非海相白垩系年代学和对比

从1800年代初最早确定的白垩系定义起,白垩系就包括了海相和非海相白垩纪的地层和化石。白垩纪是一个全球性气候温暖、海平面高、构造和火山活动强烈的世界。此时,多块大陆分解,几乎所有海洋都已打开,形成了与现代相近的海陆分布的地理图案。这一变革导致了全球生物群的区域化,给全球对比带来了困难。白垩纪的全球年代地层表是主要依据菊石和微体生物(有孔虫和钙质超微浮游生物)化石,并与已完整建立的全球极性倒转年表和很多放射性同位素年龄相结合的产物。从孢粉到恐龙等各类非海相化石均已用于白垩纪生物地层学。此期专刊的特色是聚焦于区域或全球的孢粉(包括沟鞭藻)、大植物、甲壳类(包括叶肢介和介形类)、软体动物(包括腹足类和双壳类)和脊椎动物(包括硬躯体和足印)非海相白垩纪生物地层学和生物年代学。这些研究大大扩展了非海相白垩系对比的内容,并强调了将能取得更多进展的研究方向。非海相地层和化石群中直接夹有海相地层和化石的剖面/地区的非海相生物地层学更精确的研究,高分辨率的微体化石,特别是既出现于非海相又见于海相地层中的微体化石的微体生物地层学的进展,更多的直接与非海相生物地层学相关的放射性同位素和古地磁年龄的测试,非海相地层的高分辨率层序和旋回地层学分析及与非海相生物地层学对比的化学地层学的发展等,均将促进全球非海相白垩纪地层时代和对比,甚至以国际地质时标为准绳的全球非海相白垩纪地层对比框架表的建立。

NON-MARINE CRETACEOUS CHRONOLOGY AND CORRELATION

From the first definition of the Cretaceous System in the early 1800s,the Cretaceous has included both marine and non-marine Cretaceous strata and fossils.The Cretaceous was a world of global greenhouse,high sea level,and intensive tectonic and volcanic activity,during which the remaining world oceans opened and the continents diverged to attain relatively modern configurations.This produced a provincialization of the global biota that makes global correlations challenging.The Cretaceous standard global chronostratigraphic scale is based primarily on ammonoids and microfossils(foraminiferans and calcareous nannoplankton) integrated with a well-established global polarity timescale and a relative abundance of radioisotopic ages.All groups of Cretaceous non-marine fossils have been used in Cretaceous biostratigraphy,from sporo-pollen to dinosaurs.This special issue features regional and global studies of Cretaceous non-marine biostratigraphy and biochronology that focus on sporo-pollen,including dinoflagellates,megafossil plants,crustaceans(conchostracans and ostracods),molluscs(gastropods and bivalves) and vertebrates(both hard-partbody fossils and footprints).These studies substantially augment non-marine Cretaceous correlations and underscore the ways in which further progress can be made.Better establishing non-marine biostratigraphy where non-marine strata and fossils are directly intercalated with marine strata and fossils;advances in high-resolution microfossil biostratigraphy,especially of microfossils that co-occur in non-marine and marine strata;more radioisotopic ages and palaeomagnetic dating that can be directly related to non-marine biostratigraphy;analysis of high resolution sequence and cycle stratigraphy in non-marine strata;and further development of chemostratigraphy correlated to non-marine biostratigraphy—will all promote the establishment of non-marine Cretaceous stratigraphic ages and correlation and even promote establishing a non-marine Cretaceous stratigraphic framework chart in the global timescale.