We have compared the rock-magnetic characteristics of Cretaceous subma
rine basaltic glass (SBG) from DSDP/ODP Holes 417D, 418A, 807C and 543
A to data from Holocene glasses from the East Pacific Rise. Both group
s are very similar in that they contain single-domain, low-Ti magnetit
e as the carrier of a strong and stable remanent magnetization. The be
haviour of magnetic hysteresis in SBG is, however, dominated by superp
aramagnetic grain-size populations. Transmission electron microscopy r
evealed spherically shaped grains of 10-20 nm diameter with crystal la
ttice properties consistent with magnetite. These grains could be resp
onsible for the magnetic behaviour of SBG.