Graptolites in British stratigraphy

Abstract

697 taxa of planktonic graptolites are recorded, and their stratigraphical ranges are given, through 60 biozones and subzones in the Ordovician and Silurian strata of England, Wales and Scotland, in the first such stratigraphical compilation for Great Britain since the synthesis of Elles & Wood (1901-1918.

Gauging the impact of glacioeustasy on a mid-latitude early Silurian basin margin, mid Wales, UK

“…12, curve 22), where Loydell et al (2009; 559 view it as evidence for a glacioeustatic sea-level fall. However, the likely impact of 560 glacioisostasy in this region persuaded Johnson (2010) that the local record of base level movements may not accurately reflect global events (see also Berry and Boucot, 1973).…”

Graptolites from the Rhuddanian-Aeronian boundary interval (Silurian), Prague Synform, Czech Republic

“…The long-ranging species Rhaphidograptus toernquisti (Elles & Wood) and Korenograptus nikolayevi (Obut) have their lowest occurrences in the upper vesiculosus Biozone. The graptolite assemblage of the upper vesiculosus Biozone in the Prague Synform is correlatable with the lower part of the Huttagraptus acinaces Biozone of the British Isles in the sense of Zalasiewicz et al (2009).…”

“…Whilst Nd. magnus gives its name to a biozone above the triangulatus Biozone in the British scheme (Rickards 1976b, Zalasiewicz et al 2009, Nd. fezzanensis is a prominent constituent of the cyphus Biozone assemblages at all relevant sections of the Prague Synform.…”

“…The strongly curved rhabdosome and slight thecal overlap on the other hand differentate this specimen from the otherwise closely similar Huttagraptus acinaces (Törnquist). Both species are known from about the same stratigraphical level -acinaces (upper vesiculosus -lower cyphus) Biozone of the British biozonal scale (Hutt 1974, Zalasiewicz et al 2009). …”

A Kralodvorian (upper Katian, Upper Ordovician) benthic association from the Ferradosa Formation (central Portugal) and its significance for the redefinition and subdivision of the Kralodvorian Stage

“…This taxon occurs in Pleurograptus linearis Zone strata in Baltica (Bornholm and Sweden) (Kraft et al 2015). However, since the range of the P. linearis Biozone in England and Wales (Ka2-Ka3) extends from the regional uppermost Caradoc until (at least) the middle part of the Rawtheyan Substage of the type Ashgillian (Rickards 2002(Rickards , 2004Zalasiewicz et al 2009), the correlation proposed by these authors with the Caradoc-Ashgill boundary of the regional British scheme has been considered imprecise (Gutiérrez-Marco et al 2017). Štorch & Mergl (1989) placed the Kralodvorian-Kosovian boundary in the Prague Basin by the sudden extinction of the high diversity Proboscisambon Community ("Perník Bed") and (Hammann, 1992), internal mould of a librigena, MG15711.…”