粤北丹霞盆地白垩系长坝组的介形类动物群

CRETACEOUS OSTRACODS FROM THE CHANGBA FORMATION IN THE DANXIA BASIN OF NORTHERN GUANGDONG PROVINCE

粤北丹霞盆地白垩系长坝组产介形类化石 15 属 50 种,笔者描述其中 15 属 47 种(包括 3 个新种)。长坝组介形类动物群可以划分两个化石组合:( 1 ) Mongolocypris-Cypridea-Darwinula 组合,分布长坝组二段,属种繁多, 组合特征明显,与松辽平原泉头组 - 姚家组、湖北贾店组、浙江兰溪组等的介形类面貌相似,可以大致对比,由于出现少量晚白垩世标志化石 Talicypridea 属和大个体的 Mongolocypris 属,反映它与晚白垩世介形类的关系更为密切,但又不同于晚白垩世中晚期的南雄群 Talicypridea 动物群,层位偏低,时代较早,属晚白垩世早期为宜,大致相当于赛诺曼期( Cenomanian );( 2 ) Cypridea-Altanicypris-Candona 组合,分布长坝组四段,其层位在长坝组二段之上,晚白垩世丹霞组之下,组合中富含类女星介科的 Altanicypris 属,许多属种出现在晚白垩世地层中,其时代属晚白垩世无疑,与土仑期( Turonian )大致相当。

The Cretaceous ostracods were collected from 39 sample of borehole and outcrop of the Changba Formation in the Danxia Basin,northern Guangdong Province. Totally 50 ostracod species in 15 genera have been recognized,and out of which 47 species in 15 genera are figured herein,including 3 new species described. The ostracod fauna is subdivided into 2 assemblages： （1）Mongolocypris-Cypridea-Darwinula assemblage, from the Member 2 of Changba Formation. This assemblage is very similar to that yielded from the Quantou-Yaojia Formation of the Songliao Basin,the Jiadian Formation in Hubei Province, the Lanxi Formation in Zhejiang Province, and therefore they are also close to each other in geological age. It is obviously different from that of the middle-late Irate Cretaceous of the Nanxiong Basin. The most common genera are Mongolocypris, Cypridea and Darwinula. The former reached its most flourishing state,large individual size,displaying a high diversity and a large quantity, with less appearances of the genus Tali- cypridea. Talicypridea is the index fossil for the middle-late Late Cretaceous in the Far East. Most of its known taxa are frequantly seen during the Late Cretaceous in China, while a few are extensively distributed in the Early Cretaceous. According to the features of ostracod,the Member 2 of the Changba Formation could be assigned to the early Late Cretaceous（i. e. Cenomanian）. （2） Cypridea-Altanicypris-Candona assemblage, from the Member 4 of Changba Formation, which belongs to the middle Late Cretaceous（i. e. Turonian）.