The sedimentology, palaeoecology and preservation of the Lower Carboniferous plant deposits at Pettycur, Fife, Scotland

Abstract

AbstractThe Lower Carboniferous (Asbian) sediments and volcanics of the Pettycur region in Fife, Scotland, yield several important anatomically preserved floras including that from the famous ‘Pettycur Limestone’. The plant fossils are preserved as calcareous permineralizations and fusain within limestone blocks which occur at the base of basaltic lava flows or within pyroclastic sequences. The geology and sedimentology of these plant deposits have been investigated, and it is demonstrated that a number of plant-bearing facies can be recognized which reflect different modes of transport, deposition and fossilization. Of these facies the ‘Pettycur Limestone’ is the most well known. The lithology is composed of a distinct assemblage dominated by lycopods and the pteridosperm, Heterangium. Other assemblages include a limestone dominated by zygopterid ferns which are frequently fusainized and the Kingswood Limestone which contains a completely different flora to that at Pettycur, being dominated by pteridosperms, other gymnosperms and the lycopod Oxroadia. Each sediment type is characterized by a distinct mineralization history of the plants reflecting different sites of fossilization.A hypothesis concerning the original ecology of the plant assemblages within the basaltic volcanic terrain is proposed. It is suggested that the Pettycur Limestone represents an established original peat within which the plants were permineralized. The zygopterid ferns occupied sites which were susceptible to wildfire and did not establish long-lived peat-forming communities. The Kingswood flora was established in a region where plants were prone to fire and then subsequently transported into an area of limestone deposition along with unburnt plant fragments. This flora was separated by space and/or time from the Pettycur floras. Lakes developed on lava surfaces and provided sites of fossilization for plant fragments as compressions.