57-5 Integrating Benthic Foraminiferal Biostratigraphy and Geochemistry to Investigate Siderite Formation in Late Pennsylvanian Cyclothems of Northeastern Kansas

Abstract:

The origin and depositional significance of siderite within Late Pennsylvanian strata of the Midcontinent region remains incompletely understood due to limited biostratigraphic and paleoenvironmental constraints. This study integrates benthic foraminiferal analysis with petrographic and geochemical investigations to evaluate the formation of siderite-bearing intervals recovered from the PNR#1 and Edmonds A1 cores in northeastern Kansas. The studied succession consists of cyclic coal beds interbedded with shale, limestone, and sandstone, containing siderite-rich horizons that record episodes of enhanced chemical weathering and iron accumulation within the depositional system.

Benthic foraminifera were examined to establish age control and reconstruct depositional conditions, providing critical stratigraphic information in a region where detailed micropaleontological studies are scarce. The recovered assemblages offer valuable insights into environmental fluctuations associated with Pennsylvanian cyclothems and help refine the biostratigraphic framework of Midcontinent strata. Mineralogical and geochemical characterization was conducted using petrographic observations and Energy Dispersive Spectroscopy (EDS) to determine the elemental composition and distribution of siderite within the cores.

The combined micropaleontological and geochemical data indicate that siderite formed under low-oxygen, iron-rich conditions in brackish- to freshwater wetland settings associated with coal-forming environments. The presence and distribution of benthic foraminifera further suggest periodic marine influence during sediment deposition. These findings demonstrate the importance of benthic foraminifera not only for establishing the age of Pennsylvanian successions but also for reconstructing paleoenvironmental conditions in the Midcontinent region. The study provides new insights into the controls on siderite precipitation and enhances our understanding of the complex interactions among climate, sedimentation, and ecosystem dynamics during the Late Pennsylvanian .

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