Podrobnosti záznamu

    High-resolution magnetostratigraphy and micropaleontology across the J/K boundary strata at Brodno near Žilina, western Slovakia: summary of results
Údaj o odpovědnosti
    Václav Houša, Miroslav Krs, Marta Krsová, Otakar Man, Petr Pruner, Daniela Venhodová
    Houša, Václav
    Krs, Miroslav, 1928-
    Krsová, Marta
    Man, Otakar
    Pruner, Petr
    Venhodová, Daniela
Zdrojový dokument - seriál
    Cretaceous research
    Vol. 20, no. 6
    p. 699-717
    14 obr., 4 tab., 23 bibl.
    Zkr. název ser.: Cretaceous Res.
Předmětová skupina
    demagnetizace tepelná
    stratigrafická hranice
    Západní Karpaty
    zóny biostratigrafické
Geografické jméno
Klíčové slovo
Abstrakt (anglicky)
   This study summarized the final results of magnetostratigraphic and micropalaeontological investigations of the Tithonian/Berriasian boundary (J/K) limestones at the locality of Brodno near Žilina, Western Carpathians, West Slovakia. The aim is to prepare the backgroundfor correlation of a Late Tithonian and Early Berriasian biostratigraphic zonation with global particularly the Boreal and Pacific realms. Suiable physical properties of the limestones studied, a favourable geological setting and rich microfossil assemblages (calpionellids) at Brodno (magnetozones M21r to M18r) allowed a systematic collection of new data on the original synoptic section, which now has the character of a high-resolution profile across the J/K Subzone , respectively. Both can be correlated with analogous subzones in the M-sequence of marine anomalies. Their existence can also be confirmed in the Bosso Valley section in Umbria, central Italy.
   A detailed study of the interval between magnetozones M20n and M17r in the Bosso Valley profile is presently in its final stage. Both magnetostratigraphic profiles, from the Brodno and Bosso Valley localities, werethoroughly investigated in the intervals close to the J/K boundary and are still unique among continent-based profiles in the detection and precise definition of both reverse subzones within M20n and M19n. Samples collected from the boundary strata of the reverse Kysuca Subzone at Brodno indicated a transition from N (R) to R (N) polarity of the Earth s palaeomagnetic field within a time intervalof c.+-5 ka. Limestone samples (total number n=368) were subjected to progressive thermal demagnetization in 10-12 thermal fields and to subsequent multi-component analysis of remanence. The C-component as the carrier of palaeomagnetic directions, was determined in the temperature interval of 300° to 540°, or possibly 580°C.
   Magnetomineralogical analyses of pilot samples and unblocking temperatures determined for all samples showed that magnetite is the carrier of remanent magnetization. The position of the individual events of calpionellid stratigraphyrelative to the global magnetic polarity timescale are precisely defined. The base of the Calpionella Standard Zone, which is considered a provisional J/K boundary indicator in ammonite-free sections in the Tethyan realm, lies within magnetozone M19n at the level of 35 of percents local thickness. None of the boundaries in the calpionellid zonation coincides precisely with any of those in the palaeomagnetic zonation, but the first appearance of Calpionella grandalpina, indicating the base of the Intermedia Subzone, lies in close proximity to the base of magnetozone M19r
    Česká geologická služba
Kód přispěvatele
    ČGS (UNM)
Zdrojový formát
Datum vložení
    25. 3. 2008
Datum importu
    8. 8. 2012