Clastic deposition, provenance, and sequence of Andean thrusting in the frontal Eastern Cordillera and Llanos foreland basin of Colombia
Clastic deposition, provenance, and sequence of Andean thrusting in the frontal Eastern Cordillera and Llanos foreland basin of Colombia
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DOI：
10.1130/b30412.1
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发表时间：
2012-01-01
影响因子：
4.9
通讯作者：
Stockli, Daniel F.
中科院分区：
文献类型：
--
作者：
Bande, Alejandro;Horton, Brian K.;Stockli, Daniel F.
北方安第斯山脉（北纬6度）现代变形前缘盆地充填物的沉积学、物源和碎屑热年代学结果提供了沿着东科迪勒拉山脉的前陆-盆地沉积作用的长期始新世至上新世记录！哥伦比亚的Janos盆地边界。在努吉亚向斜向上变粗、厚达5公里的序列中，岩相组合和古水流方向揭示了从克拉通源浅海远源前陆系统性的转变米拉多组（后隆）堆积，到造山源、三角洲和海岸影响的远中前陆沉积（前渊），到下瓜亚博组和上瓜亚博组近端前陆（前渊至楔形顶部）盆地的网状河流和分布辫状河流巨扇系统。沉积过程和沉积物扩散的这些变化的支持下，在碎屑锆石U-Pb和（U-Th）/He年龄，记录折返的不断发展，划分的沉积物源区在东科迪勒拉的上段变化。这些数据被解释为褶皱-逆冲变形的向东推进，在Floresta盆地西缘沿着东科迪勒拉的轴向地带有晚始新世-渐新世变形（Soapaga逆冲断层），早中新世复活中生代裂谷系东缘（反转）（Pajarito和Guaelamamo推力），中、晚中新世下盘短断层的扩展（Vopal逆冲断层），它在东部山麓沿着从东科迪勒拉到哈姆斯前陆盆地的过渡地带的楔顶（背驮式）环境中形成了Nunchia向斜。总的来说，这里提供的数据为前东科迪勒拉定义了一个一般的顺序模式的向东推进褶皱和逆冲变形在新生代东西缩短在哥伦比亚安第斯山脉。
Sedimentological, provenance, and detrital thermochronological results for basin fill at the modern deformation front of the northern Andes (6 degrees N latitude) provide a long-term, Eocene to Pliocene record of foreland-basin sedimentation along the Eastern Cordillera !Janos basin boundary in Colombia. Lithofacies assemblages and paleocurrent orientations in the upward-coarsening, 5-km-thick succession of the Nunchia syncline reveal a systematic shift from craton-derived, shallow-marine distal foreland (back-bulge) accumulation in the Mirador Formation, to orogen-sourced, deltaic, and coastalinfluenced sedimentation of the distal to medial foreland (foredeep) in the Carbonera and Leon Formations, to anastomosing fluvial and distributive braided fluvial megafan systems of the proximal foreland (foredeep to wedge-top) basin in the lower and upper Guayabo Formation. These changes in depositional processes and sediment dispersal are supported by up-section variations in detrital zircon U-Pb and (U-Th)/He ages that record exhumation of evolving, compartmentalized sediment source areas in the Eastern Cordillera. The data are interpreted in terms of a progressive eastward advance in foldand-thrust deformation, with late Eocene Oligocene deformation in the axial zone of the Eastern Cordillera along the western edge of Floresta basin (Soapaga thrust), early Miocene reactivation (inversion) of the eastern margin of the Mesozoic rift system (Pajarito and Guaicaramo thrusts), and middle late Miocene propagation of a footwall shortcut fault (Vopal thrust) that created the Nunchia syncline in a wedge-top (piggyback) setting of the eastern foothills along the transition from the Eastern Cordillera to Harms foreland basin. Collectively, the data presented here for the frontal Eastern Cordillera define a general in-sequence pattern of eastwardadvancing fold-and-thrust deformation during Cenozoic east-west shortening in the Colombian Andes.