High-resolution chemostratigraphy in carbonate mudstones: Salina A-1 carbonate (Silurian), Michigan Basin, U.S.A. (April 2021)

• Record Type: Journal Article
• Authors: Hemenway, Matthew A.; Kaczmarek, Stephen E.
• Is Part Of: Marine and petroleum geology. Volume 126(2021)
• Publication Date: 2021-04
• Subjects: XRF -- Geochemistry -- Carbonate -- Evaporite -- Paleoenvironment -- Michigan Basin; Submarine geology -- Periodicals; Petroleum -- Geology -- Periodicals; Géologie sous-marine -- Périodiques; Pétrole -- Géologie -- Périodiques; Petroleum -- Geology; Submarine geology; Periodicals; Electronic journals; 551.468
• DOI: 10.1016/j.marpetgeo.2021.104918
• Languages: English
• ISSNs: 0264-8172

Abstract

Abstract: 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. Highlights: PXRF for chemostratigraphic analysis is less established in carbonate rocks. Integrated XRD and PXRF data is necessary to inform geologic interpretations. Non-carbonate sediments are the key to interpreting sequence stratigraphy in the A-1C.