FUSULINID TAPHONOMY: ENCRUSTATION, BIOEROSION, CORROSION, COMPACTION, AND DISSOLUTION

The Hughes Creek Shale Member of the Foraker Limestone (Upper Carboniferous, Virgilian) in east-central Kansas contains well-preserved fusulinids, notably Triticites ventricosus (Meek & Hayden, 1858). Because of their excellent preservation, these specimens provide insight into taphonomic processes that affect fusulinids, which have been studied rarely due to the traditional use of fusulinids primarily for biostratigraphy. Analysis of 900 specimens indicates that both biostratinomic and diagenetic taphonomy of the assemblage can be recognized. The biostratinomy has involved both encrustation and corrosion. The foraminifer Tolypammina, the lone encrusting organism, is pervasive with 63 percent of the fusulinids having at least one encrusting foraminifer. Bioerosion and corrosion are not as common: only 23 percent of the specimens have significant evidence of either. Diagenesis of the fusulinids occurred during compaction of the shale and is evident as compression due to pressure solution and flattening of the tests. Pressure solution formed pits on 47 percent of the specimens, and another 3 percent reveal where other fusulinids or fossil fragments were embedded into fusulinids. Flattened or cracked specimens were not as abundant, with only 8 percent of the fusulinids having such features. Eperic seas of the Midcontinent have commonly led to densely packed fusulinid units in which they acted as the substrates for epibionts. The epibionts ranged from microbes, presumably resulting in bioerosion, to encrusting forams. The sedimentologic evidence also indicates gentle wave action in a shallow, marine setting that allowed accumulation and burial of abundant fossils. These overpacked units were then compacted resulting in flattening and dissolution of the fossils. Further study of fusulinid taphonomy will provide useful insight in the paleoenvironmental analysis of other units that are similarly packed with fossils.