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松辽盆地白垩系嫩江组中除含丰富的介形类化石外,还含有丰富的叶肢介、瓣鳃类、腹足类、植物、轮藻、孢粉以及爬行动物、鱼化石等。因此,以某一门类化石为根据曾对其地质时代作过详细论述(表1)。多数研究者主张将该组归于晚白垩世,少数主张归于早白垩世,而介形类工作者,多数主张归于早白垩世。我们认为嫩江组的地质时代划为晚白垩世早期为宜,其理由为(表2):(1)含有一定数量的晚白垩世标志化石 Talicypridea=Cristocypridea。如 Talicypridea
The Cretaceous Nenjiang Formation in the Songliao Basin is rich in phylloid fossils and is also rich in leaf-limbs, valve gills, gastropods, plants, charophytes, spores, reptiles and fish fossils. Therefore, based on a certain category of fossils, the geologic age has been elaborated (Table 1). Most researchers advocated that the group should be attributed to Late Cretaceous, while a few advocated attributed to Early Cretaceous. However, most of the orthodox workers advocated attributed to Early Cretaceous. We think that the geologic epoch of the Nenjiang Formation is suitable for the early Late Cretaceous. The reason for this is as follows: (1) There is a certain amount of Late-Cretaceous fossil Talicypridea = Cristocypridea. Such as Talicypridea