Serpukhovian in Britain: use of foraminiferal assemblages for dating and correlating

Analysis of foraminiferal assemblages from the Viséan-Serpukhovian boundary interval in Britain has led to the recognition that levels correlated with the first occurrence of Lochriea ziegleri at the base of the Serpukhovian Stage can be established by the foraminifer Neoarchaediscus gregorii in England and Scotland, which first occurs from the Single Post and Cockleshell limestones in northern England and laterally equivalent levels, as well as Asteroarchaediscus bashkiricus, and A. rugosus (except for South Wales). Contrary to some previous studies, the base of the Serpukhovian does not equate with the base of the Namurian (Pendleian Substage), but lies approximately at the early-late Brigantian boundary, based on the first occurrence of Neoarchaediscus postrugosus. Four foraminiferal assemblages are distinguished in the early Serpukhovian (7-10) and four assemblages in the late Serpukhovian (11-14). Despite the contrast in facies, it is now recognised for the first time that throughout the Midland Valley of Scotland, northern England and South Wales. the foraminiferal assemblages from shallow-water platform facies are completely compatible with the ammonoid subzones from deep-water basinal facies, with no apparent mismatches. There appears to be close comparability of foraminiferal assemblages and first appearance datums of marker species with most of the international foraminiferal zonal schemes in Russia.Supplementary material:https://doi.org/10.6084/m9.figshare.c.5240408

Late Serpukhovian Foraminifers Near the Mississippian-pennsylvanian Boundary At South Syncline Ridge, Southern Nevada, Usa: Implications For Correlation

A few, thin, Mississippian siliciclastic limestone beds, interbedded with ammonoid (uppermost Eumorphoceras Zone)-bearing shales within the South Syncline Ridge section on the Nuclear Test Site in southern Nevada, contain an abundant, low-diversity assemblage of late Serpukhovian/late Chesterian calcareous foraminifers dominated by the archaediscaceans Neoarchaediscus altiluminis, Brenckleina rugosa, Eosigmoilina robertsoni, and Betpakodiscus of the group B. attenuatus. These limestone beds were deposited in a shallow-water, clastic facies of the Scotty Wash Formation and, based on common conodont occurrences, correlate southeast to the Bird Spring Formation below the Mississippian-Pennsylvanian GSSP at Arrow Canyon, Nevada. The South Syncline Ridge foraminifers are comparable to those found in coeval beds at Arrow Canyon and represent the only other known foraminiferal assemblage to exist in association with uppermost Eumorphoceras Zone ammonoids in North America outside of Arkansas in the southern Midcontinent. Reconciliation of regional conodont and ammonoid zonations shows that the range of eosigmoiline foraminifers (E. robertsoni and B. rugosa), now generally considered an upper Serpukhovian index, extends from a position either just below or at the lower-upper boundary of the Serpukhovian Stage into the lower part of the Bashkirian Stage in North America; their upper range falls within the lower part of the Homoceras ammonoid zone beginning in the upper part of the Serpukhovian Stage. Discussion of the foraminiferal taxa includes support for retaining the genus Betpakodiscus rather than synonymizing it under Tubispirodiscus, as proposed by some specialists during the past few years.

Conodont biostratigraphy of the mid-Carboniferous boundary in Western Ireland

Two stratigraphic sections spanning the mid-Carboniferous boundary were examined in the Clare Shale Formation of the Shannon Basin in Western Ireland. Calcareous nodules intermittently occur within these generally non-calcareous organic-rich shales, and these have yielded Serpukhovian and Bashkirian conodont elements. The biostratigraphic range of the Irish material is illustrated here for the first time. Results show that the mid-Carboniferous and Arnsbergian–Chokierian boundaries are coincident at Ballybunion.Gnathodus girtyiis restricted to the lower part of the Serpukhovian Stage (Late Mississippian), whileG. bilineatus bollandensispersists into much younger strata, close to the first occurrence ofDeclinognathodus noduliferus s.l. One element belonging toG. postbilineatusis also present. These findings support the argument thatD. noduliferus s.l. developed fromG. b. bollandensis, rather than fromG. girtyi. The biostratigraphical tool for the identification of the mid-Carboniferous boundary globally, and the suitability of the section at Arrow Canyon, USA as a GSSP, may therefore need to be reassessed.

Multidisciplinary studies of global Carboniferous stage boundaries: towards a better definition and global correlations: an introduction

Earth was very dynamic during the Carboniferous with major components of the Pangea supercontinent being assembled from late Famennian to latest Pennsylvanian times, although maximum consolidation occurred during Late Permian – Early Triassic time. During the Carboniferous Period, our planet also underwent at least three major icehouse periods. The first two, in late Famennian – early Tournaisian and late Visean – Bashkirian times, indicate the onset of the Late Palaeozoic Ice Age (LPIA) with ice sheets being confined to the alpine regions of southern Gondwana. The third icehouse regime during Gzhelian – Early Permian time represents the main episode of the LPIA when a continental ice sheet developed on the Australian, Antarctic and southern African components of southern Gondwana. During the Tournaisian equatorial areas in Euramerica were occupied by extensive arid belts, in which massive carbonate deposits formed on vast platforms in that time. From the late Tournaisian into the Visean and Serpukhovian much of the equatorial belt developed into a humid-tropical realm and the former arid belt split and shifted to higher latitudes. Shelf-carbonate deposition continued over extensive areas of the continental shelves and western Palaeo-Tethys but coal swamps were developing in the forelands of the rising Appalachian and Variscan orogens. The late Serpukhovian – early Bashkirian interval saw the closure of the Rheic Ocean and a continent–continent collision between Euramerica (Laurussia) and Gondwana to form Pangea. As a consequence, a marked transition from Visean carbonate deposition to the development of coal swamps and deposition of siliciclastics during the Serpukhovian Stage occurred in many regions.

Correlation of the base of the Serpukhovian Stage (Mississippian) in NW Europe

The Task Group charged with proposing the GSSP for the base of the Serpukhovian Stage (Mississippian, Lower Carboniferous) is likely to use the global First Appearance Datum (FAD) of the conodontLochriea ziegleriin the lineageLochriea nodosa–L.zieglerifor the definition and correlation of the base of the stage. It is important to establish that the FAD ofL.ziegleriin different basins is penecontemporaneous. Ammonoids provide high-resolution biostratigraphy in the Late Mississippian but their use in international correlation is limited by provincialism. However, it is possible to assess the levels of diachronism of the First Occurrence Datum (FOD) ofL.ziegleriin sections in NW Europe using ammonoid zones. Published conodont distribution in the Rhenish Slate Mountains of Germany show the FOD ofL.ziegleriin theEmstites novalisBiozone (upper part of the P2czone of the UK and Ireland) butL.zieglerihas also been reported as occurring in theNeoglyphioceras spiraleBiozone (P1dzone). In the Yoredale Group of northern England, the FOD ofL.ziegleriis in either the P1cor P1dzone. In NW Ireland, the oldest records of bothL.nodosaandL.ziegleriare from theLusitanoceras granosumBiozone (P2a). Although there is some discrepancy in the recorded levels of the FOD ofL.ziegleriin NW Europe, this may be as a result of collection failure. The base of the Serpukhovian based on the FAD ofLochriea ziegleriwill be in the middle of the Brigantian regional Substage.

Carboniferous conodont biostratigraphy of the Dianzishang section, Zhenning, Guizhou, South China

A preliminary summary of the lower Visean to uppermost Moscovian (Carboniferous) conodont succession and biostratigraphy of the Dianzishang section in Zhenning, Guizhou, South China is presented. Eleven conodont zones, in ascending order, can be recognized:Gnathodus praebilineatus,Gnathodus bilineatus,Lochriea ziegleri,Declinognathodus noduliferus,Neognathodus symmetricus, ‘Streptognathodus’expansus(primitive form), ‘Streptognathodus’expansus,Mesogondolella donbassica – Mesogondolella clarki,Idiognathodus podolskensis,Swadelinafauna andIdiognathodus swadeizones. The first occurrences ofLochriea ziegleriat the base of the Serpukhovian Stage,Declinognathodus noduliferus noduliferusat the base of the Bashkirian Stage and ‘Streptognathodus’expansusat the base of the Moscovian Stage are recognized. The definitions of these stage boundaries, as well as that of the base of the Kasimovian Stage are discussed. Correlations with the Naqing section in South China, Russian and North American sections, as well as other important sections in the world, are considered.