Dubki (Saratov region, Russia), the reference section for the Callovian/Oxfordian boundary

• Autorzy: Kiselev D. , Rogov M. , Guzhikov A. , Pimenov M. , Tesakova E. , Dzyuba O.
• Konferencja: International Congress on the Jurassic System (7 ; 06-18.09.2006 ; Kraków, Poland)
• Języki publikacji: EN

Abstrakty

EN

Efforts in the choosing of GSSP for the Cl/Ox boundary have led to distinction of some available sections with good succession of the ammonite faunal horizons in the vicinities of Saratov. One of the primary criteria for GSSP proposal is the good traceability across the world, and hence, the study of reference section (especially in the region with mixed faunas) in the terms of integral stratigraphy. Additional importance of the investigation of the reference sections for the Cl/Ox boundary is connected with wide distribution of the condensed facies and gaps perhaps due to the suggested sharp changes in climate of the Northern Hemisphere. Few variants of the infrasubzonal units for the Cl/Ox transitional beds of the Russian Platform were suggested recently. Here we are using the scheme of Kiselev and Rogov (2005). The Dubki section is located few kilometers north from Saratov and originally was a temporary quarry for the nearby road-building. Recently this section and/or ammonites from this section were briefly described by Mitta (Keupp & Mitta 2004) and by the present authors (Rogov & Egorov 2003). In addition, this section has recently been proposed as possible candidate for the Cl/Ox GSSP (Kiselev & Rogov 2004). Precise ammonite sampling permits establishing a succession of faunal horizons close to that of Northwest Europe (Fig. 1). Inclined boundaries between some horizons in the figure mean short transitional span, where index species (or both morphologies in lineage) co-occur. Only ranges of the few, most important taxa are shown. Strong Tethyan influence is fixed in the mojarowskii and baccatum horizons, while Boreal cardioceratids dominate in the other intervals. Among the Belemnitida two main groups are recorded. Belemnotheutids are generally scarce; they range from Henrici to Praecordatum subzones. Belemnitids are typically of Tethyan origin (Hibolithes). Boreal forms are common only in two restricted levels. Ostracods are numerous and diverse. However, they show wide oscillations in these two characters through the section, possibly reflecting sea-level changes. Remarkably, Infacythere dulcis is replaced by Nophrecythere oxfordiana at the Cl/Ox boundary as determined by ammonite biostratigraphy. Quite exceptionally, some levels in the studied section provided good samples for magnetostratigraphic studies across the Cl/Ox boundary. Lamberti Zone is chiefly characterized by normal polarity, whereas Mariae and Cordatum zones show dominant reverse polarity, corresponding to polarity structure of the M-35-M37 Chrons (Ogg 2004).

Słowa kluczowe

EN

Callovian-Oxfordian boundary; reference section; integrated stratigraphy

• Wydawca: Państwowy Instytut Geologiczny - Państwowy Instytut Badawczy
• Czasopismo: Volumina Jurassica
• Rocznik: 2006
• Tom: Vol. 4, no. 1
• Strony: 177--179
• Opis fizyczny: Bibliogr. 5 poz.

Twórcy

autor

Kiselev D.

autor

Rogov M.

autor

Guzhikov A.

autor

Pimenov M.

autor

Tesakova E.

autor

Dzyuba O.

• 1Yaroslavl State Pedagogical University, Kotoroslnaya nab. 46, Yaroslavl 150000, Russia; e-mail: [e-mail] 2Geological Institute of RAS, Pyzhevskii Lane 7, Moscow 109017, Russia,

Bibliografia

• Keupp H. and Mitta V. V. 2004. Septenbildung bei Quenstedtoceras (Ammonoidea) von Saratov (Russland) unter anomalen Kammerdruckbedingungen. Mitteilungen aus dem Geologisch-Paläontologischen Institut de Universität Hamburg, 88: 51-62.
• Kiselev D. N. and Rogov M. A. 2004. Preliminary report on the Callovian/Oxfordian boundary in the Central Russia. In: 32nd International Geological Congress, electronic version posted on-line on July 20, 2004, Abstract Volume, pt. 1, abs. 177-19, 824.
• Kiselev D. N. and Rogov M. A. 2005. Zones, subzones and biohorizons of the Upper Callovian and Lower Oxfordian of the European part of Russia. In: Zakharov V. A., Rogov M. A. and Dzyuba O. S. (Eds), Materials of the First All-Russian Conference “Jurassic System of Russia: problems of stratigraphy and paleogeography”, Moscow, 128-134.
• Ogg J. G. 2004. The Jurassic Period. In: Gradstein F. M., Ogg J. G. and Smith A. (Eds). A geologic time scale 2004, 307-343. Cambridge, University Press. UK.
• Rogov M. A. and Egorov E. Yu. 2003. Polymorphism in the some Early Oxfordian oppeliids (Ammonoidea) of the Russian Platform. In: Bogdanov N. A., Vasil’eva T. I., Verzbitsky V. E. et al. (Eds.). Modern questions of geology. Materials of the 3rd Lectures in Memory of Yanshine, March 26-28, 2003, 245-248.