick, progressively narrowed northward after the glacial culmination. During the Holocene, channel patterns became avulsive and distributive. Narrow channel belts (<3 km) formed along the Po River branches, and abundant swamp and poorly drained-floodplain muds were preserved in interfluvial areas. Activation and deactivation of the Po branches resulted in sharp narrowing and widening of the area available for Apennine-rivers sedimentation. This work provides insights into tributary-trunk river relations which control grain-size distribution and compositional characters of subsurface deposits.

中文翻译：

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波平原（意大利北部）更新世-全新世地层记录的干河和支流相互作用

支流河流可以通过提供大量碎屑材料对冲积平原建设做出重大贡献。它们与主要轴向河流的关系强烈影响沉积物的沉积和保存。波平原由波河和一个密集的横向支流网络供水，这些支流将附近的阿尔卑斯山和亚平宁山脉排干。对 38 个岩心的地层学、沉积学、岩石学和地球化学分析允许对 Po 和亚平宁沉积单元进行详细区分。坡河矿床是垂直堆积的河道带砂体，石英-长石和变质岩碎片含量高，铬含量高。这些砂体宽 20 至 30 公里，向南被代表亚平宁支流河流系统的细粒沉积物所取代。亚平宁砂，限制在窄带中，显示出较低的石英-长石含量，丰富的沉积岩屑和较低的铬含量。在过去的 870 kyr 中，Po 和亚平宁沉积物输送系统之间的边界沿南北轴移动，以响应不同的控制因素。Po 河道带向北移动 20 公里，可能与构造事件有关，记录在可追溯到海洋同位素阶段 12/11 过渡的区域不整合面。冰川低位时期的高沉积物供应率使 Po 河道带向南向亚平宁域加宽了几公里。末次盛冰期河道带砂体，宽30km，厚40m，在冰期结束后向北逐渐变窄。在全新世期间，通道模式变得令人厌恶且具有分布性。窄槽带 (< 3 公里）沿波河支流形成，在河间地区保留了丰富的沼泽和排水不良的漫滩泥浆。Po 分支的激活和失活导致亚平宁河沉积可用区域急剧变窄和变宽。这项工作提供了对控制地下沉积物粒度分布和组成特征的支流-干河关系的见解。