Portable Energy-Dispersive X-Ray Fluorescence spectrometry (PXRF) is routinely used to identify stratigraphic variations in the elemental chemistry of fine-grained siliciclastics. The application of this approach in carbonates is limited, however. In this study, over 9000 PXRF analyses from nine drill cores are used to document cm-scale variations in the carbonate mudstones of the A-1 Carbonate (Silurian) in the Michigan Basin. High-resolution elemental data are integrated with petrographic and mineralogical observations to evaluate the extent to which: (i) basin-center mudstones in the A-1 Carbonate (A-1C) have spatially correlative elemental signatures (i.e. chemofacies), and (ii) elemental variations reflect temporal changes in relative sea-level and sedimentation.

Spatially correlative variations in concentrations less than 5 wt% of Si, Al, K, and S are observed throughout the A-1C. Higher concentrations of Si, Al, and K are associated with more abundant siliciclastic minerals as determined petrographically and with x-ray diffraction, and are thus interpreted to reflect intensification of siliciclastic sedimentation caused by relative sea-level fall. Associated S increases reflect a higher abundance of anhydrite, which is interpreted as diagenetically altered gypsum deposited during periods of low relative sea-level. Chemofacies successions for siliciclastic and evaporite proxy elements indicate four transgressive-regressive cycles. Collectively, these data show that variations in the minor, non-carbonate sediment fraction within the A-1C are regionally correlative suggesting that siliciclastic and evaporite deposition responded in tandem to basin-wide controls on sedimentation. The observed relationship between siliciclastics and evaporites further exemplifies the broader utility of quantifying the elemental signatures and non-carbonate mineral compositions in carbonate-dominated strata to constrain sequence stratigraphic interpretations. These findings add to a growing body of work that demonstrates the utility of PXRF to generate reliable geochemical data sets and highlights the importance of integrating elemental and mineral data in sedimentological interpretations.

便携式能量色散X射线荧光光谱法（PXRF）通常用于识别细粒硅质碎屑岩元素化学中的地层变化。但是，这种方法在碳酸盐中的应用受到限制。在这项研究中，来自九个钻芯的9000多个PXRF分析被用于记录密歇根盆地A-1碳酸盐（Silurian）碳酸盐泥岩中厘米级的变化。高分辨率元素数据与岩石学和矿物学观测资料相结合，以评估以下程度：（i）A-1碳酸盐岩中的盆地中心泥岩（A-1C）具有与空间相关的元素特征（即化学相），和（ii ）元素变化反映了相对海平面和沉积的时间变化。

在整个A-1C中观察到浓度小于5 wt％的Si，Al，K和S的空间相关变化。Si，Al和K的较高浓度与岩相学测定的更丰富的硅质碎屑矿物有关，并与X射线衍射有关，因此被解释为反映了相对海平面下降引起的硅质碎屑沉积的加剧。伴随的硫增加反映了硬石膏的丰度较高，这被解释为在相对海平面低的时期沉积的成岩作用改变了的石膏。硅质碎屑和蒸发岩替代元素的化学相序表明有四个海侵-退回循环。这些数据共同表明，未成年人，A-1C内的非碳酸盐沉积物部分具有区域性相关性，表明硅质碎屑岩和蒸发岩沉积对整个盆地范围内的沉积控制均具有响应。观察到的硅质碎屑与蒸发物之间的关系进一步例证了量化碳酸盐为主的地层中元素特征和非碳酸盐矿物成分的广泛用途，以约束层序地层解释。这些发现增加了工作量，证明了PXRF在生成可靠的地球化学数据集方面的实用性，并突出了在沉积学解释中整合元素和矿物数据的重要性。观察到的硅质碎屑与蒸发物之间的关系进一步例证了量化碳酸盐为主的地层中元素特征和非碳酸盐矿物成分的广泛用途，以约束层序地层解释。这些发现增加了工作量，证明了PXRF在生成可靠的地球化学数据集方面的实用性，并突出了在沉积学解释中整合元素和矿物数据的重要性。观察到的硅质碎屑与蒸发物之间的关系进一步例证了量化碳酸盐为主的地层中元素特征和非碳酸盐矿物成分的广泛用途，以约束层序地层解释。这些发现增加了工作量，证明了PXRF在生成可靠的地球化学数据集方面的实用性，并突出了在沉积学解释中整合元素和矿物数据的重要性。