气候变化领域集成服务门户(CCPortal): Foraminiferal assemblages; extinctions and appearances associated with the Early Toarcian Oceanic Anoxic Event in the Llanbedr (Mochras Farm) Borehole; Cardigan Bay Basin; United Kingdom

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DOI	10.1016/j.palaeo.2019.109277
	Foraminiferal assemblages; extinctions and appearances associated with the Early Toarcian Oceanic Anoxic Event in the Llanbedr (Mochras Farm) Borehole; Cardigan Bay Basin; United Kingdom
	Reolid M.; Copestake P.; Johnson B.
发表日期	2019
ISSN	0031-0182
卷号	532
英文摘要	The uppermost Pliensbachian-Lower Toarcian sediments recovered from Llanbedr (Mochras Farm) Borehole (North Wales, UK) were deposited in the Cardigan Bay Basin and mainly consist of alternating marls and marly limestones. The current study analyses the foraminiferal assemblages from the cored interval (143 m) that has been assigned to the Spinatum Zone (Upper Pliensbachian) to the lower part of the Bifrons Zone (Middle Toarcian). The foraminiferal assemblages are dominated by the suborders Lagenina and Robertinina. Four main ecostratigraphic intervals have been identified, based on changes in the foraminiferal assemblages that occurred before, during and after the Toarcian Oceanic Anoxic Event (T-OAE). Ecostratigraphic interval I (upper part of the Spinatum Zone) is characterized by a diverse assemblage with specialist, opportunist and intermediate forms. This assemblage is interpreted to represent a phase that pre-dates the biotic crisis. The ecostratigraphic interval II (Tenuicostatum Zone) shows an abrupt increase in opportunist forms such as the genus Reinholdella, and a facultative opportunist such as Paralingulina tenera, which was tolerant to oxygen depleted conditions. This second interval represents the initial biotic crisis phase, in response to decreasing oxygenation. The ecostratigraphic interval III is considered the peak of the biotic crisis, coincident with the negative carbon isotopic excursion (at the base of the Serpentinum Zone) and characterized by the dominance of the opportunist Reinholdella (87–97% of the assemblage) and low diversity. The ecostratigraphic interval IV (upper part of Serpentinum Zone and lower part of Bifrons Zone) is characterized by an increase of diversity and an abrupt decrease in Reinholdella. This assemblage is interpreted to reflect the increased availability of oxygen from deep-infaunal to epifaunal microhabitats and the return to normal conditions at the sea bottom. Ecostratigraphic fluctuations in the Mochras foraminiferal assemblages across the T-OAE event are comparable with those from other parts of the UK, the Lusitanian Basin (Portugal), the Umbria Marche Basin (Italy) and the Atlassic Basin (North Africa). In addition, a foraminiferal turnover is evident across the Pliensbachian-Toarcian boundary and the T-OAE, and reflects the effects of the Early Jurassic biotic crisis on benthic foraminifera. Controlling factors of the biotic crisis are discussed, regarding that anoxic conditions do not necessarily have a lethal effect on all foraminiferal species and other oceanographic and environmental factors need consideration (fragmentation of epicontinental platforms, sea-level changes, crisis of carbonate productivity and temperature changes). © 2019 Elsevier B.V.
英文关键词	Benthic Foraminifera; Biotic crisis; Laurasian Seaway; Lower Toarcian; Opportunists; Upper Pliensbachian
语种	英语
scopus关键词	anoxic conditions; benthic foraminifera; biostratigraphy; environmental factor; extinction; fossil assemblage; Jurassic; limestone; microhabitat; Pliensbachian; Toarcian; Atlantic Ocean; Cardigan Bay; Italy; Lisboa [Portugal]; Lusitanian Basin; North Africa; North Wales; Portugal; Portugal; Umbria-Marche Basin; United Kingdom; United Kingdom; Wales; Foraminifera; Lagenina; Robertinina
来源期刊	Palaeogeography, Palaeoclimatology, Palaeoecology
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/150843
作者单位	Departamento de Geología and CEACT, Universidad de Jaén, Jaén, 23071, Spain; Merlin Energy Resources Ltd., Newberry House, New Street, Ledbury, HR8 2EJ, United Kingdom; 299 North Deeside Road, Cults, Aberdeen, Scotland AB15 9PA, United Kingdom
推荐引用方式 GB/T 7714	Reolid M.,Copestake P.,Johnson B.. Foraminiferal assemblages; extinctions and appearances associated with the Early Toarcian Oceanic Anoxic Event in the Llanbedr (Mochras Farm) Borehole; Cardigan Bay Basin; United Kingdom[J],2019,532.
APA	Reolid M.,Copestake P.,&Johnson B..(2019).Foraminiferal assemblages; extinctions and appearances associated with the Early Toarcian Oceanic Anoxic Event in the Llanbedr (Mochras Farm) Borehole; Cardigan Bay Basin; United Kingdom.Palaeogeography, Palaeoclimatology, Palaeoecology,532.
MLA	Reolid M.,et al."Foraminiferal assemblages; extinctions and appearances associated with the Early Toarcian Oceanic Anoxic Event in the Llanbedr (Mochras Farm) Borehole; Cardigan Bay Basin; United Kingdom".Palaeogeography, Palaeoclimatology, Palaeoecology 532(2019).