摘要
白垩纪中期(约125～88Ma)海相富有机碳沉积广泛发育于全球各主要洋盆和沉降区,是许多大油田的重要烃源岩。文中从地球生物学的角度探讨了当时海相富有机碳沉积的地质背景和主控因素,认为在白垩纪中期全球事件频发的特殊背景下,保存条件(大洋缺氧)和生产力的提高共同控制了有机质的富集。大洋缺氧不但加快了海洋生物的灭绝和更替,使有机质大量堆积,而且促进了营养元素(P、N、Fe等)的再生和厌氧自养型海洋微生物(如蓝细菌、绿硫细菌和古菌类等)的极度繁盛,提高了生产力水平;而高的生产力又反过来加剧了海洋的缺氧。新的研究成果(Os同位素证据)表明,白垩纪大规模海底火山作用引发了持续的温室效应和海水循环的静滞、紊乱以及弱上升流发育,进而导致生产力的提高和大洋缺氧事件(OAE)的发生,最终造成有机质的广泛堆积和保存。
The mid-Cretaceous（～125-88 Ma） is characterized by a remarkable increase of global organic matter（OM） accumulations-the significant source rock of many large oil fields in most oceanic basins.Based on the previous discussion about geological setting and major controlling factors on the marine organic carbon-rich accumulation,this paper proposes that both high primary productivity（PP） and oceanic anoxic events（OAE） controlled the wide distribution of marine organic carbon-rich sediments in the mid-Cretaceous.In fact,OAE not only sped up the extinction and the replacement of marine life,causing huge amounts of OM accumulation,but also promoted the regeneration of nutrients（e.g.P,N,Fe） and the flourish of anaerobic autotrophic micro-organisms（e.g.green sulfur bacteria,cyanobacteria,archaea） as well.The high PP in turn exacerbated the oceanic anoxia.During that period,the Cretaceous large igneous events triggered the sustaining greenhouse climate and abnormal oceanic environments together with euxinic conditions,confusion currents and weak upwelling,which led to the improved productivity and OAE,and eventually,caused the extensive accumulation of organic matter.
出处
《地学前缘》
EI
CAS
CSCD
北大核心
2009年第5期143-152,共10页
Earth Science Frontiers
基金
国家基础研究发展计划"973"项目(2006CB701403)
国家自然科学基金项目(40872016
40672020)
中国石油化工股份有限公司资助项目(G0800-06-ZS-319)
关键词
海相富有机碳沉积
大洋缺氧事件
古海洋生产力
白垩纪中期
marine organic carbon-rich sediments
Oceanic Anoxic Events（OAEs）
paleo-oceanic productivity
mid-Cretaceous
