Late Ryazanian black shales in the Southern North Sea Basin and their lithostratigraphical significance

Lott, G.K.; Thomas, Joanna E.; Riding, James B.; Davey, Roger J.; Butler, N.

doi:10.1144/pygs.47.4.321

Cited by 10 publications

(4 citation statements)

References 6 publications

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“…Late Ryazanian assemblages are characterised by a decrease in the abundance and diversity of dinoflagellate cysts in the DSK2 Zone and younger strata. Lott et al (1989) also noted this phenomenon and related the differences to a latest Ryazanian transgression. It is believed, therefore, that the dinoflagellate cyst diversity and abundance fluctuations correspond well to both the sealevel changes at the Jurassic-Cretaceous boundary proposed by Haq et al (1987), and to the model of Rawson & Riley (1982).…”

Section: Biozonation Palaeotemperature and Sea-level Changesmentioning

confidence: 82%

The Jurassic dinoflagellate cyst zonation of Subboreal Northwest Europe

Poulsen

Riding

2003

GEUS Bulletin

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With an appendix by Bjørn Buchardt: Oxygen isotope palaeotemperatures from the Jurassic in Northwest EuropeThe Jurassic dinoflagellate cyst zonation for the British-Danish area is revised and discussed in relation to palaeoenvironmental factors, in particular, eustatic changes and fluctuations in palaeotemperature. The stepwise evolution of dinoflagellate cyst assemblages as defined by inceptions and apparent extinctions was largely controlled by sea-level change, particularly during intervals with significant short-term eustatic fluctuations. During times characterised by less pronounced, or longer term, sea-level change, fluctuations in oceanic palaeotemperatures appear to have influenced dinoflagellate evolution. Differences in the ranges of certain taxa between Denmark and the United Kingdom may be partly related to differences in palaeotemperature.

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Section: Biozonation Palaeotemperature and Sea-level Changesmentioning

confidence: 82%

The Jurassic dinoflagellate cyst zonation of Subboreal Northwest Europe

Poulsen

Riding

2003

GEUS Bulletin

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“…Although the deposition of this type of sediments ended during the Portlandian in most areas, Ž . Lott et al 1989 suggest that the organic-rich shale deposition may have continued into the upper Ryaza-Ž . nian stenomphalus Zone in the deeper parts of the then existing basins.…”

Section: The Late Kimmeridgian-portlandian Arid Phasementioning

confidence: 99%

Late Jurassic to earliest Cretaceous palaeoclimatic evolution of the southern North Sea

Abbink

Targarona

Brinkhuis

et al. 2001

Global and Planetary Change

222

151

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“…One such minor transgressive event is recorded, for example, by the quasi-marine Cinder Bed which records a base Kochi Chronozone (Early Ryazanian) marine incursion into the largely non-marine Wessex Basin (Rawson & Riley 1982). An Early Ryazanian transgressive trend is also reflected in the regional onlap of Ryazanian 'hot shales' onto the flanks of the Central Graben in the UK sector (Gatliff et al 1994), culminating in the deposition of Upper Ryazanian black laminated mudstones on Kimmeridgian strata in eastern England (Lott et al 1986(Lott et al , 1989.…”

Section: Role Of Sea-level Variationmentioning

confidence: 99%

Volgian–Ryazanian ‘hot shales’ of the Bo Member (Farsund Formation) in the Danish Central Graben, North Sea: stratigraphy, facies and geochemistry

et al. 2003

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Upper Jurassic – lowermost Cretaceous marine mudstones represent the most significant source of hydrocarbons in the Central and Northern North Sea. Of particular importance in the Danish sector of the Central Graben is a succession of radioactive ‘hot shales’ referred to the Bo Member, in the upper levels of the Farsund Formation (Kimmeridge Clay Formation equivalent). This mudstone-dominated succession is typically 15–30 m thick and has a total organic carbon (TOC) content of 3–8%, though locally exceeding 15%. Although truncated on some structural highs, the Bo Member is a persistent feature of the Danish Central Graben. Lateral variation in both thickness and organic richness is attributed to intrabasinal structural topography and to the location of sediment input centres. Detailed study of the dinoflagellate cyst biostratigraphy of 10 wells indicates that the onset of enhanced organic carbon burial began in the middle–late Middle Volgian in this portion of the Central Graben. The Bo Member, representing the peak of organic carbon enrichment, is largely of Early Ryazanian age. Core data (Jeppe-1, E-1 wells) indicate that the organic-rich shales of the Bo Member are not wholly of hemipelagic origin, as commonly assumed, but may locally be dominated by fine-grained turbidites. Absence of bioturbation, well-preserved lamination and high TOC values suggest that bottom waters were predominantly anoxic although the presence of in-situ benthic bivalves at discrete horizons in the E-1 well suggests that suboxic conditions prevailed on occasion. The Bo Member is a good to very good source rock, showing very high pyrolysis yields (10–100 kg HC/ton rock) and Hydrogen Index (HI) values in the range 200–600. In particular, the Bo Member is characterised by an abundance of 28,30 bisnorhopane (H28), a compound that is indicative of anoxic environments. These new data from the Danish sector of the Central Graben are compatible with the model of Tyson et al. (1979) in which the accumulation of organic-rich mudstones was controlled primarily by bottom-water anoxia beneath a stratified watermass. A number of factors probably contributed to the development of watermass stratification, both intrinsic such as the tectonic morphology of the graben system and extrinsic including climate and sea-level stand.

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Late Ryazanian black shales in the Southern North Sea Basin and their lithostratigraphical significance

Cited by 10 publications

References 6 publications

The Jurassic dinoflagellate cyst zonation of Subboreal Northwest Europe

The Jurassic dinoflagellate cyst zonation of Subboreal Northwest Europe

Late Jurassic to earliest Cretaceous palaeoclimatic evolution of the southern North Sea

Volgian–Ryazanian ‘hot shales’ of the Bo Member (Farsund Formation) in the Danish Central Graben, North Sea: stratigraphy, facies and geochemistry

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