f Which equations to pick: a comparison of equations for calculating marine organic carbon deposition

Any quantitative description of a geological process requires a mathematical model describing the relevant processes, as well as values for the input parameters. The processes involved in the deposition and preservation of marine organic matter include the flux of the primary produced organic matter from the sea surface to the sea floor, burial efficiency of the material that reaches the bed, and finally the amount of total marine organic carbon that is preserved in the deposit. These three processes are commonly modelled using empirical equations, mostly derived from fits to modern data sets. A range of equations exists for each process, derived by different authors from different data sets (although older data sets are commonly included in newer derivations). This means that a range of answers can be expected when using different combinations of equations to describe marine organic carbon deposition in a given area. The input parameters for equations describing these processes are primary productivity, water depth, sedimentation rate, and oxygen conditions at the bed. For present-day simulations, input parameters are available from measurements. This is unfortunately not the case for simulations of the geological past, but in this case they can be estimated from data measured in cores. The parameter estimation can be done using the same empirical equations as used for the process descriptions. As a range of equations exists, again a range of estimated values can be expected.Several equations and combinations of equations were used to investigate the range of answers that different approaches give. The different equations were used in a Monte Carlo simulation of the calculation of marine organic carbon values, to estimate values of primary productivity with published core data (other input parameters were obtained from the core measurements), and to simulate the spatial distribution of marine organic matter with the forward model OF-Mod (Organic Facies Model).<br>