Lower Jurassic ammonite geologic time scale of Northeast Asia

Abstract

Типовое местонахождение. Северо-Восток Азии. Левый борт долины р. Кедон, непосредственно ниже устья р. Омкучан (Омолонский массив). Границы. Нижняя граница зоны проводится по появлению вида-индекса. Состав. В объеме зоны выделяются (снизу вверх) подзоны Psiloceras planorbis, Lenopsiloceras olenekense и слои с Transipsiloceras armanense, непосредственная смыкаемость между которыми отсутствует. Подзона P.planorbis сопоставляется с одноименной подзоной в основании геттанга Англии (K.N. Page, 2003). Кроме вида-индекса (табл. I, фиг. 1) присутствуют Pleuropsiloceras viligense (Chud. et Polub.) (табл. I, фиг. 2). Kolymophylloceras turomchense Repin (табл. III, фиг.9), Platyphyllocers okhoticum Repin (табл. II, фиг. 7). Подзона planorbis установлена в

New Data on Stratigraphy of the Jurassic (Pliensbachian–Aalenian) Sediments of the Cape Tsvetkov Region, Eastern Taimyr

“…marchaensis in the section of the Viliga River originates from the sequence with ammonites Pseudolioceras replicatum Buckm., and the sequences with Pseudolioceras beyrichi and Pseudolioceras maclintocki were found to contain Propeamussium olenekense and Oxytoma jacksoni (Repin and Polubotko, 2015). In the modern ammonite scale of northeastern Russia, the species Pseudolioceras replicatum indexes the terminal Toarcian zone (Repin, 2016). From this, it follows that the stratigraphic framework of the beds with Oxytoma jacksoni and Propeamussium olenekense covers the upper Toarcian zone and the lower Aalenian zone in the north of Russia.…”

“…The correlation of the boreal lower Aalenian with the European standard is the subject of discussion (Knyazev et al, 2007;Repin, 2016). According to the modern ideas, the lower Aalenian in Eastern Siberia is regarded in the framework of the Pseudolioceras maclintocki Zone, where at the base the beds with P. beyrichi are recognized (Shurygin et al, 2011;Zakharov et al, 1997).…”

“…Over the last three decades, the zonal scales of the Toarcian Stage were developed for Eastern Siberia and northeastern Russia on the basis of ammonites, bivalves, and microfauna (Knyazev, 1991;Knyazev et al, 2003;Nikitenko, 2009;Repin, 2016;Repin and Polubotko, 1993;Sapjanik, 1991а, 1991bShurygin et al, 2011). In accordance with the most complete analytical record of the Jurassic stratigraphy for Sibe- 1 In the first half of the 20th century, Toarcian ctenodontides of Siberia were named Leda acuminata (Goldf.)…”

The late Pliensbachian (Early Jurassic) ammonoidAmaltheusin Japan: systematics and biostratigraphic and paleobiogeographic significance

“…1, figs. 9, 14, with synonymy.2016 Amaltheus ( Amaltheus ) stokesi ; Repin, p. 37, figs 4, 5.2016 Amaltheus stokesi ; Nützel et al, p.3, fig. 2.

Figure 4. Amaltheus stokesi from Japan.

…”

“…Amaltheus sensibilis Dagis, 1976 and A. subbifurcus Repin, 1968 were both collected from the Northeast Russian region (Repin, 1974, 2009, 2016; Dagis, 1976) and are distinguished from A. stokesi by the larger umbilicus and stronger projection of the ribs in the ventrolateral part.…”