白垩纪早中期(Valanginian晚期-Turonian早期)增温过程及陆地生物响应

THE GLOBAL WARMING PROCESS AND TERRESTRIAL BIOTA RESPONSE DURING EARLY TO MIDDLE CRETACEOUS PERIOD(LATE VALANGINIAN-EARLY TURONIAN)

白垩纪气候总体经历了增温、高温和降温3个阶段,其中白垩纪早中期(Valanginian晚期-Turonian早期,约135~92 Ma)经历了持续和长时间的增温过程。伴随着增温,陆地生物和生态系统经历了快速的辐射和演化。虽然学术界对白垩纪中期的温室气候状态已有深入研究,但对早中期的升温过程及陆地生物响应,仍缺乏深入了解。本研究基于全球已有温度和陆相化石记录,对白垩纪早中期的增温过程及陆地生物响应进行了初步梳理。白垩纪古温度证据显示,早白垩世Valanginian晚期至Barremian期,全球温度逐渐升高,在Aptian最早期(约120 Ma)迎来第一个峰值,最高表层海水温度可达32℃以上,Aptian中-晚期,则经历了一次温度的下降,自Albian期开始又不断升高,在Cenomanian晚期-Turonian早期达到最高,最高表层海水温度可达37℃以上。伴随着温度逐渐升高,以被子植物和鸟类等为代表的陆地生物快速辐射,从中生代陆地生态系统向现代陆地生态系统转变。全球白垩纪早中期陆地生物群的发展和分布与温度的逐渐增高可能存在密切关系。早白垩世中晚期(Barremian-Aptian早期),伴随着温度的逐渐增高,全球陆地生物的演化迎来了一次大辐射。中国东北地区白垩纪早中期发育了热河生物群、阜新生物群(延吉生物群)和松花江生物群(早期),这些生物群的辐射和演化与温度等气候的变化具有密切关系。

The Cretaceous is a typical greenhouse world.The climate of the Cretaceous Period can be divided into three periods:warming,hot,and cooling.Among them,a long global warming process occurred during the Early to Middle Cretaceous(late Valanginian to early Turonian,135~92 Ma).Simultaneous with global warming,terrestrial organisms and ecosystems underwent rapid evolution and radiation.However,the warming process during the Early to Middle Cretaceous,especially the temperature records of the non-marine Cretaceous and the response of terrestrial biota,is still not well understood.Based on a summary of marine and non-marine temperature records,as well as terrestrial fossil records,the global warming process and the response of terrestrial biology during the Early to Middle Cretaceous period were investigated in this study.The published marine Cretaceous temperature data indicate that global temperatures gradually increased from the late Valanginian to the Barremian Stages,reaching the peak during earliest Aptian,with SST of>32℃;and then,there was a decline of temperature during the middle and late Aptian stage,followed by further increase since Albian,reaching the maximum during the late Cenomanian-early Turonian stage,with SST of>37℃.The temperature records of the non-marine Cretaceous imply a lower temperature during the late Valanginian to early Barremian,followed by a gradual increase from the Aptian to the Turonian.Terrestrial biota was widely distributed during the Valanginian to early Albian but decreased during the late Albian to Turonian as the global sea level increased.NE China developed well-preserved terrestrial biota during the Early to Middle Cretaceous,including the Jehol Biota,Fuxin Biota(Yanji Biota),and Songhuajiang Biota.The distribution and development of global terrestrial biota are closely related to the progress of warming during the Early to Middle Cretaceous Period.With a gradual increase in temperature,terrestrial biota,such as angiosperms and birds,radiated rapidly.Modern terrestrial ecosystems formed gradually during this period,evolving from Mesozoic to modern ecosystems.Our study indicates that the increase in temperature played an important role in the radiation evolution of the early to mid-stage Jehol Biota during the late Valanginian to Barremian.