2. Distribution of microfossil Groups across the Wenlock Shelf of the Welsh Basin

The variations in environmental conditions across the shelf of the Welsh Basin during Wenlock times are reflected in the microfossil assemblages. The distribution patterns of acritarchs, chitinozoa, conodonts and ostracods are all affected, but the responses differ in each group. Many species are broadly distributed, but some are restricted to particular environments, with nearshore, shallow-water conditions having distinctive conodont and ostracod faunas. The deeper water shales of the middle Coalbrookdale Formation have few conodonts, relatively few ostracods, sphaeromorph-dominated acritarch assemblages and chitinozoan assemblages characterised by Linochitina. Most groups are most diverse in the Much Wenlock Limestone Formation, but conodonts are relatively restricted after the earliest Wenlock.