東亞地區(qū)松遼盆地和美洲大陸北美西部海道的晚白堊紀(jì)氣候變化記錄

王成善

摘要：地質(zhì)歷史上的地球并不都是與我們現(xiàn)在生活的冰室地球（間冰期）相同，而是表現(xiàn)出“溫室狀態(tài)”與“冰室狀態(tài)”交替出現(xiàn)的周期性。地質(zhì)記錄顯示，顯生宙70%時(shí)間地球赤道到兩極經(jīng)向溫度差還不到現(xiàn)在的一半，并缺乏顯著的大陸冰川作用?？茖W(xué)界普遍認(rèn)為，溫室狀態(tài)下氣候、海洋都遵循著與現(xiàn)在不同的運(yùn)行模式。了解和探索溫室地球下地球氣候的變化機(jī)制與其對(duì)生物圈的影響，無論對(duì)于認(rèn)識(shí)過去、還是預(yù)測(cè)未來都尤為重要。海洋和陸地構(gòu)成了氣候系統(tǒng)演化中兩個(gè)既相互聯(lián)系又相對(duì)獨(dú)立的單元。要全面深刻地理解晚中生代溫室地球不同時(shí)間尺度的古氣候變化，關(guān)鍵在于獲取海洋和陸地連續(xù)、完整的地質(zhì)記錄，利用有效的古氣候、古環(huán)境替代性指標(biāo)，進(jìn)而開展古氣候與古環(huán)境的重建。在國(guó)際地球科學(xué)計(jì)劃項(xiàng)目（IGCP555）和國(guó)家973支持下，本研究對(duì)東亞地區(qū)松遼盆地和美洲大陸北美西部海道的白堊紀(jì)古氣候數(shù)據(jù)進(jìn)行了對(duì)比研究，綜合了白堊紀(jì)海相和陸相沉積記錄的古氣候數(shù)據(jù)，大大促進(jìn)我們對(duì)白堊紀(jì)溫室氣候變化的理解，并可能對(duì)應(yīng)對(duì)現(xiàn)今全球變暖的挑戰(zhàn)提供幫助。

關(guān)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(yīng)；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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