Silurian Palynomorphs

Abstract. The data obtained from an independent study of acritarchs, chitinozoans and miospores enables the determination of maximum age ranges of samples taken from three wells. These are shown in Fig. 8.

ACRITARCHS

At present, samples have been examined from six wells – A1-46, Core 2; E1-81, Cores 3, 4; F1-46, Core 3; D-31, Core 1; A1-81, Core 3 and C1-31, Core 8. The last mentioned is considered no further here as all samples have to date proved barren. The oldest of the acritarch assemblages are recorded from E1-81, Cores 3, 4 between 1850ft. and 2340ft. (Fig. 8) and from A1-81, Core 3 between 3750ft. and 3773 ft. These are dominated by the polygonomorph acritarchs, Veryhachium trispinosum and V. valiente but also include acanthomorphs such as Diexallophasis and Multiplicisphaeridium. The lack of diagnostic acritarchs of post convolutus zone would indicate the age of the samples as Rhuddanian to Early Aeronian but no higher than convolutus zone. Wells A1-46, Core 2 between 9710 to 9721 ft. (Fig. 8); D1-31, Core 1, 6105 to 6160ft. (Fig. 8) and F1-46, Core 3, 8852 to 8858 ft. all yield rich assemblages dominated by Multiplicisphaeridium, Diexallophasis and Veryhachium and characteristic species of Visbysphaera, Cymbosphaeridium, Oppilatala and ?Dateriocradus. The presence of forms such as Oppilatala eoplanktonica, ?Dateriocradus monterrosae, Multiplicisphaeridium arbusculiferum, Diexallophasis caperoradiola and Visbysphaera gotlandicum indicate the assemblages are of post-convolutus zone age, thus late Aeronian, as an oldest date.

Regional palynological differences in the acritarch assemblages are observed between North Africa and Great Britain, which are consistent . . .