palaeosecular
/ˌpalɪəʊˈsɛkjʊlə/ /ˌpeɪlɪəʊˈsɛkjʊlə/Geology
adjective
Of or relating to slow and long-lasting changes in the orientation of the Earth's magnetic field in the geological past. Chiefly in palaeosecular variation.
Origin
1960s; earliest use found in Journal of Geophysical Research. From palaeo- + secular.