摘要
已经报道的北美西部陆相白垩系-古近系界线剖面已达近百处,这些剖面分布在阿拉斯加南部向南经加拿大直到美国南部的新墨西哥州北部的广大北美西部内陆地区,其中很多属迄今所知全球很好的陆相白垩系-古近系界线剖面。这些剖面常有标志性的界线黏土,并伴有其他地球化学、生物地层学特征。因为这些剖面所在地当时都在湿润或半干旱地区内,有利于生物化石,特别是孢粉化石的保存,易于开展孢粉学研究。经过近四十年不懈努力,孢粉学已经成为北美精确确定陆相白垩系-古近系界线最重要的、也是迄今为止所知最为有效的古生物学工具。孢粉植物群在界线上下特征差别显著,容易区分。界线之下含有大量主要繁盛于白垩纪的被子植物花粉,而在临近界线时则突然消失或仅零星出现,界线附近则以一层孢子异常丰富层为古近系底部特征。进入古近纪之后,虽然被子植物花粉有所恢复,但是繁盛于白垩纪的成分却很少出现。北美和新西兰、日本白垩系-古近系界线附近在沉积岩和孢粉学方面的相似性表明这一事件可能是全球性事件。简要回顾和讨论了我国与孢粉学相关的几个热点地区陆相白垩系-古近系界线的研究概况,我国东北及江苏北部和北美西部大部分地区白垩系-古近系界线附近的孢粉植物群及其沉积环境比较类似,在苏北到东北地区范围内首次发现陆相白垩系-古近系界线地层的可能性比其他地区大。
The Cretaceous-Paleogene boundary in terrestrial settings is best known and documented for the interior part of North America where nearly 100 sites have been studied to date. The vast majority of these sites occur in a humid facies setting that apparently favours the preservation of the boundary elaystone. Palynological studies are extensive from areas of New Mexico northwards into Alaska. The best-preserved sections have a boundary claystone along with one or more geochemical and biostratigraphic anomalies. Many similarities appear to exist between the North American sites and terrestrial sites described from New Zealand and Japan, suggesting that the boundary events were global in extent in relation to the palynological characters. Scientists have endeavored in searching for Cretaceous-Paleogene boundary in China for several decades. To date, no convincing boundary sites are known in China, but there is a potential for them to exist there. The area with good potential for direct comparisons to the North American assemblages lies in Heilongjiang, Northern Jiangsu and the neighbouring areas where the assemblages appear similar to those seen in North America.
出处
《地层学杂志》
CSCD
北大核心
2009年第1期18-34,共17页
Journal of Stratigraphy
基金
国家自然科学基金(N0.40072009)资助
关键词
生物地层
孢粉化石
白垩系-古近系界线
北美
中国
biostratigraphy, palynology, Cretaceous-Paleogene boundary, North America, China
