黑龙江省东部鸡西盆地早白垩世滴道组的沟鞭藻类

EARLY CRETACEOUS DINOFLAGELLATES FROM THE DIDAO FORMATION IN THE JIXI BASIN, EASTERN HEILONGJIANG PROVINCE,NE CHINA

首次描述鸡西盆地滴道组的沟鞭藻化石 2新种 :Lagenorhytisgranorugosussp .nov .和Vesperopsisdi daoensissp .nov .;讨论沟鞭藻组合特征、地质时代及沉积环境 ;认为滴道组含沟鞭藻化石的层段的时代为早白垩世早期 ,很可能为Berriasian—Valanginian期。沟鞭藻化石证实 ,在早白垩世早期滴道组沉积时 。

The Didao Formation, distributed in the Jixi Basin in the southeastern Heilongjiang Province, is a uite of continental coal bearing strata with a thickness of 200—300 m, mainly composed of conglomerate, sandstone, siltstone intercalated with thin coal layers and a little volcano clastic rocks. The type section lies in the Northern Nuanquan Mountain in Didao mineral district in Jixi. The lithologic character of the two dinoflagellate bearing samples from the standard section of the Didao Formation is respectively grayish black muddy siltstone and grayish green siltstone. Two new species of dinoflagellates, Lagenorhytis granorugosus sp. nov. and Vesperopsis didaoensis sp. nov., are described and illustrated. The dinoflagellate assemblage consists only of relatively more ceratioid Vesperopsis, and rare gonyaulacoid Lagenorhytis and cf. Apteodinium , lacking acritarchs and fresh water chlorophytes. The palaeoecological data and the assemblage characteristics of the two dinoflagellate genera indicate a sedimentary environment of slightly brackish to brackish water, which confirms that the Jixi Basin might be influenced by sea for a short time during the deposition of the Didao Formation in early Early Cretaceous. The research on the Didao Formation has a history of over half a century in China. Most scientists regarded the Didao Formation as Middle—Upper Jurassic in age before. According to the stratigraphic distribution of Vesperopsis and Lagenorhytis in the North Hemisphere and the age of the overlying strata (i.e.the Chengzihe Formation, Late Valanginian—Middle Barremian) of the Didao Formation (He Cheng quan et al .,2000),the age of the Didao Formation is regarded as early Early Cretaceous, probably Berriasian-Valanginian.