Biostratigraphy and paleoecology of Asbian–Brigantian (Mississippian) miospores from Berwick-upon-Tweed, Northumberland, UK: Preliminary results

Abstract

Well-preserved, late Visean miospore assemblages from the coastline south of Berwick-upon-Tweed, Northumberland, UK, show a sequence of palynostratigraphic events stretching from the mid Asbian to the Brigantian. The assemblages belong to the Raistrickia nigra–Triquitrites marginatus (NM) and Tripartites vetustus–Rotaspora fracta (VF) biozones. Several taxa previously only recorded from pre-Brigantian strata (including Murospora parthenopia and Verrucosisporites eximius) are recorded from Brigantian rocks. The section is composed of “Yoredale” cycles reflecting cyclical changes in sea level. These features exerted control over the distribution of miospores in the section with notable trends in the vertical distributions of miospores indicative of forest mire and colonizer vegetation. Miospores representing forest mire vegetation dominate in coarser-grained rocks deposited in more proximal environments and have similar distribution patterns to rounded-triangular miospores. Conversely, non-forest mire vegetation is better represented in more proximal depositional settings, as are rounded-triangular miospores. Some samples contain mutated examples of the miospore Tripartites vetustus Schemel 1950. Mutagenesis is probably related to some, unspecified ecological stress.