摘要:
白垩纪大洋红层代表典型的深水富氧沉积环境,笔者从现代海洋铁盐投放实验入手,探讨了大洋红层的产生机制,论述了铁元素在白垩纪大洋富氧环境发生过程中的作用。白垩纪剧烈的岩浆活动在海底产生大量的富含铁元素的基性和超基性岩石,在与海水发生反应时,岩石中的铁元素进入海水中。海水中的铁元素是海洋浮游植物宝贵的营养盐类,其含量的增加可激发浮游植物的爆发性繁盛,而这一生命过程可以吸收海水中大量的CO2,并且产生巨量的O2。伴随海水中溶解O2浓度的不断升高,以富含Fe3+的红色沉积物为特征的海洋富氧环境出现。中、晚白垩世大洋红层的产生是一个与火山活动密切相关、同时又涉及沉积学及生物—海洋地球化学作用的复杂过程。
Abstract:
The occurrence of Cretaceous Oceanic Red Beds (CORBs) suggest an oxic ocean in Late Cretaceous. Based on the data from the modern ocean iron release experiment, we discussed in this paper the function of iron in the oceanic oxic proces and the mechanism of oceanic environment change from anoxic to oxic in Cretaceous. Submarine volcanism provides enomous basic and ultrabasic lava, which contains a certain amount of Fe, onto the seafloor. When the lava react with seawater, the element Fe will be released to and dissolve in seawater. Iron is a micronutrient essentially required by the synthesis of enzymes during photosynthesis in the oceanic environment, and will help phytoplankton boom rapidly. The booming of phytoplankton needs carbon dioxide and will take it from the nature, wherever it is in atmosphere or in ocean. This process will produce a great amount of oxygen, and cause the formation of an oxic environment characterized by red sediment rich in Fe3+. The forming mechanism of the CORBs is supposed to be a complicated bio-oceanic-geochemical process related to submarine magmatic activities.
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