东亚地区松辽盆地和美洲大陆北美西部海道的晚白垩纪气候变化记录

王成善

摘要：地质历史上的地球并不都是与我们现在生活的冰室地球（间冰期）相同，而是表现出“温室状态”与“冰室状态”交替出现的周期性。地质记录显示，显生宙70%时间地球赤道到两极经向温度差还不到现在的一半，并缺乏显著的大陆冰川作用。科学界普遍认为，温室状态下气候、海洋都遵循着与现在不同的运行模式。了解和探索温室地球下地球气候的变化机制与其对生物圈的影响，无论对于认识过去、还是预测未来都尤为重要。海洋和陆地构成了气候系统演化中两个既相互联系又相对独立的单元。要全面深刻地理解晚中生代温室地球不同时间尺度的古气候变化，关键在于获取海洋和陆地连续、完整的地质记录，利用有效的古气候、古环境替代性指标，进而开展古气候与古环境的重建。在国际地球科学计划项目（IGCP555）和国家973支持下，本研究对东亚地区松辽盆地和美洲大陆北美西部海道的白垩纪古气候数据进行了对比研究，综合了白垩纪海相和陆相沉积记录的古气候数据，大大促进我们对白垩纪温室气候变化的理解，并可能对应对现今全球变暖的挑战提供帮助。

关键词：晚白垩世；古气候；西部海道；松辽盆地；陆相和海相沉积响应；温室地球

Late Cretaceous climate changes recorded in Eastern Asian lacustrine deposits and North American Epieric sea strata

Abstract：Cretaceous climate data of the long-lived Cretaceous Songliao Basin （SB） in eastern Asia is correlated and compared with the Western Interior Seaway （WIS） on the northern American plate， in order to understand better the dynamics of the Earths past ‘greenhouse climates. Nearly continuous Late Cretaceous terrestrial deposition in the Songliao Basin is represented by two cores totaling 2431 m in length. The Turonian–Maastrichtian age of the section is based on integrated stratigraphy， and is comparable in agewith Upper Cretaceous strata in the WIS. Being consistent with global trends， the dynamic Late Cretaceous climates of both the SB and WIS gradually cooled from the warmest Albian–Cenomanian time to the end of the Maastrichtian with several intervening warm periods as did the global climate. However regional differences existed， the Songliao Basin climate was humid to semi-humid， warm temperate–subtropical and the Western Interior Seaway was in the humid， warm temperate zone and experienced only moderate climatic changes. The shifts of oxygen isotope data in the Songliao Basin were frequent and abrupt， whereas WIS records more gradual change affected mainly by fresh-water runoff mixingwith southern Tethyan and northern Arcticwaters. Sedimentary cycles of eccentricity， obliquity and precession bands are recorded in both the SB and WIS basins. The sedimentary cycles in the WIS and SB are interpreted to be related to variations of the wet/dry runoff cycles， which indicate that orbital forcing played an important role in global climate change in Late Cretaceous. The most favorable condition for organic carbon burial in both the SB and WIS basin was bottom water anoxia regardless of the cause of the anoxia. But the organic carbon burial rate was usually much higher in the Songliao Lake than in the WI epeiric sea suggesting that giant lakes may serve as important sinks of atmospheric CO2. In both basins organic-rich deposits formed during a rise in water level and incursion of saline waters. The integration of paleoclimate data from Cretaceous marine deposits and terrestrial sedimentary record will promote our understanding of the Cretaceous ‘greenhouseclimate change and may provide insights for a future greenhouse world.

Keywords：Late Cretaceous；Paleoclimate；Western Interior Seaway；Songliao Basin；Correlation of terrestrial and marine deposits；Greenhouse world

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