"the sea floor near mid-ocean ridges revealed polarity reversals, called magnetic striping. This means that the Earth's magnetic field flips every couple hundred thousand years, and magma oozing up from the Earth's interior and solidifying takes on the polarity of the field at the time, creating a record of the inversions."

I've read that the striping only shows up at the ocean surface, but not on the seafloor itself. I read that on the seafloor field intensity is fairly chaotic and they aren't inversions, but just changes in intensity. I could be wrong in what I remember. I think the info was on Mike Fisher's site, newgeology.us