The Wunstorf Drilling Project: Coring a Global Stratigraphic Reference Section of the Oceanic Anoxic Event 2

Abstract

The mid-Cretaceous greenhouse world (Albian–Turonian) was characterized by high atmospheric carbon dioxide levels, much higher global temperatures than at present, and and a lack of permanent ice caps at the poles (Bice et al., 2006; Huber et al., 2002; Wilson et al., 2002). A characteristic feature of this greenhouse world was the deposition of black shales during the Cenomanian / Turonian boundary interval (CTBI; Schlanger and Jenkyns, 1976; Arthur et al., 1990). These carbon-rich sediments reflect a major perturbation of-rich sediments reflect a major perturbation ofrich sediments reflect a major perturbation of the global carbon cycle, with an associated global Ocean Anoxic Event (OAE 2). Despite twenty years of research, thetwenty years of research, the years of research, the OAE 2 still remains critical for the understanding of some of the mechanisms driving the climate and ocean systems during this period of extreme warmth. Numerous Deep Sea Drilling Project (DSDP) and Ocean Drilling Program (ODP) sites and many on-shore sections throughout the world have recovered sediments of CTBI age. However, many of theseHowever, many of theseany of these CTBI records and OAE 2 suffer from relatively poor stratigraphic control, which greatly reduces the options to which greatly reduces the options towhich greatly reduces the options togreatly reduces the options toes the options to the options to correlate paleotemperatures and carbon isotope records to micro- and macropaleontological findings on a high-resolution scale. In order to fill this gap, an onshore drilling project, funded by the Deutsche Forschungsgemeinschaft (DFG), has been initiated. In March 2006, an 80-m-long-m-longm-long-longlong core, covering the CTBI, has been successfully recovered near Wunstorf (20 km east of Hannover, Germany, Fig. 1). The easily accessible Wunstorf section is a highly expanded, middle Cenomanian to Cenomanian toCenomanian to earlyTuroniansuccessionexposingathick TuroniansuccessionexposingathickTuronian succession exposing a thick black shale sequence. The Wunstorf drilling site was placed next to a former quarry which supplied abundant and well preserved macro- and microfossils. The Wunstorf drilling project aims at establishing a high resolution stable isotope record for the black shale succes-sion (OAE 2) of the CTBI and developinging this into a globally applicable high resolu-tion bio- and chemostratigraphic reference section. Disciplines involved include micropaleontology (calcareous nannofossils, planktonic foraminifera), macro-paleontology (ammonites, inoceramids), stable isotopes and cyclostratigraphy mainly based on borehole logging, multi sensor core logging, and x-ray fluorescence (XRF) scanning and x-ray fluorescence (XRF) scanning data. The combination of geochemical, paleontological, and and logging data will allow high resolution chemo- and biostra-tigraphy for the CTBI which may in the future serve as an which may in the future serve as anthe future serve as anfuture serve as an international standard.