A late Asbian (Mississippian) stratotype for England: Trowbarrow Quarry, Cumbria, UK

Abstract

A detailed biostratigraphy is established, using the high foraminiferal abundance and diversity at Trowbarrow Quarry, which is also proposed as a stratotype section for the late Asbian (late Visean), a substage not previously formally subdivided. The foraminiferal assemblages suggest that the early Asbian has to be revised, which has implications for the chronostratigraphy of many late Visean outcrops in Britain, which are probably erroneously interpreted. From the upper part of the Park Limestone Formation at Trowbarrow Quarry, near the base of the section, the transition between foraminifers assigned to the early and late Asbian (Cf6α–β to Cf6γ subzones) is identified. The Urswick Limestone Formation contains excellent biostratigraphic records of many important taxa, enabling the subdivision of the formation into five foraminiferal assemblage zones for the late Asbian, namely Cf6γ1a, Cf6γ1b, Cf6γ2a, Cf6γ2b and Cf6γ2c. The last assemblage is currently recognized only in the North Pennines and at Trowbarrow. These assemblages enable revision of the stratigraphic range of many taxa used as biostratigraphic markers in Britain and Ireland. Owing to its excellent foraminiferal record, the late Asbian subdivisions will significantly facilitate the reinterpretation of other well‐known Asbian platform carbonate successions in Britain. Although there are some faunal differences, the base of the late Asbian can be confidently correlated to other European zonal schemes, with its base being equivalent to the base of the former V3bγ or more recent MFZ14 foraminiferal zones of Belgium, and the base of the Mikhailovian Substage in Russia.

Middle to Late Mississippian and Early Pennsylvanian foraminiferal zonal scheme of South China—a case study from the Youjiang Basin: biostratigraphical and palaeobiogeographical implications

“…Makhlina et al 1993), and from the early Asbian in England (e.g. Cózar et al 2022bCózar et al , 2022c. No palaeokarst has been detected in this lower part of the section, and a continuous succession is inferred.…”

“…A recent revision of the Asbian in the type region, however, suggests that the Asbian boundary Stratotype is not represented by any micro-and macrofaunal zone. The supposed foraminiferal Cf6 Zone that should characterize the base of this substage is actually located at a few tens of metres below the current position of the Asbian (Cózar et al 2022b), including those records of Palaeotextularia, and thus, its occurrence is not confirmed to occur in the Cf5 Zone in Britain. The occurrence of Pseudoendothyra might also suggest that the assemblage is more similar to those from the Russian Platform, because in the classical zonation of Western Europe, this genus is used as a marker for the lower Asbian Cf6β Subzone or the upper part of the lower Warnantian MFZ13 Zone (e.g.…”

New species and evolution of the foraminiferal family Janischewskinidae in the middle–upper Mississippian of South China

“…Remarks. The composition of this genus has been usually restricted to the original species described by Strank (1984), although Cózar et al (2022) also included B. moldensis, the type species of the monospecific genus Groessensella, and some ancestral forms (Bibradya? sp.…”

“…However, the biostratigraphy of these genera in other basins does not support the phylogenetic lineage. Parajanischewskina is restricted in Britain to the uppermost Asbian to the lowermost Brigantian (Cózar and Somerville, 2004;Waters et al, 2017;Cózar et al, 2022), whereas the first Janischewskina (J. typica) occurred in the late Brigantian (= early Serpukhovian) (Cózar and Somerville, 2021), as a result, there is a significant gap without any representatives of both genera. Richer Janischewskinidae assemblages from the Russian Platform show small species of Janischewskina from the Aleksinian (FAD), at coeval levels with Bradyina, whereas the large species of Janischewskina occur from the Mikhailovian (Kabanov et al, 2016;Gibshman et al, 2020).…”

“…The family Janischewskinidae is rather diversified in the Moscow Basin, where in the southern part, there are better biostratigraphic and lithostratigraphic controls, but it is possibly more abundant in the western part, and there, some species exhibit longer stratigraphic ranges, such as the large Janischewskina (compare Makhlina et al, 1993and Kabanov et al, 2016with Savitsky et al, 2015and Gibshman et al, 2020. In Western Europe, although species diversity is lower than that in the Russian Platform (e.g., Somerville, 2006, 2021;Vachard et al, 2016;Cózar et al, 2022), the family is common (e.g., Conil et al, 1980), with some well-known species being absent and/or their first occurrences being much later than those in the Moscow Basin in some cases (e.g., Cózar et al, 2019;Cózar and Somerville, 2021). Species diversity in the Urals and Ukraine seems to be also lower than that in the Moscow Basin (see Aizenverg et al, 1968;Vdovenko, 2001;Stepanova and Kucheva, 2009;Kulagina et al, 2019;Kulagina, 2022).…”