Palaeoecology, community relationships and micro-distribution of late Visean foraminifers from Boulonnais (Northern France)

摘要

Twenty-four thin sections have been made from a sample collected from a upper Visean (Early Carboniferous) outcrop. Eight foraminiferal families (Archaediscidae, Earlandiidae, Endothyridae, Eostaffellidae, Pseudoammodiscidae, Pseudotaxidae, Tetrataxidae, and Tuberitinidae) as well as bryozoan fragments, crinoidal remains, ostracods and incertae sedis (Salebridae) were identified and precisely localized within the thin section samples. The micro-distribution of foraminifers is characterized with standard and new geostatistics methods. The methods have never been applied to foraminiferal assemblages and explore the spatial structure of foraminiferal communities within the sample. Relationships between foraminifers and their sedimentological surroundings are documented with correlation and cluster analyses. The micro-distribution of foraminiferal tests and other bioclasts suggest an environment/ecological niche that was located below the fair-weather wave base. The Endothyridae and Tuberitinidae (the dominant families) are interpreted as opportunistic groups whereas the Earlandiidae are considered to be more specialized. Quantitative analysis did not reveal linear relationships between foraminifers and other groups of organisms. However the spatial distribution of crinoids can be considered as similar to those of Endothyridae and Tuberitinidae. The dataset obtained from the thin sections suggests that the paleoenvironmental interpretation will be more significant, if occurrence, density, diversity and spatial distribution data are taken into account.