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

H.A. Armstrong, Thomas Wagner, L.G. Herringshaw, Alexander Farnsworth, Dan Lunt, M Harland, J Imber, Claire Loptson, E Atar

Research output: Contribution to journalArticle (Academic Journal)peer-review

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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.
Original languageEnglish
Pages (from-to)1041-1053
Number of pages13
JournalPaleoceanography
Volume31
Issue number8
Early online date14 Jul 2016
DOIs
Publication statusPublished - Aug 2016

Keywords

  • Paleoclimatology and paleoceanography
  • anoxic and hypoxic environments
  • regional climate change
  • paleoclimatology
  • Jurassic

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