Remanent magnetization of the Upper‐Miocene ‘Blue’ sandstones of California

A study has been made of the magnetization of some upper‐Miocene sediments of California. Field evidence and laboratory experiments indicate that the main component of magnetization of these sediments was not acquired by alignment of detrital magnetic grains at the time of deposition, nor is it due to a later isothermal magnetization of these grains. A strong and stable magnetization appears to have developed through post‐depositional and, in some cases, post‐deiorrnational growth of crystalline magnetic minerals in situ.