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Toarcian and Bathonian (Jurassic) palynology of the Inner Hebrides, northwest Scotland.
| Riding, J.B., Walton, W. and Shaw, D. | |
| 1991 | |
| Palynology, v.15, p.115-179, pl.1-9. | |
| Toarcian and Bathonian (Jurassic) palynology of the Inner Hebrides, northwest Scotland. |
Riding, J.B., Walton, W. and Shaw, D., 1991: Toarcian and Bathonian (Jurassic) palynology of the Inner Hebrides, northwest Scotland; Palynology, v.15, p.115-179, pl.1-9. Abstract: A palynological investigation of the Toarcian to Bathonian Raasay Ironstone Formation, Bearreraig Sandstone Formation and Great Estuarine Group of the Inner Hebrides has provided an important Scottish reference section, with many stratigraphically useful dinoflagellate cyst and miospore datums. The Raasay Ironstone Formation and the Dun Caan Shales Member of the Bearreraig Sandstone Formation dinoflagellate cyst assemblages are dominated by Nannoceratopsis with the Parvocysta suite present in lower proportions. The latter suite appears to be consistent with a species diversity gradient, increasing from England northwards to Spitsbergen. Representatives of the earliest sexiform gonyaulacacean dinoflagellate cysts have their inceptions in the early Bajocian Bearreraig Sandstone Formation at its type section; possible Carboniferous spores were also recovered from this formation. The youngest member of the Bearreraig Sandstone Formation, the Garantiana Clay Member, yielded Acanthaulax crispa and other species indicative of the late Bajocian. These palynofloras are similar to coeval northwest European associations which support open marine connections southwards and eastwards at this time. The palynomorphs from the majority of the overlying Great Estuarine Group indicate a Bathonian age for these paralic strata. Palynofacies analyses are consistent with interpretations based on macrofaunas and sedimentology. The dinoflagellate cyst floras of the Duntulm Formation support a nearshore, marginal marine setting. Four new species, Parvocysta ampulla, P? tricornuta, P.? triquetra and Jansonia manifesta are described. The latter, from the Duntulm Formation, is a small, thick-walled form which has a clear partiform gonyaulacacean paratabulation. It appears to be an opportunistic species as it is abundant in marine beds immediately overlying a freshwater intercalation.