Taphonomical analysis of the infilling and early mineralization in endothyroids (Foraminiferida, Mississippian)

In the last few years, many studies have focused on the recognition of the allochthonous or reworked foraminiferal tests. Several features are usually analyzed, such as sorting and orientation. However, the first step to understand the processes related to the taphonomic alterations is to analyze and understand the mechanisms of infilling, and the early mineralization that foraminiferal tests suffered during the biostratinomic stage and early diagenesis. The main challenge of this contribution is to recognize and compare the processes occurring in the endothyroids that have also been described in macrofossils and some other features that are only recognized in these small foraminifera. Three mechanisms of infilling are recognized in Mississippian (Early Carboniferous) foraminiferal tests: currents, aspired currents and gravity. Infilling due to bioturbation is not recognized. The quantity of micrite sediment, extension, and shape are different and distinctive of the infilling mechanism. Moreover, the infilling is interpreted in some instance to have been modified in later stages due to mechanical breakage of the test, gravity or superficial tension among particles. Later or simultaneous with the infilling, mineralization began, which was continuous during early diagenesis. This early mineralization is related to either environmental conditions, diagenetic as well as sedimentary, or biologic features. Several processes have influenced mineralization including the type of cements, formation of molds, neomorphism and silicification.