西藏拉萨、纳木湖地区早白垩世阿普弟期菊石

EARLY CRETACEOUS APTIAN AMMONITES FROM LHASA AND NAM LAKE AREAS, XIZANG (TIBET)

一、前言1981年作者随中、法西藏地质科学考察队,并同王思恩等同志对拉萨、林周地区的白垩纪地层测制了剖面,采集了化石.

The ammonoids described here were collected from the middle part of the Takena Formation at the Yuanyang Mountain of the Poindo Farm and from the Xizhashan Formation of the Nam Lake area. The Takena Formation contains Acanthohoplites cf. uhligi, Parahoplites melchioris, etc., among which A. uhligi is a member of the L. Albian of the Caucasus, but it is also a member of the U. Aptian of Madagascar, while Parahoplites melchioris is the typical member of the U. Apt. of the Caucasus, indicating that the Takena Formation is referred to the Aptian-Albian. The Xizhashan Formation contains Pseudohaploceras cf. douvillei, P. cf. leptoviensis, P. sp. 1, P. sp. 2, etc., among which P. douvillei is a member of the L. Apt. of the Caucasus, while P. liptoviensis is a member of the Aptian of France. Based on the ammonoid fauna, the Xizhashan Formation belongs to the Aptian or Aptian to Albian. Both of the Takena Formation and the Xizhashan Formation may be correlated with the Zhawangzi Formation of the Yamzho Yum Lake, the Guco V Formation of Nyalam Guco, the Dzong sandstone member (L. Apt.) of the Chuck Formation in Nepal, the Ukra Formation in Kachchh and the Habur Formation in Jaisalmer.