Historical distribution patterns of trigonioidids (non-marine Cretaceous bivalves) in Asia and their palaeogeographic significance
The non-marine trigonioidid bivalves show five phases of radiation in the Cretaceous of Pal-Asia: pre-Aptian (?Valanginian/Hauterivian–Barremian), Aptian, Albian, Cenomanian and Turonian–Maastrichtian. Their distribution patterns show two distinct palaeo-river systems feeding trigonioidids. Before the Cenomanian, the river system occupied the southwestern–southern–southeastern Pal-Asian continental margin areas. During the Turonian–Maastrichtian, it extended along the line of southcentral China−eastern China−northeastern China−northern China and Mongolia−northwestern China–eastern Fergana Basin of Kyrgyzstan−western Tajikistan Basin of Tajikistan–Tashkent area of Kazakhstan−central Kyzylkum of northern Uzbekistan–Aral Sea area of Kazakhstan. Furthermore, the general trigonioidid distribution pattern demonstrates that Japan was probably attached to part of eastern China and/or Korea during the ?Valanginian/Hauterivian–Cenomanian stages.
本邦下部白堊系産の新イシガヒ類Unio(Nippononania) ryosekiana (新亞屬・新種)
最近長尾巧教授より贈與された領石群層産の貝化石2箇を研究した所, 外形及び殻齒はUnio屬, 特に東亞産U., douglasiae GRIFFITH and PIDGEON群のものに一致するが, 殻表の放射状彫刻は狹義のUnio屬のものとは著しく異り, 寧ろHyriinaeに屬する南米産諸屬Diplodon, Prisodon等, もしくは朝鮮・滿洲の下部白堊系産Trigonioides kodairai KOBAYASHI and SUZUKIのそれに酷似することを知った。又 Parreysia屬のあるものも本化石に類似した放射状彫刻を有することがあるが, 通常外形及び殻齒によって容易に區別される。よって本化石に基いてUnio屬中に1新亞屬を設立し, 此化石種をUnio (Nippononaia) ryosekiana SUZUKI, 新亞屬・新種,と命名する。尚此化石の産地は, 徳島縣羽ノ浦町古毛か山中地溝帶中か不明になったとのことであるが, 何れにせよ下部白堊系物部川統の下部, 所謂領石群層中に産したものであることだけは確であらう。
Studies on the Early Cretaceous Longzhaogou and Jixi Groups of eastern Heilongjiang, northeast China, and their bearing on the age of supposedly Jurassic strata in eastern Asia
Abstract The coal-bearing Longzhaogou and Jixi Groups in eastern Heilongjiang, northeast China, consist of alternating marine and non-marine deposits containing abundant marine animal and plant fossils. The Jixi Group also yields members of the Johel Fauna that is widely distributed in northern and eastern China. The two groups have been considered as Jurassic or mainly Jurassic in age for a long time. However, recent studies documented that the ammonites, bivalves, dinoflagellates, angiosperms and sporopollens are all of Early Cretaceous rather than Jurassic age. It has been demonstrated that: (1) the Longzhaogou and Jixi Groups and their equivalents, the Johel Group of China and the Transbaikalian Group of Russia, are of Early Cretaceous age, (2) the Barremian-Albian was also a very important period of coal accumulation in northeastern China and perhaps in all of eastern Asia, (3) there existed a large shallow embayment connecting with the Palaeo-Pacific in eastern Heilongjiang, and it was the climate of the embayment that controlled the origin and development of the animal and plant communities of northeastern China during the Early Cretaceous. Correlation between formations in the Jixi and Longzhaogou Groups has also been revised in this paper.