Hadley circulation and precipitation changes control black shale deposition in the Late Jurassic Boreal Seaway

Armstrong, Howard A.; Wagner, Thomas; Herringshaw, Liam G.; Farnsworth, Alexander J.; Lunt, Daniel J.; Harland, M.; Imber, Jonathan; Loptson, Claire; Atar, Elizabeth F.L.

doi:10.1002/2015pa002911

Hadley circulation and precipitation changes control black shale deposition in the Late Jurassic Boreal Seaway

Armstrong, Howard A.; Wagner, Thomas; Herringshaw, Liam G.; Farnsworth, Alexander J.; Lunt, Daniel J.; Harland, M.; Imber, Jonathan; Loptson, Claire; Atar, Elizabeth F.L.

Authors

Howard A. Armstrong

Thomas Wagner

Liam G. Herringshaw

Alexander J. Farnsworth

Daniel J. Lunt

M. Harland

Jonathan Imber

Claire Loptson

Elizabeth F.L. Atar

Abstract

New climate simulations using the HadCM3L model with a paleogeography of the Late Jurassic [155.5 Ma], and proxy-data corroborate that warm and wet tropical-like conditions reached as far north as the UK sector of the Jurassic Boreal Seaway [~35oN]. This is associated with a northern hemisphere Jurassic Hadley cell and an intensified subtropical jet which both extend significantly polewards than in the modern (July-September). Deposition of the Kimmeridge Clay Formation [KCF] occurred in the shallow, storm-dominated, epeiric Boreal Seaway. High resolution paleo-environmental proxy data from the Kimmeridge Clay Formation [KCF; ~155–150 Ma], UK are used to test for the role of tropical atmospheric circulation on meter-scale heterogeneities in black shale deposition. Proxy and model data show that the most organic-rich section [eudoxus to mid-hudlestoni zones] is characterised by a positive δ13Corg excursion and up to 37 wt% total organic carbon [%TOC]. Orbital-modulation of organic carbon burial primarily in the long eccentricity power band combined with a clear positive correlation between %TOC carbonate-free and the kaolinite/illite ratio supports peak organic carbon burial under the influence of very humid climate conditions, similar to the modern tropics. This re-interpretation of large-scale climate relationships, supported by independent modelling and geological data, has profound implications for atmospheric circulation patterns and processes affecting marine productivity and organic carbon burial further north along the Boreal Seaway, including the Arctic.

Citation

Armstrong, H. A., Wagner, T., Herringshaw, L. G., Farnsworth, A. J., Lunt, D. J., Harland, M., …Atar, E. F. (2016). Hadley circulation and precipitation changes control black shale deposition in the Late Jurassic Boreal Seaway. Paleoceanography, 31(8), 1041-1053. https://doi.org/10.1002/2015pa002911

Journal Article Type	Article
Acceptance Date	Jul 5, 2016
Online Publication Date	Aug 3, 2016
Publication Date	Aug 3, 2016
Deposit Date	Jul 28, 2016
Publicly Available Date	Jul 28, 2016
Journal	Paleoceanography
Print ISSN	0883-8305
Electronic ISSN	1944-9186
Publisher	American Geophysical Union
Peer Reviewed	Peer Reviewed
Volume	31
Issue	8
Pages	1041-1053
DOI	https://doi.org/10.1002/2015pa002911

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Copyright Statement
© 2016. The Authors. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.