Effect of global warming at the CTBE on mid-latitude vegetation: Insights from palynology and organic-geochemical proxies.
Final Report Abstract
A critical assessment of terrestrial palaeoclimatic proxy records is essential to better understand the impact of mid-Cretaceous extreme warmth on continental environments and ecosystems. This project did focus on spore-pollen assemblages in conjunction with archaeal biomarkers obtained from marine sediments (TEX86) from mid-latitude sites covering the Cenomanian-Turonian boundary event (CTBE). The study was designed to (1) investigate the response of mid-latitude plant communities to the climatic and environmental perturbations associated with the CTBE and to (2) compare the evolution of flora at the onset of the Cretaceous Thermal Maximum with marine temperature records based on TEX86 biomarker proxies. Identifying stratigraphic successions suitable for studying the spore-pollen assemblage across the CTBE is particularly challenging given a lack of stratigraphically wellconstrained continental deposits covering this time interval and a notorious dominance of amorphous organic particles in many marine CTBE black shale records masking any sporepollen signal. For this project, two sites were investigated including marine strata from the Iberian Trough (Central Spain) and from the Southern Provencal Basin (SE France). A third stratigraphic record from the Western Interior Basin (USA) did not yield high enough sporepollen concentrations for a detailed palynofloral analysis. Despite considerable set-backs in the course of the project (incl. critical health status of project scientist, partly insufficient isoGDGT concentrations, unsuitable OM at US site), the project did yield new and important insights into the nature of the vegetation dynamics during the Cenomanian-Turonian hothouse episode. Following high-resolution sampling in outcrop, composite sections were established for both localities based on combined chemo- and biostratigraphy. Characterization of the organic matter was done using bulk and molecular geochemistry, the spore-pollen assemblage were investigated using transmitted-light microscopy. The new results show that despite exceptional global warmth prevailing from the latest Cenomanian onwards, mid-latitude land plant ecosystems were relatively rich and diverse and not affected by significant extinctions. However, the record obtained from France shows distinct variations in the palynological assemblage, which can be correlated with proxy-derived changes in temperature and carbon cycling. Proliferation of eudicot pollen assigned to early fagaleans (Normapolles) is observed during a phase of more dry and cooler climatic conditions known as Plenus Cold Event. In contrast, exceptionally warm (and probably more humid) conditions during the onset and plateau phase of OAE2 carbon isotope excursion did sustain more moisture-adapted vegetation.
Publications
- The neglected story of Oceanic Anoxic Event 2 in the terrestrial realm: A high-resolution multi-proxy study on the mid-latitude Cassis Section in southern France. GeoBerlin, Berlin, Germany, 2015
Cors, J., Heimhofer, U., Adatte, T., Schouten, S.
- Investigating the spatial variability in d13C signatures of bulk rock carbonates – a chemostratigraphic case study from the Cenomanian-Turonian of the Iberian Trough, Spain. GeoTirol, Innsbruck, Austria, 2016
Müller, K., Cors, J., Huck, S., Barroso-Barcenilla, F., Segura, M., Heimhofer, U.
- Continental vegetation and climate dynamics during Oceanic Anoxic Event 2. 10th International Symposium on the Cretaceous, Vienna, Austria, 2017
Heimhofer, U. Wucherpfennig, N., Adatte, T., Schouten, S., Schneebeli-Hermann, E., Gardin, S., Keller, G., Kujau, A.
- Particulate organic matter composition and chemostratigraphy during the onset of Oceanic Anoxic Event 2 (Southern Provence Basin, SE France). GeoBremen, Bremen, 2017
Kentsch, S., Heimhofer, U.
- Response of mid-latitude vegetation to climatic perturbations during OAE2. 33rd IAS Conference, Toulouse France, 2017.
Heimhofer, U. Wucherpfennig, N., Adatte, T., Schouten, S., Schneebeli-Hermann, E., Gardin, S., Keller, G., Kentsch, S., Kujau, A.
- Terrestrial spore-pollen record across the Cenomanian-Turonian hothouse episode. EGU General Assembly, Vienna, Austria, 2017
Heimhofer, U., Wucherpfennig, N., Adatte, T., Schouten, S., Kujau, A.
