Stratigraphy and fossil fauna of the marine Triassic System in Russian Far East

2005年、2006年和2007年对俄罗斯南滨海地区下三叠统地层和古生物学进行了深入研究。下三叠统由高到低分为Lazurnaya组和Zhitkov组。Lazurnaya组不整合覆盖二叠纪岩石，由基底砾岩和浅海相砂岩组成，具有丘状交叉分层。日特科夫组主要由近海滑塌黑色泥岩和浊积砂岩组成。整个层序中均有丰富的菊石，从上下Induan（upper Griesbachian）到上下Olenekian（upper Smithian）先后划分出几个菊石带。印度河菊石包括华南和加拿大共有的几种，但大多数下奥仑阶菊石是特有种。这一事实表明，在奥勒涅纪早期，菊石具有区域性多样性。在印度洋发现了4属鹦鹉螺类5种。它们具有渐开线、渐开线和回旋形的不同壳形，以及从中心到腹侧的不同虹吸位置。它们属于同一科，很可能是在早三叠纪的P/T灭绝事件中从单一祖先迅速分化而来的。南滨海地区鹦鹉螺多样性最高。这一事实表明，南滨海边疆区鹦鹉螺的恢复速度要比其他地区快得多。

The stratigraphy and paleontology of the Lower Triassic in South Primorye, Russia were thoroughly investigated in 2005, 2006 and 2007. The Lower Triassic is divided into the Lazurnaya and Zhitkov formations in ascending order. The Lazurnaya Formation unconformably covers the Permian rocks, and consists of basal conglomerate and shallow marine sandstones with hummocky cross stratification. The Zhitkov Formation is composed mainly of offshore black mudstone with slump deposit and turbiditic sandstone. Ammonites are abundant throughout the sequence, in which several ammonite zones were recognized successively from upper Lower Induan(Upper Griesbachian) to upper Lower Olenekian(Upper Smithian). The Induan ammonites include several species in common with South China and Canada, but the most Lower Olenekian ammonites are endemic species. This fact suggests that ammonites diversified regionally during the early Olenekian. Five species belonging to four genera of nautiloids were discovered from the Induan. They show a various shell form from involute, evolute and gyroconic coiling, and various siphuncle position from center to ventral. They belong to the same family, and it is very likely that they rapidly diversified from single ancestor survived at P/T extinction event during the early Triassic. The nautiloid diversity was the highest in the South Primorye. This fact suggests that the recovery of the nautiloid in South Primorye was much faster than the other area.