Aquatic plant microfossils of probable non-vascular origin from the Ballagan Formation (Lower Carboniferous), Midland Valley, Scotland

Abstract

SUMMARY Seven previously undescribed palynomorphs, Brazilea sp. B, ?Carbaneuletes sp. A, ?Reduviasporonites sp. and Algal palynomorph spp. 1 to 4, some of which are closely similar to the spores and filaments of extant fresh or brackish water algae, are described and illustrated from the Lower Carboniferous Ballagan Formation of central Scotland. The palynomorphs occur in a succession yielding δ 18 O and δ 13 C values from carbonate that indicate a brackish water depositional origin. They occur in several sections with a low diversity ostracod fauna dominated by Beyrichiopsis, Cavellina, Knoxiella, Shemonaella and Sulcella species, but lacking typical fully marine forms such as Bairdia and Amphissites. In addition, the sequences contain Botryococcus and Circulisporites, which are fresh to brackish water indicators, but lack spinose acritarchs that indicate marine conditions. The palynomorphs, which lack trilete marks or other haptotypic features, are thus likely to be of aquatic algal origin, and were probably produced to allow algae growing in ephemeral ponds to survive periods of desiccation and to colonize successive waterbodies in an arid coastal plain palaeoenvironment. The palynomorphs may be of value in further palaeoenvironmental studies as indicators of fresh to brackish conditions.