Latitudinal Differential Response of the Land Plant Ecosystem to
the Cenomanian/Turonian Oceanic Anoxic Event:
Implications for the Global Carbon Budget
Dirk-Jan H. Simons1,*, Fabien Kenig1, Miquel A.Gonzalez-Meler1, and Jaap Sinninghe Damsté2
1
University of Illinois at Chicago, Department of Earth and Environmental Sciences845 W. Taylor Street, M/C 186, Chicago, IL 60607, USA. E-mail:
fkenig@uic.edu2
Netherlands Institute for Sea Research (NIOZ), Department of Marine Biogeochemistry and ToxicologyPO Box 59, 1790 AB, Den Burg, Texel, The Netherlands
*
Present address: Argonne National Laboratory, Carbon Chemistry Group9700 S. Cass Avenue, Argonne, IL 60439, USA. E-mail:
dirkjan_simons@hotmail.com
The positive carbon isotope excursion associated with the Cenomanian-Turonian (C/T) boundary (~93 Ma BP) reflects an increased burial rate of 13C depleted organic carbon at the onset and during an oceanic anoxic event (OAE). A concomitant drop in atmospheric pCO2 of 20% to 40-80% has been estimated previously. We present stable carbon isotopic data on long-chain n-alkanes, derived from terrestrial plants, isolated from marine sediments of two Cenomanian-Turonian sections of the Western Interior Seaway (WIS) at paleolatitudes 35°N and 55°N. Our results deliver compelling evidence for a differential latitudinal response of the land plant ecosystem to the C/T OAE. A change in the land plant ecosystem during the C/T OAE was observed at 35°N, but occurred later than at 10°N. On the contrary, a shift in the vegetation pattern is not observed at 55°N. Towards the end of the OAE, the terrestrial ecosystem at 35°N returns progressively to the previous isotope Cretaceous characteristics. The observed shift in the ecosystem bares characteristics of the evolution of a temporary dominant novel photosynthetic pathway driven by considerable environmental change, similar to the C3/C4 type crossover function.