| Title: | Evidence for rapid climate cooling during positive d13C excursions within the Middle and Late Cenomanian derived from oxygen isotope data of brachiopods and belemnites |
| Author: | Silke Voigt |
| Date Submitted: | 04/29/2002 |
| Address: | Zülpicher Str. 49a
Cologne
Germany
50674
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| Phone: | |
| Email: | silke.voigt@uni-koeln.de |
| Co-Authors: | Gale, Andrew, S, School of Earth and Environmental Sciences, University of Greenwich |
| Affiliation: | Geological Institute, University of Cologne |
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| Abstract URL: | http://cis.whoi.edu/science/GG/ccod/viewAbstracts.cfm?RefNumber=19725508 |
| Keywords: | Cenomanian, oxygen isotopes, carbon isotopes, brachiopods, palaeotemperature, climate cooling |
| Abstract: | The Cenomanian time interval is considered to be the warmest period in the mid-Cretaceous greenhouse earth, and is additionally characterised by two positive  -excursions within the Middle Cenomanian A. rhotomagense and the Upper Cenomanian M. geslineanum Zones. Both -excursions reflect perturbations of the global carbon cycle, and are associated with brief occurrences of the boreal belemnite Praeactinocamax as transgressive pulse fauna within the North European Province. New  -data of well-preserved terebratulid and rhynchonellid brachiopods and belemnites from sections in southern England (Southerham, Eastbourne) exhibit the first high-resolution palaeotemperature record covering the Early Cenomanian to Early Turonian time. The long-term record of brachiopod- values shows a continuous trend of climate warming from 14.4 °C in the Middle Cenomanian to 20.3 °C in the Lower Turonian. Superimposed on this long-term trend, periods of very rapid cooling occurred in relation to the Middle and Late Cenomanian -Events. The Middle Cenomanian -increase is predated by a rapid increase (-1.5 to -0.2  ) corresponding to a sea-level fall within the C. inerme Subzone. Maximum values (0.5 ) are reached with the onset of transgression in the basal T. costatus Subzone and the occurrence of P. primus. A similar pattern is visible during the Upper Cenomanian -excursion. values of brachiopods and belemnites indicate rapid cooling during a sea-level fall followed by subsequent warming after transgression and the short-termed occurrence of P. plenus. Within both Cenomanian events, the decrease of sea-floor temperatures has a similar magnitude, and are about 8 °C if no changes in of seawater are considered. The linkage of rapid increases with sea-level falls and with the south-spread of boreal taxa suggests that climate cooling could have been coupled to the build-up of ice-sheets and changes in ocean circulation, and could have initiated perturbations within the global carbon cycle. |
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