黑龙江省东北部绥滨地区东荣组最上部的沟鞭藻组合--兼论该地区侏罗-白垩系界线

黑龙江省东北部绥滨地区海相东荣组最上部产丰富或较丰富的沟鞭藻类，经鉴定达20属30余种，其中有些在我国为首次发现，包括一新种Leberidocysta suibinensis sp．nov.。文中详细地讨论沟鞭藻Oligosphae-ridium pulcherrimum组合的特征及其地质时代，包括侏罗-白垩系界线等；认为该组合的时代为Berriasian—Valanginian期。这一组合是我国白垩纪最早期的海相沉积，也是白垩系底部的第一个化石组合；首次提出黑龙江省东北部绥滨地区侏罗-白垩系界线应置于Tithonian阶的沟鞭藻Amphorula delicata组合与Berriasian-Valanginian阶的Oligosphaeridium pulcherrimum组合之间，即岩石地层上的东荣组上部与最上部之间。这条沟鞭藻类生物地层界线与双壳类的下、中伏尔加阶的Buchiamosquensis-B．rugosa带与上伏尔加阶的B．fischeriana带之间的分界完全吻合，与目前国际地科联地层委员会建议的侏罗-白垩系界线位于中伏尔加阶与上伏尔加阶之间亦完全一致。

DINOFLAGELLATE ASSEMBLAGE FROM THE UPPERMOST PART OF THE DONGRONG FORMATION WITH DISCUSSION ON JURASSIC-CRETACEOUS BOUNDARY IN SUIBIN AREA, NORTHEASTERN HEILONGJIANG PROVINCE, NE CHINA

The Dongrong Formation previously considered Late Jurassic in age, distributed in the Suibin area of northeastern Heilongjiang Province of NE China, is a unit of continuous shallow marine clastic sediments with a maximum thickness of about 395 m. It may be divided into two parts, the lower part consisting of dark grey and black siltstones intercalated with some tuffbeds, and the upper part composing of grey and dark green fine grained sandstones intercalated with tuffs. Sun Xue kun and He Cheng quan(1992)reported abundant marine dinoflagellate fossils from both parts of the formation. A rich and diverse dinoflagellate cyst assemblage dealt with in this work is obtained from the uppermost part of the Dongrong Formation of seven boreholes in the area. It is composed of at least 19 genera and 30 species with 1 variety of dinocysts, 1 genus 1 species of acritarchs, of which 21 species with 1 variety of dinoflagellates are described and illustrated, including one new species,Leberidocysta suibinensis sp.nov.