10.6084/m9.figshare.3454223.v1
Graham P. Weedon
Graham P.
Weedon
Angela L. Coe
Angela L.
Coe
Ramues W. Gallois
Ramues W.
Gallois
Cyclostratigraphy, orbital tuning and inferred productivity for the type Kimmeridge Clay (Late Jurassic), Southern England
Geological Society of London
2016
siliciclastic mineral dilution
type Kimmeridge Clay Fm
type Kimmeridge Clay
Kimmeridge Clay Fm
productivity
carbon content
Geology
2016-06-21 11:59:04
Dataset
https://geolsoc.figshare.com/articles/dataset/Cyclostratigraphy_orbital_tuning_and_inferred_productivity_for_the_type_Kimmeridge_Clay_Late_Jurassic_Southern_England/3454223
<p>Three independently measured variables (magnetic susceptibility, photoelectric factor and total gamma-ray) obtained from throughout
the type Kimmeridge Clay Fm in Dorset (Southern England) were used to identify regular metre-scale, sedimentary cycles. Spectral
analysis demonstrates that for long stratigraphical intervals the cycles are expressed as large-amplitude cycles of 1.87–4.05
m wavelength and smaller-amplitude cycles of around half that wavelength. These cycles are interpreted to record orbital obliquity
and precession, respectively. The much larger amplitude of the inferred obliquity cycles compared with the precession cycles
may indicate a high-latitude climatic forcing transferred to lower latitudes via sea-level variations. Orbital tuning indicates
that the Early Kimmeridgian (<em>sensu anglico</em>) lasted at least 3.6 Ma (95 longer-wavelength cycles) and the Late Kimmeridgian at least 3.9 Ma (103 longer-wavelength cycles).
The first detailed productivity estimates for the Kimmeridge Clay Fm, on a cycle-by-cycle calculation, indicate that average
productivity of the type Kimmeridge Clay (220 g m<sup>−2</sup> a<sup>−1</sup>) was less than the average productivity on modern continental shelves. The high average organic carbon content of the type
Kimmeridge Clay (3.8% total organic carbon) cannot be attributed to high average productivity. However, the average organic
carbon content is consistent with low siliciclastic mineral dilution of organic matter and/or elevated preservation linked
to reduced bottom-water oxygenation.
</p>