A palynological study of the Quaternary succession at Afton Lodge, Scotland

The 21 samples from the Afton Lodge Quaternary succession yielded abundant and wellpreserved palynofloras, which largely comprise allochthonous Carboniferous spores and indigenous Quaternary sprores/pollen, dinoflagellate cysts and miscellaneous microplankton. Mesozoic/Palaeogene palynomorphs are present in extremely low proportions in eight of the samples. The reworked Carboniferous spores are extremely prominent in all samples studied and indicate that Carboniferous strata sourced much of this Quaternary clay. They are dominated by Densosporites spp. and Lycospora pusilla, but other taxa are present in smaller proportions. The Carboniferous assemblages are indicative of the Westphalian Series (Coal Measures), but rare Viséan-Namurian markers were also observed. Eight samples produced Mesozoic and Palaeogene palynomorphs in extremely small numbers. Most of these are of characteristically Jurassic pollen grains, largely Callialasporites spp. It is possible that these forms were derived from the Middle Jurassic of the Hebrides Basin. Single specimens of the Cretaceous dinoflagellate cyst Odontochitina operculata and the Palaeogene dinoflagellate cyst Glaphyrocysta sp. were also observed. These could be contaminants or they may have been sourced by reworking from the west. Moderately diverse indigenous Quaternary dinoflagellate cysts were recorded throughout, indicating that marine conditions were fully developed. Bitectatodinium tepikiense is the dominant species and represents c. 70-90% of the flora. Achomosphaera andalousiensis and Brigantedinium spp. are also common. This abundance of the low salinity index Bitectatodinium tepikiense is unusual and may represent an estuarine setting or freshwater input from melting ice. The overall dinoflagellate cyst and foraminiferal associations both indicate a cold, but not fully glacial environment. The Afton Lodge succession is therefore interpreted as having being deposited in an estuarine setting as opposed to in an ice melt regime; the climate was likely to have been relatively cold, but not glacial. Another hypothesis is that the abundance of Bitectatodinium tepikiense indicates a transitional ice melt regime, possibly the melting of Devensian ice. The miscellaneous microplankton observed are entirely consistent with an estuarine setting. Quaternary spores and pollen are also present. Pteridophyte spores are most prominent and indicate the presence of common-abundant ferns and mosses. This assemblage is indicative of damp/wet conditions. Arboreal (tree) pollen is rare and sporadic, indicating that trees were not commonly present close to the site of deposition. Herbaceous pollen is also present in low numbers, thereby indicating low levels of herbaceous plants. The occurrence of Armeria maritima suggests a coastal habitat. The palynofloras are relatively conservative and do not enable this section to be subdivided at fine stratigraphical precision. However, two informally designated zones, A and B have been designated.