Post-extinction recovery of terrestrial vegetation following the End Devonian Mass Extinction: integrated palynological and palaeobotanical evidence from the Tournaisian (Early Carboniferous) of the UK

Reeves, Emma J (2018) Post-extinction recovery of terrestrial vegetation following the End Devonian Mass Extinction: integrated palynological and palaeobotanical evidence from the Tournaisian (Early Carboniferous) of the UK. 10th European Palaeobotany and Palynology Conference, , Dublin, United Kingdom. 12 - 17 Aug 2018.

Abstract

As part of an investigation into the earliest Carboniferous tetrapod world, palynomorphs have been studied from a fully cored 500 m science borehole (West Mains Farm) in the Scottish Borders. Together with an outcrop section at Burnmouth, these encompass most of the Tournaisian Ballagan Formation. Both miospores and megaspores have been examined throughout, with quantitative abundances of key spore taxa enabling a robust correlation between Burnmouth and the borehole. In total, some eight distinct assemblages can be recognised through a CONISS analysis of the data. These assemblages map onto the palaeosol types present and reveal an inter-connection, with changes in climate ultimately driving a succession of vegetation types. The immediate post-extinction pattern of recovery was a simple flora, followed by increasing spore diversity. The vegetation then became dominated by the creeping lycopod Oxroadia conferta (Anaplanisporites baccatus), including abundant megaspores (Setispora pannosa). This was replaced by an assemblage dominated by Prolycospora claytonii, which new evidence suggests had an affinity with the seed plants. The palaeosols indicate that this may represent a wetter interval with more permanent vegetation and, hence, increased landscape stability. Further upsection, Oxroadia returned in abundance but was succeeded by larger arborescent lycopods with established Stigmaria root systems. But these were not lepidodendroid lycopods as they appeared significantly below the inception of Lycospora. A considerable increase in the abundance of Spelaeotriletes crustatus towards the top of the section, reveals a further change in the dominant vegetation to the ?progymnosperms. Significantly, the eight-fold subdivision of the Tournaisian can now be mapped onto long Milankovitch cycles identified in shallow marine sections.

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