Pennsylvanian (mid-Bolsovian to Asturian) megaspores and large pollen of the Bristol Coalfield, UK

Janine L Pendleton,Charles H Wellman

doi:10.1144/jmpaleo2012-001

Abstract

Abstract. A detailed account of assemblages of megaspores and large pollen grains from the mid-Bolsovian to late Asturian Warwickshire Group (Winterbourne, Pennant Sandstone and Grovesend formations) of the Bristol Coalfield is presented. The megaspore assemblages show certain similarities to those from the well-documented, and partly coeval, sequence in the nearby Forest of Dean Coalfield. However, the Bristol Coalfield megaspore assemblages are generally less diverse. We consider the palaeoecological implications of the megaspore assemblages and conclude that differing depositional settings had different vegetational successions (including differences in the composition and diversity of megaspore-producing plants). A consideration of megaspore biostratigraphy suggests that the uppermost Pennant Sandstone Formation may be of early Asturian age, suggesting that the postulated gap between the Pennant Sandstone Formation and overlying Grovesend Formation is smaller than previously suggested. We also report the first European occurrence of the large enigmatic pteridosperm pollen grain Parasporites maccabei Schopf, 1938.

Highlights

This paper focuses on a series of assemblages of megaspores and large pollen grains recovered from numerous horizons spread throughout the Warwickshire Group that range from midBolsovian to late Asturian (Moscovian) in age
Megaspores and Large poLLen graIns: a paLaeobotanIcaL perspectIve Megaspores are common in the Carboniferous Coal Measures where they are found in situ (e.g. Chaloner, 1953a, b, c; 1956) and dispersed (e.g. Spinner, 1965)
The vast majority of megaspores from the Carboniferous Coal Measures derive from lycopsids

Summary

Introduction

IntroductIon The Coal Measures Supergroup of the Bristol Coalfield has been little studied in comparison to other British Coalfields, such as the nearby Forest of Dean Coalfield (e.g. Arber, 1912; Spinner, 1965; Cleal, 1991) and South Wales Coalfield (e.g. Dix, 1934; Dimitrova et al, 2005; Cleal, 2007). The Warwickshire Group of the Bristol Coalfield comprises from base to top: the Winterbourne, Pennant Sandstone and Grovesend formations. In the Forest of Dean, roof shale megafloras from the Coleford High Delf Coal, which roughly equates to the base of the Pennant Sandstone Formation, suggests a late Asturian age in this northernmost area (Wagner & Spinner, 1972; Cleal, 1991; 1997).

Results

Conclusion