Understanding the Origin of Patterned Silica Diagenetic Reaction Fronts

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A chemical reaction boundary is a layer that forms between the initial chemical reactants and final products of a reaction. As the reaction develops the boundary propagates through a chemical mixture. Reaction boundaries have been documented at atomic (nanometer) scale in the laboratory upto metre-scale in sedimentary rocks. They form patterns and patterned reaction boundaries and the processes by which they form are widely studied, since they are found in chemical, biological and geological systems. Chemical processes are very important in changing sediment into rock and for driving fluids out of sediment. Most studies involve looking at how chemical boundaries form at a centimentre scale - but we have identified patterned reaction boundaries at kilometre-scale in sedimentary rocks and want to find out how they form. This has not been attempted before. We have started to document the largest scale chemical reaction boundaries yet to be seen on the globe. They form patterns which consist of cell or ridge-type networks over 10s of square kilometres. The cells are in 50-200 m in height and up to 2.7 km across. The development of the reaction fronts and the patterns are linked to a host of other geological phenomena and the reaction fronts appear to be a fundamental aspect of sedimentary basin evolution. We have three theories as to how the patterns form, this proposal would allow us to refine where exactly IODP borehole should be positioned to find out which - if any - of our theories is correct. Our work can be divided into two parts: 1. We would analyse seismic reflection datasets provided by the oil and gas industry and through a partnership with StatoilHydro we would establish where IODP boreholes should be located. This research would result in the submission of pre- and full-IODP drilling proposals. 2. The data would allow us to evaluate the risk of encoutering shallow gas or hydrocarbons as well as the chances of slope instability. We would compile a comprehensive assessment of this, therefore our IODP proposal would not require any additional and costly data collection.