CENOSTORE

The intensification of the global glacial-interglacial cycle at the onset of the Quaternary (~2.6 Ma) was a critical tipping-point in Earth's recent climate history. The increased severity of cold conditions at the Plio-Pleistocene boundary triggered the development of large-scale continental ice sheets in the Northern Hemisphere. Since then, the North Sea Basin (NSB) experienced multiple glacial-interglacial cycles in terrestrial and shallow marine settings. Unlike the onshore record, the NSB uniquely preserves an almost complete record of glacial erosion and deposition from European ice sheets, as well as sediment input from large rivers systems. This dynamic growth and retreat of ice sheets bordering the NSB, and its subsidence history, have resulted in a thick Quaternary sedimentary sequence containing a detailed stratigraphic record of Northern Hemisphere environmental change. Relatively little is known about global Quaternary ice sheet fluctuations except for estimates on global ice volume with poor chronological control. There is evidence that Quaternary ice sheets generated strong feedback loops that subsequently affected the evolution of the global climate system through complex ocean-atmosphere-cryosphere linkages. Thus, the Quaternary sedimentary sequence preserved in the North Sea is a significant palaeo-climate archive capturing environmental changes across millions of years. As the NSB is a mature petroleum basin, it is covered by extensive seismic and borehole data. The NSB is covered by the North Sea which is a shallow (generally <120 m deep) epicontinental sea, deepening towards its northern margin and the Norwegian Channel. The bathymetry requires drilling using a Mission Specific Platform such as a jack-up rig, generally limited to water depths shallower than 120 m.

We propose to create a suite of virtual site surveys that push the Quaternary understanding of the NSB by incorporating the wealth of new data and models that have arisen over the past five years since the GLACISTORE proposal. These new data and models provide a much firmer basis for testing overarching hypotheses on climate evolution, drivers and feedbacks and the implications of the late Cenozoic succession for CO2 containment. The new data include some 130,000 km2 of 3D seismic data and many hundreds of boreholes (mainly cuttings and geophysical logs available in the Late Cenozoic). Additionally, recent studies have outlined the main Pleistocene depocentres for the NSB and provide an excellent starting point for determining potential locations for drill sites.

The main aim of CenoStore is to recover the highest resolution Quaternary deep shelf record of mid- to mid-high latitude climatic and environmental variation in the eastern Hemisphere. The aim of this virtual site survey is therefore to identify zones of high sediment accumulation rates and stratigraphic completeness in the mud prone lower clinothem slope positions away from submarine channels and fans (readily detectable on 3D seismic attribute maps) with key objectives to: 1) Identify zones (3D areas) of suitable drilling targets in terms of water- and subsurface depth, stratigraphic time, thickness and facies. 2) Construct stratigraphically bound maps of drilling hazards associated with shallow gas or boulders. 3) Identify sites that optimally address scientific objectives (a) whilst being accessible to safely recover in terms of hazards (b) and licensing and infrastructure restrictions.

With almost continuous 3D seismic coverage and hundreds of exploration borehole records, the site selection will be very well constrained in terms of target zones and exclusion zones due to hazards, leading to very low risk and high reward sites with a predictable stratigraphic range and completeness, ideal for palaeo-climate reconstructions.