In recent decades, the growing interest in wetlands highlights the fundamental role of these complex ecosystems. Integrated sedimentological and geochemical studies that refer to wetlands appear more frequently in the literature, since such approaches provide a window into understanding the functions they have played through geologic time. The Miocene Yecua Formation (Chaco foreland basin, Central Andes, Bolivia) presents sedimentological features that show how siliciclastic, chemical, and biological processes lead to lithofacies and compositional features that are distinctive of wetlands related to back-bulge settings. The succession is composed of shallowing-upward parasequences with various compositional characteristics controlled by tectonic and climatic factors.Data integration obtained from paleocurrents, petrography, and clay mineralogy show the influence of the Central Andes fold and thrust belt located to the west of the basin as a principal source area. The high compositional maturity of sandstones reflects the tectonic control as the main allocyclic variable associated with reworking of already mature sediment sources and transport factors in relation to the distal position of the basin (back-bulge), combined with climatic and paleoenvironmental conditions. XRD and SEM-EDS analyses show that illitic clays represent the main mineral phase of the clay assemblages, and have a detrital origin related to physical weathering processes in the source area. Al-rich smectitic minerals have an authigenic origin and were likely formed by alteration of volcanic detritus as well as from precursor minerals such as illite and feldspars. Kaolinite is determined to be detrital and likely derived from the erosion of floodplains with soil development. Throughout the parasequences, illite–smectite–kaolinite minerals are arranged in different proportions, showing a general vertical trend (from base to top) in which the illitic clays decrease at the expense of the increase in Al-rich smectite and kaolinite. The increase in smectite is accompanied by mixed siliciclastic–carbonate sedimentation, which points to a reduction in the clastic contribution linked to drier conditions. This vertical compositional arrangement reveals a paleoclimatic control, influenced by middle-term wet and dry periods. This work demonstrates that source-rock composition and transport distance (tectonic processes) are the key factors influencing quartz-rich sandstones and illite-rich clay mineral suites in distal positions of continental foreland basins. The long-term tropical to subtropical climate favored the development of inland wetlands and played a secondary role in the final composition of these depositional systems.

中文翻译：

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构造和古气候对安第斯中部查科前陆盆地内陆湿地沉积物组成的控制

近几十年来，对湿地日益增长的兴趣凸显了这些复杂生态系统的基本作用。涉及湿地的综合沉积学和地球化学研究在文献中出现的频率更高，因为这些方法为了解它们在地质时期所发挥的功能提供了一个窗口。中新世 Yecua 组（玻利维亚中部安第斯山脉的查科前陆盆地）呈现的沉积学特征显示了硅质碎屑、化学和生物过程如何导致与背隆设置相关的湿地特有的岩相和组成特征。层序由受构造和气候因素控制的具有各种成分特征的浅向上副层序组成。数据整合来自古洋流、岩石学、和粘土矿物学显示位于盆地西部的安第斯中部褶皱和冲断带作为主要源区的影响。砂岩的高成分成熟度反映了构造控制作为主要的异循环变量，与已经成熟的沉积物源的改造和与盆地远端（背隆起）相关的运移因素，以及气候和古环境条件相结合。XRD 和 SEM-EDS 分析表明，伊利石粘土是粘土组合的主要矿物相，具有与源区物理风化过程有关的碎屑成因。富铝蒙脱石矿物具有自生成因，很可能是由火山碎屑以及伊利石和长石等前体矿物的蚀变形成的。高岭石被确定为有害物质，很可能来自随着土壤发育的洪泛平原的侵蚀。在整个准层序中，伊利石-蒙脱石-高岭石矿物以不同比例排列，呈现出总体垂直趋势（从底部到顶部），其中伊利石粘土减少，而富铝蒙脱石和高岭石增加。绿土的增加伴随着混合硅质碎屑-碳酸盐沉积，这表明与干燥条件相关的碎屑贡献减少。这种垂直的成分排列揭示了受中期干湿期影响的古气候控制。本工作表明，烃源岩成分和运移距离（构造过程）是影响大陆前陆盆地远端富石英砂岩和富伊利石粘土矿物组的关键因素。长期的热带至亚热带气候有利于内陆湿地的发展，并在这些沉积系统的最终组成中起次要作用。