Palynology of the upper Wenlock series (Silurian) of the Much Wenlock and Ludlow areas of Shropshire, England

• Main Author: Washington-Evans, Jane
• Published: University of Leicester 2000
• Subjects: 561
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.689345

Palynomorphs have been recovered from six localities from the type Wenlock and Ludlow series of the Much Wenlock and Ludlow areas in the Welsh Borderland, England. The assemblages contained an abundant and diverse palynoflora and palynofauna constituting elements from both the marine and terrestrial realms. Palynomorphs recovered included acritarchs, prasinophycean algae, chitinozoans and plant sporomorphs associated with scolecodonts and various palynodebris types. The samples were investigated qualitatively, semi-quantitatively, quantitatively and with fully statistical methodology. Acritarchs were recovered from all the samples and exhibited excellent preservation. The acritarchs, prasinophytes and spores are pale yellow to brown in colour, dependent on wall thickness. The chitinozoans and scolecodonts are black while the detrital amorphous organic matter is predominantly yellow/orange. The diversity and absolute abundance of the acritarchs was high throughout the sections from the Coalbrookdale, Much Wenlock Limestone and Lower Elton formations. The effect of lithofacies and palaeoenvironment and palaeoecologial tolerances upon palynomorph assemblages was apparent both in restricted distribution of some species and from lower abundances recorded from the coarse sparitic limestones. The biostratigraphical distribution of the acritarchs and prasinophytes showed that many of the forms recovered belonged to long ranging, cosmopolitan species such as Dictyotidium dictyotum, Duvernaysphaera aranaides, Diexallophasis simplex, Diexallophasis denticulata formgroup, Helosphaeridium pseudodictyum, Leiosphaeridia spp. Michrystridium stellatum, M. inflation, M. salopiense, Multiplicisphaeridium variabile, Salopidium granuliferum, Tasmanites spp. and Quadraditum fantasticum. A number of species with more restricted distributions were also recovered including the biozonal species Dictyotidium amydrum and Eisenackidium wenlockensis . Other species with a more restricted distribution included previously described forms such as Muraticavea wenlockia and Wrensnestia ornata along with a number of new species and genera, which are mostly retained in open nomenclature. Species of the new genus Bellidium were recorded with a distribution throughout the assemblages from the upper Wenlock Series. The distinctive forms defined as new species have potential use as biostratigraphic indicators. Forty-five new species of acritarch have been described systematically.