 |
| Titel |
Long-term selective degradation of organic-walled dinoflagellate cysts in a Maderia Abyssal Plain turbidite |
| VerfasserIn |
Daniel D. Gray, Gerard J. M. Versteegh, Karin A. F. Zonneveld |
| Konferenz |
EGU General Assembly 2017
|
| Medientyp |
Artikel
|
| Sprache |
en
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250142801
|
| Publikation (Nr.) |
 EGU/EGU2017-6462.pdf |
|
|
|
|
|
| Zusammenfassung |
| Post-depositional sedimentary dinoflagellate cyst degradation is well documented under oxic conditions, a process characterised by the preferential loss of “S-cysts” at elevated ambient oxygen concentrations. Establishing a quantitative relationship between degradation rates and aerobic exposure would allow paleo-bottom oxygen water profiles to be reconstructed. Here we trace the long-term (centennial-millennial scale) degradation pattern of a dinocyst assemblage from the F-turbidite of core GeoB20305-7 retrieved at Maderia Abyssal Plain (MAP), with reference to a suite of inorganic and organic geochemical profiles. A downward-migrating oxidation front advances through the the upper part of the depositional unit, resulting in a near-total loss of the Peridiniales cyst fraction dominated by Brigantedinium spp. and Echinidinium spp. specimens. In contrast, Gonyaulacales species have subdued degradation responses resulting in the progressive reconstitution of the cyst assemblage away from its source signal. Assuming a diffusion-dominated migration of the oxidation front and a basic parameterisation of boundary conditions we estimate the oxygen exposure time (OET) of the oxidised section to be ~5000 years. The resulting degradation profile is well-fitted by an exponential decay curve. Implications of these observations are discussed with regard to existing schemes for dinoflagellate based proxy interpretation in oxic environments. |
|
|
|
|
|
|