大洋钻探计划与古海洋学的发展

OCEAN DRILLING PROGRAM AND THE DEVELOPMENT OF PALEOCEANOGRAPHY

介绍了大洋钻探（包括其前身海钻探）计划，阐述了古海洋学在这个计划实施的推动下所获得的巨大进展。大洋钻探促并完善了大洋沉积的高分辨率的浮游生物带的建立，并确定了各个带的绝对年龄，最精细达１０万年或更短；揭示出大洋热结构在地质历史上的变化，如晚白垩世时全球大洋无冰，温度大大高于今日，早渐新世开始形成冰冷的南极底部水，促使大洋的热结构产生相应的变化；也查明了大洋的碳酸盐补偿深度在地质历史时期的变化及各洋盆在同一时期其碳酸盐补偿深度的相异性。海底高有机碳含量沉积的发现、白垩纪中期缺氧事件的认识及深海沉积中大量缺失面的查知无疑是古海洋学研究中的重大进展。２５年以来对大洋进行钻探的研究也部分揭示了古代大洋在表面及三维空间的洋流循环模式。

A brief introduction has been made of Ocean Drilling Program(ODP) based on personal experience of taking part in one of its legs. Paleoceanography,a new branch of geology ,has been develoting greatly since the early 1970' s due to tremendous imtetus gained from the operation of ODP and its predecessor DSDP. Fiue-resolution planktonic zones of oceanic deposits have been established, modified, and correlated to the magnetostratigraphy with individual zones defined as fine as 100 000 years or shorter.Changes in the thermal structure of the ocean have been revealed. For example,the ocean during the Late Cretaceous was ice-free, much warmer than today; the cold Antarctic bottom water formed initially in early Oligocene has resulted in the change of global thermal structure. The carbonate comensation depth(CCD)of the ocean has been fluctuating with time,and was different among individual ocean basins at the same time.It is obviously a great success for paleoceanography to find out widespread deposition of high organic carbon content in the Middle Cretaceous ocean(the understanding of anoxic event),and to recognize numerous hiatuses in the deep-sea sediments.Reconstruction of surface and three-dimensional circulation pattern of the paleocean is mainlya synthetic result of ODP(and DSDP) for 25 years.