Lycopod succession in coals: an example from the Low Barnsley Seam (Westphalian B), Yorkshire, England

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Abstract
Lycopsid megaspores processed from petrologically defined samples of the Low Barnsley Seam, Westphalian B, Upper Carboniferous have vertical distributions arranged in repeated successions of phases. A total of six phases was distinguished producing a more detailed pattern of succession than has previously been identified using miospores. Two important phases were recognized for the first time, designated: Phase 0, characterized by the species Cystosporites verrucosus Dijkstra, Lagenicula horrida Zerndt, Pseudovalvisisporites nigrozonalis (Stach & Zerndt) Lachkar and Cystosporites giganteus (Zerndt) Schopf, interpreted as a colonizing assemblage, and Phase 2, characterized by the species Triangulatisporites tertius Potonié & Kremp and Valvisisporites auritus (Zerndt) Potonié & Kremp which is considered to represent an association of non-arborescent lycopods. Phases are broadly related to petrographic type(s) but changes in phases and petrography are not necessarily coincident. Phasal changes of the kind described are believed to result from the formation of a raised bog.