The early Eocene climate history displays a suite of rapid global warming events, so-called hyperthermals. This project aims for the first time at deciphering the ecologic impact of these warming events in the mid-latitudinal shallow marine environments of the southern North Sea Basin (the Belgian Kallo-1 core). The results will help understanding the overall biotic impact of global warming in shallow marine environments as well as evaluating ecosystem dynamics under a range of temperature anomalies (1-5 °C).
The first objective is to provide a firm stratigraphic framework and age model for the lower Eocene clays at Kallo, which is needed as the basis for detailed paleoenvironmental reconstructions. Subsequently, high-resolution isotopic (bulk δ13C), biotic (qualitative distribution patterns of marker taxa), and amongst others magnetic susceptibility records will be generated to reveal the exact position of the hyperthermals.
The second objective is to investigate the changes in the depositional and environmental systems through the combination of biotic (quantitative distribution pattern of benthic foraminifera) and geochemical proxies (paleoredox, paleoproductivity and paleothermometry).
This paleoenvironmental study of the Kallo-1 core will contribute to documenting:
- the effects of rapid global warmings on benthic ecosystems, to assessing;
- critical environmental thresholds;
- amplitudes and rates of biotic/environmental changes;
- forcing mechanisms.
This research is intended to lead to a better understanding of the interactions and feedbacks between the geo- and biosphere in shallow-water settings, and to answer the question how early Eocene benthic ecosystems respond to environmental changes during periods of rapid global warming. The study area is located at the southern border of the North Sea Basin, a stratigraphically well-explored region. The nearby ODP deep-sea Site 550 will be used for comparison and age calibration as multiple carbon isotope excursions (CIE’s) are detected there (Cramer et al., 2003).
The project is innovative in terms of the selected time interval and the spatial context, as nearly nothing is known on the presence, the frequency, and the nature of the Early Eocene hyperthermals in the North Sea Basin or mid-latitudinal shallow marine ecosystems in general. Furthermore, this early Eocene setting is to a certain point comparable to the current North Sea configuration, so that results can be extrapolated to the regional context of ongoing global warming. Our ultimate goal is to provide a predictive conceptual model of the biotic impact of rapid climate change.
The second objective is a high-resolution foraminiferal study to detect environmental perturbations as well as ongoing background environmental changes. This microfossil dataset will reveal if threshold behavior (minimum temperature anomaly) is present and how biota responded to scaled changes in depositional or environmental settings, associated with carbon cycle perturbations. The exact levels of biotic change must be assessed in high detail to understand the role of hyperthermals in community restructuring during peak warming or recovery phases. Preliminary results indicate the presence of peculiar biotic disturbances during the Asterigina bartoniana kaasschieteri acme in the studied sequence (I5 event, unpublished master thesis C. Goossens, 2010, KU Leuven). This biotic event is closely related to a bloom in planktic foraminifera, an influx of Nummulites planulatus and a turnover in dinocyst assemblages, and may be linked to the ETM-3 event. Isotopic evidence is needed to verify this hypothesis. The obtained biotic record will be supported by geochemical proxies for paleotemperatures, paleoproductivity and paleooxygenation of the seafloor. This approach is particularly effective in shelf settings with high accumulation rates, which likely yield relevant information pertaining to sea-level dynamics, temperature rise, water column characteristics… and potential lags and leads between them.
