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

2005年、2006年和2007年，对俄罗斯滨海边疆区下三叠统地层和古生物进行了全面调查。下三叠统自下而上分为Lazurnaya组和Zhitkov组。Lazurnaya组不整合地覆盖在二叠系岩石之上，由底砾岩和浅海相砂岩组成，具丘状交错层理。Zhitkov组主要由近海黑色泥岩和滑塌存款及浊积岩组成。整个层序中菊石十分丰富，从印度河上游（格里斯巴赫阶上游）到奥伦尼克阶上游（史密斯阶上游）相继发现了几个菊石带。印度纪的菊石包括几种与华南和加拿大相同的种类，但大多数下奥伦尼克纪的菊石是特有种。这一事实表明，菊石在奥伦尼克纪早期的区域多样化。在印度河发现鹦鹉螺4属5种。它们的壳形从内卷、渐屈、旋锥等多种多样，从中心到腹面的位置也各不相同。它们属于同一科，很可能是在早三叠世P/T灭绝事件中幸存下来的单一祖先迅速多样化的。鹦鹉螺的多样性是最高的南部滨海。这一事实表明，鹦鹉螺在南部滨海边疆区的恢复速度比其他地区快得多。

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.