Erbacher J, Huber B T, Norris R D, Markey M
Bundesanstalt für Geowissenschaften und Rohstoffe, Referat Meeresgeologie, Hannover, Germany.
Nature. 2001 Jan 18;409(6818):325-7. doi: 10.1038/35053041.
Ocean anoxic events were periods of high carbon burial that led to drawdown of atmospheric carbon dioxide, lowering of bottom-water oxygen concentrations and, in many cases, significant biological extinction. Most ocean anoxic events are thought to be caused by high productivity and export of carbon from surface waters which is then preserved in organic-rich sediments, known as black shales. But the factors that triggered some of these events remain uncertain. Here we present stable isotope data from a mid-Cretaceous ocean anoxic event that occurred 112 Myr ago, and that point to increased thermohaline stratification as the probable cause. Ocean anoxic event 1b is associated with an increase in surface-water temperatures and runoff that led to decreased bottom-water formation and elevated carbon burial in the restricted basins of the western Tethys and North Atlantic. This event is in many ways similar to that which led to the more recent Plio-Pleistocene Mediterranean sapropels, but the greater geographical extent and longer duration (approximately 46 kyr) of ocean anoxic event 1b suggest that processes leading to such ocean anoxic events in the North Atlantic and western Tethys were able to act over a much larger region, and sequester far more carbon, than any of the Quaternary sapropels.
海洋缺氧事件是高碳埋藏时期，导致大气二氧化碳减少、底层水氧浓度降低，且在许多情况下造成重大生物灭绝。大多数海洋缺氧事件被认为是由表层水高生产力和碳输出引起的，这些碳随后保存在富含有机质的沉积物（即黑色页岩）中。但引发其中一些事件的因素仍不确定。在此，我们展示了来自1.12亿年前白垩纪中期海洋缺氧事件的稳定同位素数据，这些数据表明热盐分层加剧可能是其原因。海洋缺氧事件1b与表层水温升高和径流增加有关，这导致底层水形成减少，以及在西特提斯海和北大西洋的受限盆地中碳埋藏增加。该事件在许多方面与导致更近的上新世-更新世地中海腐泥层的事件相似，但海洋缺氧事件1b更大的地理范围和更长的持续时间（约4.6万年）表明，导致北大西洋和西特提斯海此类海洋缺氧事件的过程，能够在比任何第四纪腐泥层大得多的区域起作用，并封存更多的碳。
