X-ray fluorescence chemostratigraphy of the Cenomanian–Turonian Woodbine and Eagle Ford Groups in the southern parts of the East Texas Basin highlights significant mudstone chemical heterogeneities that commonly are difficult to observe or quantify at the macroscale. Several key elements, namely, Ca, Si, Mo, Mn, and Ni, were correlated to depositional conditions and used in a hierarchical cluster analysis to characterize five chemical facies (i.e., “chemofacies”) across 10 cored intervals of the Woodbine and Eagle Ford Groups: (1) argillaceous, organic-matter poor; (2) transitional, organic-matter poor; (3) transitional, organic-matter moderate; (4) calcareous, organic-matter rich; and (5) calcareous, organic-matter moderate. Characterizations of organic matter richness, mineralogy, and environmental conditions of deposition were established by correlating between key element abundances, total organic carbon measurements, x-ray diffraction measurements, and petrographic observations of lithologic composition, bioturbation, and sedimentary textures. Combined analysis of elemental geochemistry, stratigraphy, and petrographically observed sedimentary textures indicates that all chemofacies were deposited in an intrashelf basin above storm wave base. The most organic-rich chemofacies was deposited on a dominantly dysoxic distal shelf. Mudstone organic matter enrichment is driven dominantly by the minimization of siliciclastic dilution and secondarily enhanced by oxygen restriction.Regional correlations of chemofacies within a sequence stratigraphic framework developed from previous outcrop and subsurface work indicate a clear relationship between interpreted stratigraphy and chemofacies deposition. Generally, the highstand sequence sets of the Woodbine Group and upper Eagle Ford formation are dominated by mineralogically clay-rich, organic matter–lean, siliciclastic sedimentation and contain poor-quality source rock. Conversely, the transgressive sequence set of the lower Eagle Ford formation is dominated by organic matter–rich pelagic carbonate accumulation and contains excellent-quality source rock.

中文翻译：

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东德克萨斯州南部（布拉索斯）盆地伍德宾和伊格福特组的沉积环境和烃源岩质量：综合地球化学，层序地层学和岩石学方法

东得克萨斯盆地南部地区的西诺曼尼亚–突尼斯Woodbine和Eagle Ford组的X射线荧光化学地热图强调了重要的泥岩化学异质性，这些异质性通常很难在宏观尺度上观察或量化。Ca，Si，Mo，Mn和Ni的几个关键元素与沉积条件相关联，并用于层次聚类分析中，以表征Woodbine和Eagle的10个去核间隔中的五个化学相（即“化学相”）。福特集团：（1）泥质，有机质较差；（2）过渡性，有机性差；（3）过渡性，有机物适度；（4）钙质，有机质丰富；（5）钙质，有机质中等。有机质丰富度，矿物学，通过确定关键元素的丰度，总有机碳测量值，X射线衍射测量值以及岩性，岩性扰动和沉积质地的岩石学观测结果之间的相关性，确定了沉积物的沉积条件和环境条件。对元素地球化学，地层学和岩石学观察到的沉积质地的综合分析表明，所有化学沉积物都沉积在风暴波基上方的陆架内盆地中。最富含有机物的化学沉积物沉积在主要为低氧的远端支架上。泥质有机质的富集主要是由硅质碎屑的最小化驱动，其次是氧气限制。从先前的露头和地下工作发展而来的层序地层学框架内，化学岩相的区域相关性表明，解释的地层与化学岩相沉积之间存在明确的关系。通常，Woodbine组和上层Eagle Ford地层的高位层序集主要由矿物学上富含粘土，有机质稀薄，硅质碎屑沉积而成，并且包含劣质的烃源岩。相反，较低的Eagle Ford地层的海侵层序集则以富含有机质的上层碳酸盐岩的堆积为主导，并包含优质的烃源岩。硅质碎屑沉积和含有劣质烃源岩。相反，较低的Eagle Ford地层的海侵层序集则以富含有机质的上层碳酸盐岩的堆积为主导，并包含优质的烃源岩。硅质碎屑沉积和含有劣质烃源岩。相反，较低的Eagle Ford地层的海侵层序集则以富含有机质的上层碳酸盐岩的堆积为主导，并包含优质的烃源岩。