Podrobnosti záznamu

Název
    Graptolite biozonation of the Wenlock Series (Silurian) of the Builth Wells district, central Wales
Údaj o odpovědnosti
    Jan Zalasiewicz, Mark Williams
Autor
    Williams, Mark
    Zalasiewicz, Jan
Jazyk
    anglicky
Zdrojový dokument - seriál
    Geological magazine
Svazek/č.
    Vol. 136, no. 3
Strany
    p. 263-283
Rok
    1999
Poznámky
    12 obr., 2 tab., 2 s.bibl.
    Zkr. název ser.: Geol. Mag.
Předmětová skupina
    Barrandien
    Graptoloidea
    korelace stratigrafická
    pražská pánev
    silur
    wenlock
    zóny biostratigrafické
Geografické jméno
    ČR-Čechy
    Kanada-Northwest Territories
    Velká Británie
Klíčové slovo
    Biozonation
    Builth
    Central
    District
    Graptolite
    Series
    Silurian
    Wales
    Wells
    Wenlock
Abstrakt (anglicky)
   The graptolite biozonation of the Wenlock Series in the Builth Wells district is reassessed. The graptolite fauna is dominated by relatively few, but variable, species of Monograptus s.s., Pristiograptus and Monoclimacis. These species are mostly long-ranging and are of limited biostratigraphical use. Biozonation is based largely on the relatively rare cyrtograptids. The lower Wenlock Series of the district comprises the widely recognized centrifugus, murchisoni and riccartonensis biozones. The middle to upper Wenlock biostratigraphy differs from that previously recognized in the UK. Above the riccartonensis Biozone, dubius, rigidus and lundgreni biozones are distinguished. Separate flexilis and ellesae biozones are not recognized: Monograptus flexilis appears earlier than, then largely co-exists with, Cyrtograptus rigidus s.l.; while Cyrtograptus ellesae appears later than Cyrtograptus lundgreni.
   The uppermost Wenlock nassa-ludensis Biozone is sparsely fossiliferous; its subdivision has not proved possible. This revised biostratigraphical scheme for the Wenlock Series of the Builth Wells district suggests that the Sheinwoodian-Homerian boundary, as defined in the Welsh Borderland, might occur within, rather than at the base of, the lundgreni Biozone. However, difficulties in correlation with other Wenlock sequences, particularly overseas, suggest significant biofacies control, with the Wenlock seas of the Builth Wells sequences, particularly overseas, suggest significant biofacies control, with the Wenlock seas of the Builth Wells district appearing to have been periodically inhospitable to graptolites
Přispěvatel
    Česká geologická služba
Kód přispěvatele
    ČGS (UNM)
Zdrojový formát
    U
Datum vložení
    18. 2. 2008
Datum importu
    8. 8. 2012