Vasily MITTA

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Zoologisch-Botanische Datenbank/Zoological-Botanical Database

Digitale Literatur/Digital Literature

Zeitschrift/Journal: Berichte der Geologischen Bundesanstalt

Jahr/Year: 2008

Band/Volume: 74

Autor(en)/Author(s): Mitta Vasily

Artikel/Article: The Berriasian (=Ryazanian) Stage of the Russian Platform: The First Cretaceous Invasion of Tethyan Ammonites 76-77 ©Geol. Bundesanstalt, Wien; download unter www.geologie.ac.at

- 76 - Berichte der Geologischen Bundesanstalt, ISSN 1017- 8880, Band 74, Wien 2008 ______

THE BERRIASIAN (=RYAZANIAN) STAGE OF THE RUSSIAN PLATFORM: THE FIRST

CRETACEOUS INVASION OF TETHYAN AMMONITES

Vasily MITTA

The first Cretaceous invasion of Tethyan phylogenetic line through several generations ammonites on the Russian platform is usually of taxa. The first representatives of Riasanites explained by paleogeographic reorganizations (R. swistowianus (Nikitin)) appeared in Central which have opened seaways from the Northern Russia, and there are no positive records of Caucasus through Mangyshlak to Central this species in other regions. The specimens Russia. The genus Riasanites Spath close to the R. swistowianus have been found, supposedly played an important role in this infrequently, only in Mangyshlak. The revision invasion as the majority of researchers regards of Riasanites (Mitta, in press), has shown that the Central Russian Riasanites as migrants the North Caucasian members of this genus from the Northern Caucasus (Sazonova, 1971; belong to R. maikopensis (Grigorieva), and the Sey & Kalacheva, 1997; and others). However, Crimean ones – to R. crassicostatus the ancestors of Riasanites have not been (Kvantaliani et Lyssenko). However, the "early" found in the Northern Caucasus, and the North Riasanites from the Northern Caucasus are Caucasian origin of this genus cannot be closer not to the early Riasanites from Russian supported. In contrast, Jeletzky (1984) platform, but, on the contrary, to the late suggested that the basin of the Oka River was morphs of R. rjasanensis (Nikitin). Therefore it the center of origin of Riasanites (from seem most likely that the ancestors of “Pavlovia-like Boreal perisphinctids”), where Riasanites migrated from the Western Tethys from they spread to the Northern Caucasus through the Polish (Brest) passage into the and the Crimea through the Peri-Caspian and Central Russian sea, where the genus Mangyshlak, and in a westward direction evolved. Later Riasanites spread up to the through the Polish strait to Poland. A weak basin of the Vyatka River in the north, and point of this theory is the absence of ancestors through Mangyshlak to the Northern Caucasus of Riasanites among the Boreal ammonites. to the Crimea, in the south. The morphology of the shell and the sculpture Transcaspiites Luppov is another genus from of Riasanites show their undoubtedly “Tethyan” the family Himalayitidae with a similar origin. Probably, they were direct descendant distribution – the Northern Caucasus, of Tithonian taxa. It is possible that the very Mangyshlak and Central Russia. The genus close resemblance of Riasanites and also included T. hundesianus (Uhlig) from the Corongoceras Spath (Himalayitidae) resulted Himalayas. Transcaspiites probably originated from closely related heterochronous in the Central Tethys, and later migrated to the homoeomorphy – similar morphological north – to the Caucasus and then through characters are observed in the same Mangyshlak to Central Russia. This genus has

1st International Meeting on Correlation of Cretaceous Micro- and Macrofossils Vienna 16th – 18th April, 2008 ©Geol. Bundesanstalt, Wien; download unter www.geologie.ac.at

Berichte der Geologischen Bundesanstalt, ISSN 1017- 8880, Band 74, Wien 2008 - 77 - ______not been recorded from the Crimea or Western opening of the narrow Polish Strait in the West Europe. and a wide strait in the South-East, probably Another genus of Tethyan origin is coincided with the maximum of this Subalpinites Mazenot (Neocomitidae). This transgression at the beginning of the genus has been described from the Berriasian Rjasanensis time (earliest Ryazanian). These of France and has been recorded from straits were short-lived, as in the second half of Mangyshlak. Some species of Subalpinites, the Rjasanensis time the migration of (some as yet unpublished) are widespread in ammonites from the Western Tethys stopped, the Ryazanian Stage of the Russian platform. and the same happened to the exchange of The genus Subalpinites is practically unknown faunas with the Peri-Caspian Sea. The records in the Crimea and the Caucasus, except two of Marek (1967; and others) of ammonites small specimens from the basin of the Belaya similar to Riasanites in Poland (Kuyav), appear River (Northern Caucasus), probably belonging to be in agreement with the above theory. to this genus. Thus the migration of sub- This study is supported by the program of the Mediterranean Subalpinites through the Polish Presidium of the Russian Academy of passage into the Central Russian Sea and Sciences “The Origin and Evolution of the further on to the South-East – to Mangyshlak Biosphere” (project “Coevolution in the Marine seems very probable. Pelagic Biota and its Response to Abiotic The time of the opening of the Polish Strait is Changes in the Critical Epochs of the determined differently by different researchers, Paleozoic and Mesozoic”). from the Tzikwinianus chron of the Ryazanian up to Early Valanginian. Our data allow earlier dating of this event – to the Rjasanensis chron. The sea-regression maximum in Central Russia at the J/K boundary coincided with the first half of the Nodiger time (latest Volgian), and a new marine transgression had begun by its second half (the Milkovensis moment). The

Vasily MITTA Paleontological Institute of Russian Academy of Sciences Profsoyuznaya 123 Moscow 117997 Russia e-mail: [email protected]

1st International Meeting on Correlation of Cretaceous Micro- and Macrofossils Vienna 16th – 18th April, 2008