MODELING GLOBAL RIDGE PRODUCTION FROM THE OBSERVABLE RECORD

The current area/age as a function of age distribution of the oceanic lithosphere imposes interesting bounds on models of the past history of global plate production. Rowley (2002) used the current distribution of area/age as a function of age demonstrate three important points. One, there is no bias, really no systematic correlation between the current rates of subduction of lithosphere of various ages and the areal extent of those ages. This is completely in line with a model in which subduction zones subduct randomly in age and a random amount of those ages per unit time with the total subducted per unit time equal to the global production. Two, there is a remarkable fit, with slope of 1.00 and R-squared of 0.999 between a model of constant rate of plate production and the observed cumulative area of oceanic lithosphere measured at each of the independently dated magnetic reversals used to create the magnetic reversal time scale. Three, there is no evidence of increased rates of ridge production during the Cretaceous or at any other time when preserved ridge length changes are factored in preserved on the Pacific plate. Various ridge production curves have been proposed and have been popular with various modelers of other aspects of earth history. There is nothing in the current area/age as a function of age distribution that requires a constant rate of ridge production. This talk explores what rules would have to exist to have those histories evolve to what we observe to today to demonstrate that although not impossible they are far more complex, involving arbitrary assumptions in order to satisfy current constraints and therefore, following Occum’s Razor, less preferable to the simplest model of constant rate of ridge production.