Orbital chronology for the Cenomanian-Turonian Oceanic Anoxic Event 2 and its environmental implications
Final Report Abstract
The Cenomanian–Turonian OAE 2 is reflected by one of the most extreme carbon cycle perturbations in Earth’s history possibly triggered by massive volcanic CO2 degassing during the emplacement of large igneous provinces (LIPs). Severe climatic, oceanographic and biotic feedbacks are reported from different depositional settings. The nature of these changes as well as their spatial and temporal dimension is still not well understood to date. The aim of this project was to investigate the orbital forcing of cyclic deposits in the tropical and subtropical North Atlantic during the global carbon cycle perturbation known as the Cenomanian/Turonian Oceanic Anoxic Event (OAE 2). The relative changes in XRF element concentrations of Site 1261 (Demerara Rise) in the tropical Pacific were analyzed by spectral analysis and calibrated against published records of the OAE 2 δ13C anomaly, in particular of the Wunstorf section, resulting in the development of a regional cyclostratigraphy at Demerara Rise. The main results of the project can be summarized as follows: (1) At both localities, Wunstorf and Site 1261, the OAE 2 succession is dominated by the frequency of short eccentricity. According to the orbital age models, independently derived at both sites, the duration of the OAE 2 carbon isotope excursion is almost identical and comprises 4.5 to 5 short eccentricity cycles. (2) The sedimentary cycles within OAE 2 are correlative between the two depositional systems in the intra-shelf basin of Europe and at the continental margin of the tropical Atlantic. (3) The “Bottom water oxygenation” Event at Demera Rise and the “Plenus Cold Event” in Europe are not coeval. Although tropical and mid-latitude shelf-sea cooling are orbitally forced feedbacks of OAE 2 related to the frequency of short eccentricity, the SST cooling pulse in the equatorial Atlantic delays the „Plenus Cold Event“ by about 100 kyr. (4) The climatic response to OAE 2 as increased sequestration of atmospheric CO2 was not related to a single event as assumed before, but was strongly mediated by regional boundary conditions and orbitally forced lead-lag relationships.
Publications
- 2011. Orbitally forced feedbacks of Oceanic Anoxic Event 2 – a pulse of climate cooling and ocean ventilation in the tropical Atlantic and temperate shelf sea of Europe. – Symposium: Climate and ocean dynamics of the Cretaceous greenhouse world, Utrecht, January 26-28, 2011, Abstract volume, 33-34
Voigt, S., Brüsch, D., Pälike, H., Friedrich, O.
- 2011. Repeated bottom-water oxygenation during OAE 2: Timing and duration of short-lived benthic foraminiferal repopulation events (Wunstorf, northern Germany). Journal of Micropaleontology, 30, 119-128
Friedrich, O., Voigt, S., Kuhnt, T., Koch, M.
- 2011. Simulating the biogeochemical effects of volcanic CO2 degassing on the oxygen-state of the deep ocean during the Cenomanian/Turonian Anoxic Event (OAE 2). Earth and Planetary Science Letters, 305, 371-384
Flögel, S., Wallmann, K., Poulsen, C.J., Zhou, J., Oschlies, A., Voigt, S., Kuhnt, W.
