Dynamic climate-driven controls on the deposition of the Kimmeridge Clay Formation in the Cleveland Basin, Yorkshire, UK
Authors: Atar Elizabeth , März Christian , Aplin Andrew C. , Dellwig Olaf , Herringshaw Liam G. , Lamoureux-Var Violaine , Leng Melanie J. , Schnetger Bernhard , Wagner Thomas 
Published: August 2019

Abstract. The Kimmeridge Clay Formation (KCF) is a laterally extensive, total-organic-carbon-rich succession deposited throughout northwest Europe during the
Kimmeridgian–Tithonian (Late Jurassic). It has recently been postulated
that an expanded Hadley cell, with an intensified but alternating
hydrological cycle, heavily influenced sedimentation and total organic
carbon (TOC) enrichment by promoting primary productivity and
organic matter burial in the UK sectors of the Boreal Seaway. Consistent
with such climate boundary conditions, petrographic observations, total
organic carbon and carbonate contents, and major and trace element data
presented here indicate that the KCF of the Cleveland Basin was deposited in the Laurasian Seaway under the influence of these conditions. Depositional conditions alternated between three states that produced a
distinct cyclicity in the lithological and geochemical records: lower-variability mudstone intervals (LVMIs) which comprise clay-rich mudstone
and higher-variability mudstone intervals (HVMIs) which comprise TOC-rich
sedimentation and carbonate-rich sedimentation. The lower-variability
mudstone intervals dominate the studied interval but are punctuated by three ∼ 2–4 m thick intervals of alternating TOC-rich and
carbonate-rich sedimentation (HVMIs). During the lower-variability mudstone
intervals, conditions were quiescent with oxic to suboxic bottom water
conditions. During the higher-variability mudstone intervals, highly dynamic conditions resulted in repeated switching of the redox system in a way similar to the modern deep basins of the Baltic Sea. During carbonate-rich sedimentation, oxic conditions prevailed, most likely due to elevated
depositional energies at the seafloor by current–wave action. During
TOC-rich sedimentation, intermittent anoxic–euxinic conditions led to an
enrichment of redox-sensitive and sulfide-forming trace metals at the seafloor
and a preservation of organic matter, and an active Mn–Fe particulate
shuttle delivered redox-sensitive and sulfide-forming trace metals to the
seafloor. In addition, based on TOC–S–Fe relationships, organic matter
sulfurization appears to have increased organic material preservation in
about half of the analysed samples throughout the core, while the remaining
samples were either dominated by excess Fe input into the system or
experienced pyrite oxidation and sulfur loss during oxygenation events. New
Hg∕TOC data do not provide evidence of increased volcanism during this time,
consistent with previous work. Set in the context of recent climate
modelling, our study provides a comprehensive example of the dynamic
climate-driven depositional and redox conditions that can control TOC and
metal accumulations in a shallow epicontinental sea, and it is therefore key to
understanding the formation of similar deposits throughout Earth's history.