Algal palynomorphs of the Ballagan Formation and their palaeoenvironmental significance

The value of spores and pollen from higher vascular land plants is well established in biostratigraphic studies but their value as direct indicators of the immediate environment of deposition is limited because they are mainly dispersed, and hence represent the ecologies of variably distant terrestrial hinterlands. However, simpler spore-producing non-vascular plants such as filamentous algae live in bodies of water like lakes, ponds and lagoons, where deposition occurs, and hence have the potential to be direct indicators of palaeoenvironment.
The purpose of this report is to describe and illustrate some of the algal spores and spore-like propagules present in the palynological assemblages of the Ballagan Formation and to relate them to the four palaeoenvironments and biofacies associations that have been established by ostracod studies (Williams 2002a).
These biofacies associations have been plotted on palynological range and quantitative charts for the Heads of Ayr outcrop section, and the East Dron, Glenrothes, and Spilmersford boreholes (Figures 1-4). The charts bring together most of the palaeontological information gained during joint ostracod/palynology studies in the period 2000-2002. On the left of each chart are the sample positions, while the left hand panels illustrate palynomorph ranges and or quantitative palynological characteristics of each sample. To the right, where available, is ostracod range data.
Four ostracod biofacies associations were determined by Williams (2002a). However, on the whole it is not possible to discriminate four corresponding algal assemblages and hence there are no exact algal palynomorph proxies for these associations. However it is clear, overall, that Chomotriletes spp., Leiosphaeridia spp, Leiosphaeridia sp. A and Leiosphaeridia sp. B, ‘Monolete spore’ of McLean and Neves, R. chalastus and R. catenulatus are generally present (or abundant) within the stratigraphic range of ostracod biofacies associations 2 and 3, and therefore that such an algal assemblage can be taken as evidence for brackish to freshwater conditions. Information from extant algae, which produce similar spores to some of those above, supports such an inference.