气候变化领域集成服务门户(CCPortal): Cretaceous oceanic anoxic events prolonged by phosphorus cycle feedbacks

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DOI	10.5194/cp-16-757-2020
	Cretaceous oceanic anoxic events prolonged by phosphorus cycle feedbacks
	Beil S.; Kuhnt W.; Holbourn A.; Scholz F.; Oxmann J.; Wallmann K.; Lorenzen J.; Aquit M.; Hassane Chellai E.
发表日期	2020
ISSN	18149324
起始页码	757
结束页码	782
卷号	16 期号:2
英文摘要	Oceanic anoxic events (OAEs) document major perturbations of the global carbon cycle with repercussions for the Earths climate and ocean circulation that are relevant to understanding future climate trends. Here, we compare the onset and development of Cretaceous OAE1a and OAE2 in two drill cores with unusually high sedimentation rates from the Vocontian Basin (southern France) and Tarfaya Basin (southern Morocco). OAE1a and OAE2 exhibit remarkable similarities in the evolution of their carbon isotope (δ 13C) records, with long-lasting negative excursions preceding the onset of the main positive excursions, supporting the view that both OAEs were triggered by massive emissions of volcanic CO2 into the atmosphere. However, there are substantial differences, notably in the durations of individual phases within the δ 13C positive excursions of both OAEs. Based on analysis of cyclic sediment variations, we estimate the duration of individual phases within OAE1a and OAE2. We identify (1) a precursor phase (negative excursion) lasting ∼ 430 kyr for OAE1a and ∼ 130 kyr for OAE2, (2) an onset phase of ∼ 390 and ∼ 70 kyr, (3) a peak phase of ∼ 600 and ∼ 90 kyr, (4) a plateau phase of ∼ 1340 and ∼ 200 kyr, and (5) a recovery phase of ∼ 380 and ∼ 440 kyr. The total duration of the positive ∼ 13C excursion is estimated at 2700 kyr for OAE1a and 790 kyr for OAE2, and that of the main carbon accumulation phase is estimated at 980 and 180 kyr. The long-lasting peak, plateau and recovery phases imply fundamental changes in global nutrient cycles either (1) by submarine basalt-seawater interactions, (2) through excess nutrient inputs to the oceans by increasing continental weathering and river discharge, or (3) through nutrient recycling from the marine sediment reservoir. We investigated the role of phosphorus in the development of carbon accumulation by analysing phosphorus speciation across OAE2 and the mid-Cenomanian Event (MCE) in the Tarfaya Basin. The ratios of organic carbon and total nitrogen to reactive phosphorus (Corg=Preact and Ntotal=Preact) prior to OAE2 and the MCE hover close to or below the Redfield ratio characteristic of marine organic matter. Decreases in reactive phosphorus resulting in Corg=Preact and Ntotal=Preact above the Redfield ratio during the later phase of OAE2 and the MCE indicate leakage from the sedimentary column into the water column under the influence of intensified and expanded oxygen minimum zones. These results suggest that a positive feedback loop, rooted in the benthic phosphorus cycle, contributed to increased marine productivity and carbon burial over an extended period of time during OAEs. © Author(s) 2020. This work is distributed under the Creative Commons Attribution 4.0 License.
语种	英语
scopus关键词	anoxic conditions; carbon cycle; carbon isotope; climate feedback; Cretaceous; leakage; marine sediment; oxygen minimum layer; paleoclimate; phosphorus cycle; sequence stratigraphy; water column; France; Laayoune-Sakia al Hamra; Morocco; Tarfaya Basin; Vocontian Trough
来源期刊	Climate of the Past
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/146719
作者单位	Institute of Geosciences, Kiel University, Ludewig-Meyn-Str. 10-14, Kiel, 24118, Germany; GEOMAR Helmholtz Centre for Ocean Research Kiel, Wischhofstr. 1-3, Kiel, 24148, Germany; OCP S.A., Direction de Recherche et Développement, Recherche Géologique, Youssoufia, 46300, Morocco; Department of Geology, Faculty of Sciences Semlalia, Cadi Ayyad University, Marrakesh, Morocco
推荐引用方式 GB/T 7714	Beil S.,Kuhnt W.,Holbourn A.,et al. Cretaceous oceanic anoxic events prolonged by phosphorus cycle feedbacks[J],2020,16(2).
APA	Beil S..,Kuhnt W..,Holbourn A..,Scholz F..,Oxmann J..,...&Hassane Chellai E..(2020).Cretaceous oceanic anoxic events prolonged by phosphorus cycle feedbacks.Climate of the Past,16(2).
MLA	Beil S.,et al."Cretaceous oceanic anoxic events prolonged by phosphorus cycle feedbacks".Climate of the Past 16.2(2020).