Basement influences on dolomite-hosted vertical sedimentary intrusions in marine erg-margin deposits from the Pennsylvanian of Northern Wyoming (USA)

Blanchard, Sébastien; Frank, Tracy D.; Fielding, Christopher R.

doi:10.1016/j.sedgeo.2016.03.023

Cited by 2 publications

(1 citation statement)

References 66 publications

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“…). The ptygmatically folded character of thin (<5 cm) vertical, sandstone intrusions found in marine dolomite, as well as the folding of layers above and below thicker (>10 cm) intrusions that acted as pillar‐like bodies during burial (Blanchard et al, in press), indicate that marine intervals were noticeably compacted. The compaction rate for such deposits can also be estimated using the lateral difference in thickness between layers folded around intrusive bodies.…”

Section: Magnitude Of Glacio‐eustatic Fluctuationssupporting

confidence: 66%

Sequence stratigraphic framework for mixed aeolian, peritidal and marine environments: Insights from the Pennsylvanian subtropical record of Western Pangaea

et al. 2016

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Due to difficulties in correlating aeolian deposits with coeval marine facies, sequence stratigraphic interpretations for arid coastal successions are debated and lack a unifying model. The Pennsylvanian record of northern Wyoming, USA, consisting of mixed siliciclastic–carbonate sequences deposited in arid, subtropical conditions, provides an ideal opportunity to study linkages between such environments. Detailed facies models and sequence stratigraphic frameworks were developed for the Ranchester Limestone Member (Amsden Formation) and Tensleep Formation by integrating data from 16 measured sections across the eastern side of the Bighorn Basin with new conodont biostratigraphic data. The basal Ranchester Limestone Member consists of dolomite interbedded with thin shale layers, interpreted to represent alternating deposition in shallow marine (fossiliferous dolomite) and supratidal (cherty dolomite) settings, interspersed with periods of exposure (pedogenically modified dolomites and shales). The upper Ranchester Limestone Member consists of purple shales, siltstones, dolomicrites and bimodally cross‐bedded sandstones in the northern part of the basin, interpreted as deposits of mixed siliciclastic–carbonate tidal flats. The Tensleep Formation is characterized by thick (3 to 15 m) aeolian sandstones interbedded with peritidal heteroliths and marine dolomites, indicating cycles of erg accumulation, preservation and flooding. Marine carbonates are unconformably overlain by peritidal deposits and/or aeolian sandstones interpreted as lowstand systems tract deposits. Marine transgression was often accompanied by the generation of sharp supersurfaces. Lags and peritidal heteroliths were deposited during early stages of transgression. Late transgressive systems tract fossiliferous carbonates overlie supersurfaces. Highstand systems tract deposits are lacking, either due to non‐deposition or post‐depositional erosion. The magnitude of inferred relative sea‐level fluctuations (>19 m), estimated by comparison with analogous modern settings, is similar to estimates from coeval palaeotropical records. This study demonstrates that sequence stratigraphic terminology can be extended to coastal ergs interacting with marine environments, and offers insights into the dynamics of subtropical environments.

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Section: Magnitude Of Glacio‐eustatic Fluctuationssupporting

confidence: 66%

Sequence stratigraphic framework for mixed aeolian, peritidal and marine environments: Insights from the Pennsylvanian subtropical record of Western Pangaea

et al. 2016

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Dolomitization of supratidal to shallow-marine carbonates in the Pennsylvanian successions of the Wyoming Shelf

Blanchard

Frank

Fielding

2016

MT GEOL

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Laterally extensive beds of dolomitized carbonate are found interbedded with eolian to peritidal sandstones in the hydrocarbon-producing Pennsylvanian to earliest Permian successions of the Wyoming Shelf, USA. Subsurface and surface correlations often rely on these dolomite intervals yet their origin is poorly constrained. To characterize the nature of dolomitization, we integrate petrography, carbon and oxygen isotope data, and sedimentological characteristics of pervasively dolomitized shallow-marine, supratidal, and pedogenic facies in the Amsden and Tensleep Formations of the Bighorn Basin (early to middle Pennsylvanian, northern Wyoming). Stable isotopic compositions are compared with the documented isotopic signature of protodolomite forming on present-day arid coastlines. The composition of fine- to medium-grained dolomitized matrix differs from that of late-stage calcite spars, suggesting that dolomites preserve a primary or early diagenetic signal. The δ18O values of dolomites (-1.2 to 7.6‰ VPDB) display a similar range to that of modern protodolomite forming in the tidal flats of the coast of Abu Dhabi. The δ13C values, however, are consistently lower than expected if dolomite had precipitated from sea-water. These relationships suggest that dolomite incorporated a considerable amount of isotopically light carbon during primary formation or later during overgrowth and/or recrystallization of the initial protodolomite. Pennsylvanian and earliest Permian successions in Wyoming, Montana, and northeastern Utah display very similar diagenetic modifications (i.e., pervasive dolomitization, evaporite replacement, silicification), suggesting that the models discussed here may be applicable to these contemporaneous formations.

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Basement influences on dolomite-hosted vertical sedimentary intrusions in marine erg-margin deposits from the Pennsylvanian of Northern Wyoming (USA)

Cited by 2 publications

References 66 publications

Sequence stratigraphic framework for mixed aeolian, peritidal and marine environments: Insights from the Pennsylvanian subtropical record of Western Pangaea

Sequence stratigraphic framework for mixed aeolian, peritidal and marine environments: Insights from the Pennsylvanian subtropical record of Western Pangaea

Dolomitization of supratidal to shallow-marine carbonates in the Pennsylvanian successions of the Wyoming Shelf

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