摘要
DSDP 524区中生代最晚期和第三纪最早期的沉积物中,保存着白垩纪末期环境变化和生物演化的详细纪录。我们对该孔进行了加密取样,样品间距大致相当于100年或1000年的时间间隔,同时对样品进行了碳酸盐含量、微量元素成分及碳氧同位素分析。我们所得到的数据可以解释为白垩纪末期生物大批死亡的结果,当时大量远洋地区的生物扫地以尽。养料锐减导致部分从河流带来的溶解CO_2转移到大气圈,致使在长达40,000年的时间内,空气中的CO_2剧增。由此产生的温室效应就是氧同位素所揭示的温度升高的原因。 第三纪最早期沉积物中,包括来自“白垩纪生物群”中的化石,有的已经过再沉积作用,有的则是这场灾难的最后幸存者。我们的资料表明,大量远洋生物的灭绝是在第三纪最早期的不利环境中发生的。而这种异常的环境则是生物大批死亡的结果,且持续有几千年之久。恐龙就是因为温度灾难性升高产生的热异常而灭绝的。 大洋中生物大批灭绝的原因,与巨大的天外星体的陨落有关,界线附近的铱异常即其标志,我们的资料与许靖华不久前发表的彗星冲击说是不抵触的。
The latest Mesozoic and earliest Tertiary sediments at DSDP Site 524 provided an amplified record of environmental and evolutionary changes at the end of Cretaceous. Closely spaced samples, representing time intervals down to the order of 102 or 103 years, were analysed for their bulk carbonate and trace-metal compositions, and for oxygen & carbon isotopic compositions. Our results are interpreted as a consequence of the mass-mortailty at the end of Cretaceous when much of the biomass in the pelagic realm of the ocean waters was wiped out. The reduction of fertility led to a partial transfer of dissolved CO2 from river-input to the atmosphere, resulting in a large increase of the CO2 tin the air during 40,000 years. The green-house effect of the increased CO2 is believed to be the cause of temperature rise revealed by the oxygen-isotope data.The earliest Tertiary sediments include fossils from the'Cretaceous taxa', which may include both reworked individuals and last survivors of the catastrophe. Our data suggest that the extinction of many of the pelagic organisms took place during the ear Hest Tert tiary in a stressed environment consequent upon the mass mortality and over a pericd of a few tens of thuosands years. The dinosaurs became extinct because of thermal stress associated with the catastrophic rise of temperature.The cause of mass mortality in the oceans is linked to the fall of a arge extra-terrestrial object, as suggested by an iridium anolmaly at the boundary. Our data do not contradict the scenario of cometary impact cs suggested by the first author in a previous publication.
出处
《吉林大学学报（地球科学版）》
EI
CAS
1982年第1期1-14,共14页
Journal of Jilin University：Earth Science Edition
