Oriented paleomagnetic samples are collected in the field using a rock core drill, or as hand samples (chunks broken off the rock face).To average out sampling errors, a minimum of three samples is taken from each sample site.This provides the rate in meters per million years which is usually rewritten in terms of millimeters per year (which is the same as kilometers per million years).

geomagnetic stratigraphic dating-64

Magnetostratigraphy is a geophysical correlation technique used to date sedimentary and volcanic sequences.

The method works by collecting oriented samples at measured intervals throughout the section.

Failing that, one can tie a polarity to a biostratigraphic event that has been correlated elsewhere with isotopic ages.

With the aid of the independent isotopic age or ages, the local magnetostratigraphic column is correlated with the Global Magnetic Polarity Time Scale (GMPTS).

The direction of the remnant magnetic polarity recorded in the stratigraphic sequence can be used as the basis for the subdivision of the sequence into units characterized by their magnetic polarity.

Such units are called "magnetostratigraphic polarity units" or chrons.Knowing the depth of a hydrocarbon source rock beneath the basin-filling strata allows calculation of the age at which the source rock passed through the generation window and hydrocarbon migration began.Because the ages of cross-cutting trapping structures can usually be determined from magnetostratigraphic data, a comparison of these ages will assist reservoir geologists in their determination of whether or not a play is likely in a given trap.Magnetic orientations of all samples from a site are then compared and their average magnetic polarity is determined with directional statistics, most commonly Fisher statistics or bootstrapping.The statistical significance of each average is evaluated.Spacing of the sample sites within a stratigraphic section depends on the rate of deposition and the age of the section.