Revealing inherited Precambrian crustal structure of the Vaupés Arch in the Colombian Amazonian Craton using teleseismic receiver functions and gravity spectral analysis

Uncovering the crustal structure is essential for understanding the tectonic history of a region. However, such analysis in remote and poorly exposed areas such as the Colombian Amazonian Craton is often challenging due to limited geological and geophysical data. This research presents a new regional Moho model for the southeastern Amazonian region in Colombia, encompassing the Sub-Andean basins and part of the northwestern Amazonian Craton. We combined Moho depth estimates from gravity analysis, using a 2D radially averaged power spectrum, with those derived from receiver functions using the H-k stacking technique at five seismic stations. The resulting Moho map reveals notable crustal heterogeneities along the NW-SE trending Vaupés Arch, with depths ranging from 33 to 51 km. In the light of the limited evidence of Phanerozoic tectonic activity in the Colombian Amazonian Craton and the inconsistency between Moho depths and present-day topography as indicated by an isostatic model, we suggest that the observed Moho depth variations likely reflect a polyphase history of Precambrian contraction and extension in the NW Amazonian Craton. This history is linked to Neoproterozoic rifting during Rodinia’s break-up, which led to discontinuous crustal thinning in crustal domains previously thickened by Paleo-Mesoproterozoic orogenic pulses and the compressional phases of the Putumayo Orogen. Our findings underscore the value of integrating geophysical methods to better understand the tectonic evolution of cratonic regions with sparse surface data.

揭示地壳结构是理解区域构造演化历史的核心前提。然而，在哥伦比亚亚马逊克拉通（Colombian Amazonian Craton）这类偏远且出露条件不佳的区域开展相关研究，往往因地质与地球物理数据匮乏而面临极大挑战。本研究针对哥伦比亚东南部亚马逊区域（涵盖亚安第斯盆地与西北亚马逊克拉通的部分区域）构建了一套全新的区域莫霍界面（Moho）模型，将基于二维径向平均功率谱的重力分析所得的莫霍深度估算结果，与5个地震台站处采用H-k叠加技术得到的接收函数（receiver functions）反演结果进行融合。所生成的莫霍界面分布图显示，沿北西-南东走向的瓦佩斯穹窿（Vaupés Arch）存在显著的地壳非均质性，莫霍深度介于33至51千米之间。鉴于哥伦比亚亚马逊克拉通显生宙（Phanerozoic）构造活动证据有限，且均衡模型显示莫霍深度与现今地形之间存在不一致性，我们认为观测到的莫霍深度变化大概率反映了西北亚马逊克拉通前寒武纪（Precambrian）多期挤压与伸展的演化历史；该演化历史与罗迪尼亚超大陆裂解时期的新元古代（Neoproterozoic）张裂作用相关，这一作用导致此前被古-中元古代造山脉冲以及普图马约造山带（Putumayo Orogen）挤压阶段增厚的地壳区域出现了不连续的地壳减薄。本研究结果凸显了整合多种地球物理方法的重要价值，可为地表数据匮乏的克拉通区域构造演化研究提供更为深入的认知。