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| Titel |
Boreal organic-rich sediments of Oceanic Anoxic Event 2: dinoflagellate cysts, anoxia and an intensified hydrological cycle |
| VerfasserIn |
Tom Young, Ian Jarvis, Paul Dodsworth, João Trabucho-Alexandre, Bruce Tocher, Martyn Waller |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250092436
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| Publikation (Nr.) |
 EGU/EGU2014-6781.pdf |
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| Zusammenfassung |
| Diverse palynological assemblages have been recovered from Cenomanian-Turonian
boundary (CTB) successions in the central North Sea and onshore NE England that contain
organic-rich deposits characteristic of Oceanic Anoxic Event 2 (OAE2). The stratigraphic
extent of the event is evidenced by a marked positive excursion in δ13Corg profiles.
Palynomorphs are absent in the chalks immediately underlying the onset of the positive
isotope excursion. Pulses of abundant spores and pollen are associated with the appearance of
organic-walled dinoflagellate cysts (dinocysts) in marlier but organic-lean sediments
characterizing the early stages of the event. Dinocyst assemblages are indicative of
an outer neritic environment, with high abundances of Spiniferites spp. and the
presence species such as Pterodinium cornutum. Black shales are confined to the
later stages of the CTB interval and the peak of the δ13Corg excursion. These are
characterized by abundant Cyclonephelium, which has been reported to be representative
of anoxic conditions, but also reduced salinity and lower nutrient environments.
Changes of the assemblage from open water species to that of species associated
with lower salinity/shallower water environments is coeval with a trend to more
negative δ18O values, indicative of increasing water temperature. It is postulated that
intensification the hydrological cycle during latest Cenomanian global warming and
eustatic sea-level rise, increased the flow of freshwater into the oceans and modified
ocean circulation patterns, transporting shallower water species out into open water. |
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