Abstract Three levels of Pleistocene-Holocene fluvial terraces, informally referred to as Upper (UT), Intermediate (IT) and Lower (LT) Terraces, are described in the stretch between the Purus and Manacapuru tributaries (Western Amazonia) of the Solimoes-Amazonas river system, using remote sensing, sedimentological, stratigraphic and geochronological data. The terrace levels are located at heights between 15 and 75 m, defining bands parallel and symmetrical to the channel system that extends for tens of kilometers, truncated by paleochannel features. Internally, the intercalations of sand and mud (silt and clay) layers form the Inclined Heterolithic Stratification (IHS) pairs that are related to the migration of scrollbars, with ages from 204 to 0.75 ka determined by Optically Stimulated Luminescence (OSL). In this period, the low stability of the channel system was related to the meandering fluvial pattern that originated an extensive alluvial plain area, with symmetrical fluvial terraces levels, consisting of point bars with IHS and paleochannel features. However, multi-temporal data analysis of the last decades shows that the Solimoes-Amazonas river system has a high degree of stability, indicated by the low migration rate of the channels, and the presence of muddy and phytostabilized islands and marginal bars that define the current anastomosed-anabranching pattern. The time involved in changing the river pattern and the associated processes has been a source of controversy. Geomorphological, current sedimentary and stratigraphic data indicate that the change occurred in the Pleistocene - Holocene transition, probably due to the paleoclimatic, tectonic and glacio-eustatic changes that affected the sea level rise (North Atlantic), consequently, decreasing the gradient and increasing the sedimentary input that, associated with the increasing humidity (forest vegetation), made the channel system more stable.

中文翻译：

---

Solimões-Amazonas河流系统的更新世-全新世沉积矿床，西亚马逊

摘要 三个层次的更新世-全新世河流阶地，非正式地称为上 (UT)、中 (IT) 和下 (LT) 阶地，描述在 Solimoes-Amazonas 的 Purus 和 Manacapuru 支流（西部亚马逊河）之间河流系统，使用遥感、沉积学、地层学和地质年代学数据。阶地层位于 15 到 75 m 之间的高度，定义了与延伸数十公里的通道系统平行和对称的带，被古通道特征截断。在内部，砂和泥（粉砂和粘土）层的夹层形成了与滚动条迁移相关的倾斜异石分层（IHS）对，其年龄从 204 到 0.75 ka，由光激发光（OSL）确定。在这个时期，河道系统的低稳定性与蜿蜒的河流模式有关，该模式起源于广阔的冲积平原区，具有对称的河流阶地，由具有 IHS 和古河道特征的点状坝组成。然而，过去几十年的多时相数据分析表明，索利莫斯-亚马逊河系统具有高度的稳定性，表现为通道的低迁移率，以及泥泞和植物稳定的岛屿和边缘酒吧的存在。当前吻合 - 分枝模式。改变河流格局和相关过程所涉及的时间一直是争议的根源。地貌、现今沉积和地层资料表明，变化发生在更新世—全新世过渡时期，可能是由于古气候、