期刊
MARINE AND PETROLEUM GEOLOGY
卷 126, 期 -, 页码 -出版社
ELSEVIER SCI LTD
DOI: 10.1016/j.marpetgeo.2021.104918
关键词
XRF; Geochemistry; Carbonate; Evaporite; Paleoenvironment; Michigan Basin
资金
- U.S. National Science Foundation, United States [EAR-IF-1636441]
Portable Energy-Dispersive X-Ray Fluorescence spectrometry (PXRF) is used to identify elemental variations in fine-grained siliciclastics. In this study, over 9000 PXRF analyses from nine drill cores are used to document variations in the carbonate mudstones of the Silurian A-1 Carbonate in the Michigan Basin. The data show that variations in the minor, non-carbonate sediment fraction within the A-1 Carbonate are regionally correlative, suggesting that siliciclastic and evaporite deposition responded in tandem to basin-wide controls on sedimentation.
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.
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