Abstract Neotectonic reactivation has been increasingly documented in many areas of the Amazonian lowlands, but the evidence has been only for extensional structures. This work investigates a large-scale sinusoidal-shaped morphology (Ssm) in a relief dominated by late Quaternary deposits in the north of the Solimoes Basin. The digital elevation model (DEM) of the shuttle radar topography mission (SRTM) was used as a basis to characterize this structure and improve the knowledge of its geological context. The Ssm is a Z-shaped sinusoid with a wavelength of approximately 135 km, formed by two merged asymmetrical curves. The north curve has an amplitude of 70 km and a core topographically lower and geologically younger than the limbs, while the south curve has an amplitude of 90 km and a core with older geological units and higher relief than the limbs. A main NE-striking morphostructural lineament has horizontally displaced the rocks near the axial plane in the north curve. Also described are several NW-trending lineaments that laterally displaced the modern and ancient valley segments. Our morphological data led to the hypothesis that the Ssm north and south curves could record a plunged syncline and an anticline, respectively, and that the laterally displaced lineaments are strike-slip faults. Although this type of fault has already been described in the region, the propagation of folds in the Pleistocene-Holocene deposits is a new finding. Assuming this model, the SW- to WSW-plunging folds would suggest a main NW- to WNW-oriented maximum horizontal compression activated contemporaneously or shortly after the Pleistocene-Holocene deposition. This proposed orientation for the stress field is interesting because it would reveal a rotation, in this region, of the main E-W stress field recorded for South America. On the other hand, the suggested NW to WNW-oriented compression is compatible with the models based on earthquake focal mechanisms comparing data from Brazil and the sub-Andean region. As such, the present work can bring new insights to discuss the impact of the late stage displacement of the South American plate in an intraplate region away from the passive margin, although the contribution of local stresses must be also considered.

中文翻译：

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亚马逊低地是否证明了晚更新世-全新世压缩？

摘要 在亚马逊低地的许多地区，新构造再激活的记录越来越多，但证据仅适用于伸展结构。这项工作调查了在索利莫斯盆地北部以晚第四纪沉积物为主的地貌中的大规模正弦形形态 (Ssm)。航天飞机雷达地形任务 (SRTM) 的数字高程模型 (DEM) 被用作表征该结构并提高对其地质背景知识的基础。Ssm 是一个波长约为 135 公里的 Z 形正弦曲线，由两条合并的不对称曲线形成。北曲线的振幅为 70 公里，核心在地形上低于四肢，地质上年轻，而南曲线的振幅为 90 公里，岩心具有较旧的地质单元，且地势高于四肢。一个主要的 NE 走向的形态构造线在北曲线的轴平面附近水平移动了岩石。还描述了几个 NW 趋势的线条，它们横向移动了现代和古代的山谷段。我们的形态数据导致假设 Ssm 北曲线和南曲线可以分别记录下倾的向斜和背斜，并且横向位移的线状体是走滑断层。尽管该地区已经描述了这种类型的断层，但在更新世-全新世沉积物中褶皱的扩展是一个新发现。假设这个模型，SW 到 WSW 的俯冲褶皱表明主要的 NW 到 WNW 方向的最大水平压缩在更新世 - 全新世沉积的同时或不久激活。这个应力场的建议方向很有趣，因为它会揭示南美洲记录的主要 EW 应力场在该区域的旋转。另一方面，建议的 NW 到 WNW 导向的压缩与基于地震震源机制比较巴西和亚安第斯地区数据的模型兼容。因此，目前的工作可以带来新的见解来讨论南美板块在远离被动边缘的板内区域后期位移的影响，尽管也必须考虑局部应力的贡献。