Regional Variations in the Spreading-Rate Dependence of Abyssal Hill Roughness as Indicators of Mantle Heterogeneity

Abstract

Abyssal hills are potential proxy records of mid-ocean ridge faulting and volcanism, as well as the spreading rates and mantle properties that influence these processes. Satellite gravity-based global prediction of abyssal hill root-mean-square (RMS) heights could provide such a proxy, but are broadly influenced off-axis by pelagic sediment cover, which can lower their values by preferentially filling lows. Here I formulate a sediment-corrected RMS height prediction by estimating an empirical relationship between mean RMS and sediment thickness as a function of spreading rate. I utilize these values to investigate regional variations in the spreading-rate dependence of mean RMS across eight regions world-wide, focusing on half spreading rates <40 mm/yr where spreading rate dependence is strongest. I find that regional variations in this relationship are significant, likely indicating heterogeneity in mantle properties between the different regions.