The Late Jurassic – earliest Cretaceous time interval was characterized by a widespread distribution of dysoxiс–anoxiс environments in temperate- and high-latitude epicontinental seas, which could be defined as a shelf dysoxic–anoxic event (SDAE). In contrast to black shales related to oceanic anoxic events, deposits generated by the SDAE were especially common in shelf sites in the Northern Hemisphere. The onset and termination of the SDAE was strongly diachronous across different regions. The SDAE was not associated with significant disturbances of the carbon cycle. Deposition of organic-carbon-rich sediment and the existence of dysoxic–anoxic conditions during the SDAE lasted up toc.20 Ma, but this event did not cause any remarkable biotic extinction. Temperate- and high-latitude black shale occurrences across the Jurassic–Cretaceous boundary have been reviewed. Two patterns of black shale deposition during the SDAE are recognized: (1) Subboreal type, with numerous thin black shale beds, bounded by sediments with very low total organic carbon (TOC) values; and (2) Boreal type, distinguished by predominantly thick black shale successions showing high TOC values and prolonged anoxic–dysoxic conditions. These types appear to be unrelated to differences in accommodation space, and can be clearly recognized irrespective of the thickness of shale-bearing units. Black shales in high-latitude areas in the Southern Hemisphere strongly resemble Boreal types of black shale by their mode of occurrence. The causes of this SDAE are linked to long-term warming and changes in oceanic circulation. Additionally, the long-term disturbance of planktonic communities may have triggered overall increased productivity in anoxia-prone environments.

中文翻译：

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晚侏罗世——最早的白垩纪陆架长期缺氧-缺氧事件及其可能原因

晚侏罗世-最早的白垩纪时间间隔的特点是在温带和高纬度陆缘海域广泛分布缺氧-缺氧环境，可以将其定义为陆架缺氧-缺氧事件（SDAE）。与与海洋缺氧事件相关的黑色页岩相比，SDAE 产生的沉积物在北半球的陆架地点尤为常见。SDAE 的发生和终止在不同地区具有很强的历时性。SDAE 与碳循环的显着干扰无关。SDAE期间富含有机碳的沉积物的沉积和缺氧-缺氧条件的存在持续了C。20 Ma，但这一事件并没有引起任何显着的生物灭绝。回顾了侏罗纪-白垩纪边界的温带和高纬度黑色页岩矿点。SDAE 期间的黑色页岩沉积有两种模式：（1）亚寒带类型，有许多薄黑色页岩床，以总有机碳（TOC）值非常低的沉积物为界；(2) 北方类型，以厚厚的黑色页岩系列为主，显示出高 TOC 值和长时间的缺氧-缺氧条件。这些类型似乎与容纳空间的差异无关，无论页岩单元的厚度如何，都可以清楚地识别出来。南半球高纬度地区的黑色页岩在产状方面与北方类型的黑色页岩非常相似。这种 SDAE 的原因与长期变暖和海洋环流的变化有关。此外，浮游群落的长期干扰可能引发了缺氧易发环境中生产力的整体提高。