Paleoenvironmental Implications of Selected Siderite Zones in the Upper Atoka Formation, Arkoma Basin, Oklahoma-Arkansas: A Look Back and Current Views on Siderite Genesis in a Sedimentary Environment

Abstract

According to the policy announced by the senior author (Campbell, 2017), this paper is based on data derived from the field work produced by the senior author during the mid-1970s as part of his research at Rice University. This paper covers field and follow-on sampling and evaluations developed from monitoring the literature on siderite genesis to date, including additional laboratory work on new samples obtained at the field sites, including incorporated carbonates and preliminary work on siderite remanent magnetism.Occurrences in the two study areas of so-called 'clayband' and "black-band" siderite and zones of siderite-replaced marine fossils and associated sediments are reported in selected sandstone and shale sequences of the upper Atoka Formation of Arkansas and Oklahoma. Outcrops near Pocola, Oklahoma and Hackett, Arkansas were examined to characterize the paleoenvironmental conditions of deposition that may have promoted the genesis of siderite. Eight types of bedded or redistributed siderite were defined, each showing specific responses to bioturbation, to physical erosion and transport, and to chemical replacement and redistribution.The clay minerals contained within the siderite zones and associated shale consist of kaolinite and illite in nearly equal proportions, with the former also possibly consisting of a kaolinite-type chamosite and the latter consisting of a significant 2M muscovite poly type. Interpretations based on sedimentary structures, texture and mineralogy of the sediments associated with the siderite zones indicate that specific sequences were likely deposited in a tidal flat or intra-deltaic environment in proximity to normal marine conditions. A primary or syngenetic origin is proposed for some of the bedded types of siderite occurrence. Other sequences indicate that marine conditions also prevailed. Physio-chemical requirements for siderite genesis suggest that siderite does not form syngenetically in a marine depositional environment but could syndiagenetically result under normal post-burial conditions involving organic-rich material (organic matter?) or a subsurface environment with a high Fe +2 :Ca +2 ratio and low SO 3 in solution. These conditions likely promoted characteristic siderization of calcareous material within marine sediments in proximity to or down the paleogeohydraulic gradient from areas of either syngenetically-produced siderite or iron-rich groundwater derived from coal-forming swamps.

The role of shelf morphology on storm‐bed variability and stratigraphic architecture, Lower Cretaceous, Svalbard

“…Interbedded sideritic mudstones represent deposition during fair‐weather conditions, whereas the associated sideritic mudstone rip‐up clasts indicate local erosion. Siderite does not form syn‐depositionally in normal marine environments, but is commonly linked to early diagenesis and reducing conditions involving organic‐rich material containing moderate amounts of iron (Campbell & Campbell, 2018).…”

Seminal Insights Concerning the Variety of Sidertic Structures and Variable Genesis and of Sideritic Occurrences: An Unexplored Source of Palaeontological Information (Sydney Coalfield, Middle Pennsylvanian, Canada)

“…The variable elemental composition of siderite is routinely used as a factor for palaeoenvironmental interpretation, or facies studies (Campbell & Campbell 2018, Cotroneo et al 2016, Seilacher 2001. Sengupta et al (2020), however, caution that pore-water geochemistry does not support that interpretation; hence, its use in palaeoenvironmental reconstructions ought to be approached with great circumspection.…”