Secular variation from Mexican stalagmites: their potential and problems

As part of a feasibility study to see whether stalagmites could provide useful records of secular variation, nine oriented stalagmites were collected from the states of Chiapas and San Luis Potosí, Mexico. Of these, six have yielded measurable natural remanent magnetizations (NRMs) throughout their length. The cleaned magnetizations of one of these samples were shown unequivocally to have recorded the ambient field, and there is no reason to …