東亞地區松遼盆地和美洲大陸北美西部海道的晚白堊紀氣候變化記錄

王成善

摘要：地質歷史上的地球并不都是與我們現在生活的冰室地球（間冰期）相同，而是表現出“溫室狀態”與“冰室狀態”交替出現的周期性。地質記錄顯示，顯生宙70%時間地球赤道到兩極經向溫度差還不到現在的一半，并缺乏顯著的大陸冰川作用。科學界普遍認為，溫室狀態下氣候、海洋都遵循著與現在不同的運行模式。了解和探索溫室地球下地球氣候的變化機制與其對生物圈的影響，無論對于認識過去、還是預測未來都尤為重要。海洋和陸地構成了氣候系統演化中兩個既相互聯系又相對獨立的單元。要全面深刻地理解晚中生代溫室地球不同時間尺度的古氣候變化，關鍵在于獲取海洋和陸地連續、完整的地質記錄，利用有效的古氣候、古環境替代性指標，進而開展古氣候與古環境的重建。在國際地球科學計劃項目（IGCP555）和國家973支持下，本研究對東亞地區松遼盆地和美洲大陸北美西部海道的白堊紀古氣候數據進行了對比研究，綜合了白堊紀海相和陸相沉積記錄的古氣候數據，大大促進我們對白堊紀溫室氣候變化的理解，并可能對應對現今全球變暖的挑戰提供幫助。

關鍵詞：晚白堊世；古氣候；西部海道；松遼盆地；陸相和海相沉積響應；溫室地球

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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