Red clay on Bermuda

At http://phys.org/print267336872.html … is an interesting snippet of information from a paper in the Journal of Geophysical Research (doi:10.1029/2012JF002366) and this is that red iron rich clayer soil is found on Bermuda – but the origin is a mystery. The soil overlies carbonate rocks and it is possible dissolution of the carbonate rocks helped produce the clay beds. However, Bermuda sits in a position that might have been affected by the Mississippi river system, bringing down soil from inner North America. It may also have been the remnants of dust from the Sahara – or a desert somewhere in Africa, blown on the wind across the Atlantic. It was decided, after modelling, the latter was the most likely origin – but an extraterrestrial source of the iron, we might imagine, was not part of the study, or the model. Have they really solved the mystery?