松辽盆地晚白垩世介形类古生态学

通过化石组合和岩性指标分析松辽盆地上白垩统自下而上青山口组—姚家组—嫩江组一段介形类的古生态学。青山口组盐度具有偏咸性、微咸性到半咸性的变化,32个介形类种以栖居于温暖湿润气候带的浅湖微咸水类型占绝对优势,水体清澈安静,有机质丰富,底质为泥等细粒沉积物(个别的为粉砂沉积物),宜于介形类动物群生长且有利于壳体完好保存;其次为生活于半咸水的深湖—半深湖类型,底质为泥。姚家组—嫩江组一段见23个介形类种,栖居于温暖半湿润气候带,以半咸水的深湖、半深湖—浅湖区的类型为主,多泥底,偶见粉砂质底;其次为微咸水的浅湖—三角洲前缘型,泥或粉砂质底;仅3个种生活于温暖湿润的粉砂质底淡水浅湖区。温暖湿润的淡水三角洲分流平原带则难以产出介形类化石。

PALAEOECOLOGY OF THE UPPER CRETACEOUS OSTRACODS FROM THE SONGLIAO BASIN,NORTHEAST CHINA

Ostracode faunal and lithological analyes disclose the paleoecology of the Upper Cretaceous lacustrine sequences of the Qingshankou Formation, Yaojia Formation and Member 1 of Nenjiang Formation in the Songliao Basin. 32 species are recognized from the Qingshankou Formation, which illustrates the fluctuation of palaeosalinity, low turbidity and rich in nutrition. Most of them inhabited within shallow, warm and humid lake belt with muddy-rich and less silty substrate. These environmental indexes did benefit the thriving of the ostracode fauna and well preservation of their shells. 23 species from the Yaojia Formation and the Member 1 of Nenjiang Formation imply a warm and semi-humid setting. Most species inhibited in a range from deep, semi-deep to shallow lake belts with muddy-dominated and less silty substrata; and only three species are limited to a warm, humid shallow lake with silty substrate. However, split-flow plain of the fresh water delta with warm and humid background is not favorable for the occurrence of the ostracode fauna.