摘要： 晚白垩世河道和冲积平原等河流相沉积广泛分布于中国大部分地区,保存了大量以鸭嘴龙超科为主的恐龙骨骼化石和遗迹化石。这些河流是否存在水系上的联系以及其对陆地生态系统分布的影响程度,目前研究较少。笔者收集了中国9个晚白垩世陆相盆地共2357个碎屑锆石的U-Pb年龄资料,通过对已收集的碎屑锆石的物源分析,探讨了中国晚白垩世的水系展布模式和物源方向。研究结果表明:晚白垩世中国南方地区可能存在北东—南西向的大型水系,其与现代水系展布模式相反,整体流向可能起源于晚中生代东部高原,向西和西南方向流经中国南方大部分地区,并形成了彼此相互交错、宽阔的河岸和冲积平原带;而北方地区的盆地则显示出被古隆起分隔的山间盆地特征,除共享来自晚中生代东部高原的少量物源外,各个盆地的物源主要来自于周围的古隆起,并形成了较为独立的复杂水系。以鸭嘴龙超科为代表的恐龙主要繁盛于北方地区相对独立的水系所形成的流域,演化出独特的东亚鸭嘴龙超科动物群。南方大型水系所形成的流域虽然保存了大量恐龙蛋和足迹化石,但仅发现少量骨骼化石,推测这可能是因为以鸭嘴龙为主的恐龙不适宜在南方炎热干旱的气候条件下常年生活,而只是在适宜的季节沿南方大型水系迁徙或繁殖。

关键词: 晚白垩世, 物源, 水系分析, 恐龙, 生物古地理

Abstract: The Upper Cretaceous in China is featured by fluvial deposits,such as channels and floodplains,in which abundant hadrosaur-dominated dinosaurs and dinosaur trace fossils are preserved. Whether these Late Cretaceous fluvial deposits belonged to certain large-scale paleoriver systems or not,and how the distribution pattern of paleoriver systems affected the evolution of terrestrial ecosystems,have not been well studied. In this paper,U-Pb ages of 2357 detrital zircons from nine Late Cretaceous terrestrial basins in China are collected. Based on provenance analysis on these detrital zircons,the distribution pattern of the Late Cretaceous paleoriver systems and provenance directions are discussed. The results show that there existed SW-NE oriented,large-scale river systems in southern China in the Late Cretaceous. Contrary to the eastward and southeastward drainage directions of modern river systems,the Late Cretaceous paleoriver systems drained from an inferred coastal plateau in eastern China to the west and southwest,and resulted in widespread web-like riverbank and floodplain deposits in southern China. In contrast,basins in northern China were separated by paleo-uplifts,from which most of the sediments were derived. The drainage systems of the studied basins in northern China were largely independent from each other. These complex drainage basins in northern China created many isolated habitats where a unique East Asia hadrosaur fauna evolved. In contrast,the riverine deposits of the river systems in southern China are featured by fossils of dinosaur eggs and footprints,and only few dinosaur skeleton fossils. This feature probably resulted from the hot and arid climate in southern China,which was not suitable to hadrosaur-dominated dinosaurs as a perennial habitat. They instead may have migrated through or laid eggs along the river systems seasonally.

Key words: Late Cretaceous, provenance, paleoriver analysis, hadrosaur, palaeobiogeography

中图分类号: 

• P531